diff --git a/CHANGELOG.md b/CHANGELOG.md
index b437a7bf..ec4dbff7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 - Use Node 22 by default.
 
+## Added
+
+- To all endpoints that depend on collections, add support for a query parameter (GET)
+  or body field (POST) `_collections` that will filter to only those collections, but
+  will not reveal that in link contents. This is controlled by the "ENABLE_COLLECTIONS_AUTHX"
+
 ## [3.11.0] - 2025-03-27
 
 ### Added
diff --git a/README.md b/README.md
index 9f1eed96..503f2c3d 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,7 @@
     - [4.0.0](#400)
       - [Context Extension disabled by default](#context-extension-disabled-by-default)
       - [Node 22 update](#node-22-update)
+      - [Hidden collections filter](#hidden-collections-filter)
     - [3.10.0](#3100)
       - [Node 20 update](#node-20-update)
     - [3.1.0](#310)
@@ -50,6 +51,7 @@
     - [Filter Extension](#filter-extension)
     - [Query Extension](#query-extension)
   - [Aggregation](#aggregation)
+  - [Hidden collections filter for authorization](#hidden-collections-filter-for-authorization)
   - [Ingesting Data](#ingesting-data)
     - [Ingesting large items](#ingesting-large-items)
     - [Subscribing to SNS Topics](#subscribing-to-sns-topics)
@@ -183,6 +185,13 @@ The default Lambda deployment environment is now Node 22.
 To update the deployment to use Node 22, modify the serverless config file value
 `provider.runtime` to be `nodejs22.x` and the application re-deployed.
 
+#### Hidden collections filter
+
+To all endpoints that depend on collections, there is now support for a query parameter
+(GET) or body field (POST) `_collections` that will filter to only those collections, but
+will not reveal that in link contents. This is useful for the application of permissions
+to only certain collections.
+
 ### 3.10.0
 
 #### Node 20 update
@@ -574,7 +583,7 @@ There are some settings that should be reviewed and updated as needeed in the se
 | REQUEST_LOGGING_FORMAT           | Express request logging format to use. Any of the [Morgan predefined formats](https://github.com/expressjs/morgan#predefined-formats).                                                                                                                                          | tiny                                                                                 |
 | STAC_API_URL                     | The root endpoint of this API                                                                                                                                                                                                                                                   | Inferred from request                                                                |
 | ENABLE_TRANSACTIONS_EXTENSION    | Boolean specifying if the [Transaction Extension](https://github.com/radiantearth/stac-api-spec/tree/master/ogcapi-features/extensions/transaction) should be activated                                                                                                         | false                                                                                |
-| ENABLE_CONTEXT_EXTENSION    | Boolean specifying if the [Context Extension](https://github.com/stac-api-extensions/context) should be activated                                                                                                         | false                                                                                |
+| ENABLE_CONTEXT_EXTENSION         | Boolean specifying if the [Context Extension](https://github.com/stac-api-extensions/context) should be activated                                                                                                                                                               | false                                                                                |
 | STAC_API_ROOTPATH                | The path to append to URLs if this is not deployed at the server root. For example, if the server is deployed without a custom domain name, it will have the stage name (e.g., dev) in the path.                                                                                | ""                                                                                   |
 | PRE_HOOK                         | The name of a Lambda function to be called as the pre-hook.                                                                                                                                                                                                                     | none                                                                                 |
 | POST_HOOK                        | The name of a Lambda function to be called as the post-hook.                                                                                                                                                                                                                    | none                                                                                 |
@@ -589,6 +598,7 @@ There are some settings that should be reviewed and updated as needeed in the se
 | CORS_CREDENTIALS                 | Configure whether or not to send the `Access-Control-Allow-Credentials` CORS header. Header will be sent if set to `true`.                                                                                                                                                      | none                                                                                 |
 | CORS_METHODS                     | Configure whether or not to send the `Access-Control-Allow-Methods` CORS header. Expects a comma-delimited string, e.g., `GET,PUT,POST`.                                                                                                                                        | `GET,HEAD,PUT,PATCH,POST,DELETE`                                                     |
 | CORS_HEADERS                     | Configure whether or not to send the `Access-Control-Allow-Headers` CORS header. Expects a comma-delimited string, e.g., `Content-Type,Authorization`. If not specified, defaults to reflecting the headers specified in the request’s `Access-Control-Request-Headers` header. | none                                                                                 |
+| ENABLE_COLLECTIONS_AUTHX         | Enables support for hidden `_collections` query parameter / field when set to `true`.                                                                                                                                                                                                              | none                                                                                 |
 
 Additionally, the credential for OpenSearch must be configured, as decribed in the
 section [Populating and accessing credentials](#populating-and-accessing-credentials).
@@ -1093,6 +1103,32 @@ Available aggregations are:
 - geometry_geohash_grid_frequency ([geohash grid](https://opensearch.org/docs/latest/aggregations/bucket/geohash-grid/) on Item.geometry)
 - geometry_geotile_grid_frequency ([geotile grid](https://opensearch.org/docs/latest/aggregations/bucket/geotile-grid/) on Item.geometry)
 
+## Hidden collections filter for authorization
+
+All endpoints that involve the use of Collections support the use of a "hidden" query
+parameter named  (for GET requests) or body JSON field (for POST requests) named
+`_collections` that can be used by an authorization proxy (e.g., a pre-hook Lambda)
+to filter the collections a user has access to. This parameter/field will be excluded
+from pagination links, so it does not need to be removed on egress.
+
+This feature must be enabled with the `ENABLE_COLLECTIONS_AUTHX` configuration.
+
+The endpoints this applies to are:
+
+- /collections
+- /collections/:collectionId
+- /collections/:collectionId/queryables
+- /collections/:collectionId/aggregations
+- /collections/:collectionId/aggregate
+- /collections/:collectionId/items
+- /collections/:collectionId/items/:itemId
+- /collections/:collectionId/items/:itemId/thumbnail
+- /search
+- /aggregate
+
+The five endpoints of the Transaction Extension do not use this parameter, as there are
+other authorization considerations for these, that are left as future work.
+
 ## Ingesting Data
 
 STAC Collections and Items are ingested by the `ingest` Lambda function, however this Lambda is not invoked directly by a user, it consumes records from the `stac-server-<stage>-queue` SQS. To add STAC Items or Collections to the queue, publish them to the SNS Topic `stac-server-<stage>-ingest`.
diff --git a/package.json b/package.json
index 8bdb475f..29639b72 100644
--- a/package.json
+++ b/package.json
@@ -25,7 +25,7 @@
     "deploy": "sls deploy",
     "sls-remove": "sls remove",
     "package": "sls package",
-    "serve": "REQUEST_LOGGING_FORMAT=dev LOG_LEVEL=debug STAC_API_URL=http://localhost:3000 ENABLE_TRANSACTIONS_EXTENSION=true nodemon --esm ./src/lambdas/api/local.ts",
+    "serve": "REQUEST_LOGGING_FORMAT=dev LOG_LEVEL=debug STAC_API_URL=http://localhost:3000 ENABLE_TRANSACTIONS_EXTENSION=true nodemon --exec node --loader ts-node/esm ./src/lambdas/api/local.ts",
     "build-api-docs": "npx @redocly/cli build-docs src/lambdas/api/openapi.yaml -o ./docs/index.html",
     "prepare": "husky"
   },
diff --git a/src/lambdas/api/app.js b/src/lambdas/api/app.js
index b071f7be..85391f35 100644
--- a/src/lambdas/api/app.js
+++ b/src/lambdas/api/app.js
@@ -6,7 +6,7 @@ import path from 'path'
 import { fileURLToPath } from 'url'
 import database from '../../lib/database.js'
 import api from '../../lib/api.js'
-import { ValidationError } from '../../lib/errors.js'
+import { NotFoundError, ValidationError } from '../../lib/errors.js'
 import { readFile } from '../../lib/fs.js'
 import addEndpoint from './middleware/add-endpoint.js'
 import logger from '../../lib/logger.js'
@@ -153,7 +153,7 @@ app.get('/aggregations', async (req, res, next) => {
 
 app.get('/collections', async (req, res, next) => {
   try {
-    const response = await api.getCollections(database, req.endpoint)
+    const response = await api.getCollections(database, req.endpoint, req.query)
     if (response instanceof Error) next(createError(500, response.message))
     else res.json(response)
   } catch (error) {
@@ -185,7 +185,7 @@ app.post('/collections', async (req, res, next) => {
 app.get('/collections/:collectionId', async (req, res, next) => {
   const { collectionId } = req.params
   try {
-    const response = await api.getCollection(collectionId, database, req.endpoint)
+    const response = await api.getCollection(collectionId, database, req.endpoint, req.query)
     if (response instanceof Error) next(createError(404))
     else res.json(response)
   } catch (error) {
@@ -196,7 +196,9 @@ app.get('/collections/:collectionId', async (req, res, next) => {
 app.get('/collections/:collectionId/queryables', async (req, res, next) => {
   const { collectionId } = req.params
   try {
-    const queryables = await api.getCollectionQueryables(collectionId, database, req.endpoint)
+    const queryables = await api.getCollectionQueryables(
+      collectionId, database, req.endpoint, req.query
+    )
 
     if (queryables instanceof Error) next(createError(404))
     else {
@@ -215,7 +217,9 @@ app.get('/collections/:collectionId/queryables', async (req, res, next) => {
 app.get('/collections/:collectionId/aggregations', async (req, res, next) => {
   const { collectionId } = req.params
   try {
-    const aggs = await api.getCollectionAggregations(collectionId, database, req.endpoint)
+    const aggs = await api.getCollectionAggregations(
+      collectionId, database, req.endpoint, req.query
+    )
     if (aggs instanceof Error) next(createError(404))
     else res.json(aggs)
   } catch (error) {
@@ -231,7 +235,9 @@ app.get('/collections/:collectionId/aggregate',
   async (req, res, next) => {
     const { collectionId } = req.params
     try {
-      const response = await api.getCollection(collectionId, database, req.endpoint)
+      const response = await api.getCollection(
+        collectionId, database, req.endpoint, req.query
+      )
 
       if (response instanceof Error) next(createError(404))
       else {
@@ -249,20 +255,22 @@ app.get('/collections/:collectionId/aggregate',
 app.get('/collections/:collectionId/items', async (req, res, next) => {
   const { collectionId } = req.params
   try {
-    const response = await api.getCollection(collectionId, database, req.endpoint)
+    if ((await api.getCollection(
+      collectionId, database, req.endpoint, req.query
+    )) instanceof Error) {
+      next(createError(404))
+    }
 
-    if (response instanceof Error) next(createError(404))
-    else {
-      const items = await api.searchItems(
+    res.type('application/geo+json')
+    res.json(
+      await api.searchItems(
         collectionId,
         req.query,
         database,
         req.endpoint,
         'GET'
       )
-      res.type('application/geo+json')
-      res.json(items)
-    }
+    )
   } catch (error) {
     if (error instanceof ValidationError) {
       next(createError(400, error.message))
@@ -280,7 +288,7 @@ app.post('/collections/:collectionId/items', async (req, res, next) => {
     if (req.body.collection && req.body.collection !== collectionId) {
       next(createError(400, 'Collection resource URI must match collection in body'))
     } else {
-      const collectionRes = await api.getCollection(collectionId, database, req.endpoint)
+      const collectionRes = await api.getCollection(collectionId, database, req.endpoint, req.query)
       if (collectionRes instanceof Error) next(createError(404))
       else {
         try {
@@ -312,15 +320,14 @@ app.get('/collections/:collectionId/items/:itemId', async (req, res, next) => {
       collectionId,
       itemId,
       database,
-      req.endpoint
+      req.endpoint,
+      req.query
     )
 
-    if (response instanceof Error) {
-      if (response.message === 'Item not found') {
-        next(createError(404))
-      } else {
-        next(createError(500))
-      }
+    if (response instanceof NotFoundError) {
+      next(createError(404))
+    } else if (response instanceof Error) {
+      next(createError(500))
     } else {
       res.type('application/geo+json')
       res.json(response)
@@ -339,7 +346,7 @@ app.put('/collections/:collectionId/items/:itemId', async (req, res, next) => {
     } else if (req.body.id && req.body.id !== itemId) {
       next(createError(400, 'Item ID in resource URI must match id in body'))
     } else {
-      const itemRes = await api.getItem(collectionId, itemId, database, req.endpoint)
+      const itemRes = await api.getItem(collectionId, itemId, database, req.endpoint, req.query)
       if (itemRes instanceof Error) next(createError(404))
       else {
         req.body.collection = collectionId
@@ -372,7 +379,7 @@ app.patch('/collections/:collectionId/items/:itemId', async (req, res, next) =>
     } else if (req.body.id && req.body.id !== itemId) {
       next(createError(400, 'Item ID in resource URI must match id in body'))
     } else {
-      const itemRes = await api.getItem(collectionId, itemId, database, req.endpoint)
+      const itemRes = await api.getItem(collectionId, itemId, database, req.endpoint, req.query)
       if (itemRes instanceof Error) next(createError(404))
       else {
         try {
@@ -418,15 +425,13 @@ app.get('/collections/:collectionId/items/:itemId/thumbnail', async (req, res, n
       collectionId,
       itemId,
       database,
+      req.query
     )
 
-    if (response instanceof Error) {
-      if (response.message === 'Item not found'
-          || response.message === 'Thumbnail not found') {
-        next(createError(404))
-      } else {
-        next(createError(500))
-      }
+    if (response instanceof NotFoundError) {
+      next(createError(404))
+    } else if (response instanceof Error) {
+      next(createError(500))
     } else {
       res.redirect(response.location)
     }
diff --git a/src/lib/api.js b/src/lib/api.js
index 550b9ab0..3e473aa8 100644
--- a/src/lib/api.js
+++ b/src/lib/api.js
@@ -2,7 +2,7 @@ import { pickBy, assign, get as getNested } from 'lodash-es'
 import { DateTime } from 'luxon'
 import { getSignedUrl } from '@aws-sdk/s3-request-presigner'
 import { S3Client, GetObjectCommand } from '@aws-sdk/client-s3'
-import { ValidationError } from './errors.js'
+import { NotFoundError, ValidationError } from './errors.js'
 import { isIndexNotFoundError } from './database.js'
 import logger from './logger.js'
 import { bboxToPolygon } from './geo-utils.js'
@@ -315,9 +315,8 @@ const extractFields = function (params) {
   return fieldRules
 }
 
-const extractIds = function (params) {
+const parseIds = function (ids) {
   let idsRules
-  const { ids } = params
   if (ids) {
     if (typeof ids === 'string') {
       try {
@@ -332,21 +331,18 @@ const extractIds = function (params) {
   return idsRules
 }
 
+const extractIds = function (params) {
+  return parseIds(params.ids)
+}
+
+const extractAllowedCollectionIds = function (params) {
+  return process.env['ENABLE_COLLECTIONS_AUTHX'] === 'true'
+    ? parseIds(params._collections)
+    : undefined
+}
+
 const extractCollectionIds = function (params) {
-  let idsRules
-  const { collections } = params
-  if (collections) {
-    if (typeof collections === 'string') {
-      try {
-        idsRules = JSON.parse(collections)
-      } catch (_) {
-        idsRules = collections.split(',')
-      }
-    } else {
-      idsRules = collections.slice()
-    }
-  }
-  return idsRules
+  return parseIds(params.collections)
 }
 
 export const parsePath = function (inpath) {
@@ -500,7 +496,7 @@ const wrapResponseInFeatureCollection = function (features, links,
   return fc
 }
 
-const buildPaginationLinks = function (limit, parameters, bbox, intersects, endpoint,
+const buildPaginationLinks = function (limit, parameters, bbox, intersects, collections, endpoint,
   httpMethod, sortby, items) {
   if (items.length) {
     const dictToURI = (dict) => (
@@ -518,7 +514,7 @@ const buildPaginationLinks = function (limit, parameters, bbox, intersects, endp
                 }
               }
               value = sortFields.join(',')
-            } else if (p === 'collections') {
+            } else if (p === 'collections') { // TODO
               value = value.toString()
             } else {
               value = JSON.stringify(value)
@@ -544,7 +540,7 @@ const buildPaginationLinks = function (limit, parameters, bbox, intersects, endp
         method: httpMethod,
         type: 'application/geo+json'
       }
-      const nextParams = pickBy(assign(parameters, { bbox, intersects, limit, next }))
+      const nextParams = pickBy(assign(parameters, { bbox, intersects, limit, next, collections }))
       if (httpMethod === 'GET') {
         const nextQueryParameters = dictToURI(nextParams)
         link.href = `${endpoint}?${nextQueryParameters}`
@@ -579,7 +575,11 @@ const searchItems = async function (collectionId, queryParameters, backend, endp
   const filter = extractCql2Filter(queryParameters)
   const fields = extractFields(queryParameters)
   const ids = extractIds(queryParameters)
-  const collections = extractCollectionIds(queryParameters)
+  const allowedCollectionIds = extractAllowedCollectionIds(queryParameters)
+  const specifiedCollectionIds = extractCollectionIds(queryParameters)
+  const collections = allowedCollectionIds ? allowedCollectionIds.filter(
+    (x) => !specifiedCollectionIds || specifiedCollectionIds.includes(x)
+  ) : specifiedCollectionIds
   const limit = extractLimit(queryParameters) || 10
   const page = extractPage(queryParameters)
 
@@ -638,7 +638,15 @@ const searchItems = async function (collectionId, queryParameters, backend, endp
 
   const { results: responseItems, numberMatched, numberReturned } = esResponse
   const paginationLinks = buildPaginationLinks(
-    limit, searchParams, bbox, intersects, newEndpoint, httpMethod, sortby, responseItems
+    limit,
+    searchParams,
+    bbox,
+    intersects,
+    specifiedCollectionIds,
+    newEndpoint,
+    httpMethod,
+    sortby,
+    responseItems
   )
 
   // @ts-ignore
@@ -705,7 +713,11 @@ const aggregate = async function (
   const query = extractStacQuery(queryParameters)
   const filter = extractCql2Filter(queryParameters)
   const ids = extractIds(queryParameters)
-  const collections = extractCollectionIds(queryParameters)
+  const allowedCollectionIds = extractAllowedCollectionIds(queryParameters)
+  const specifiedCollectionIds = extractCollectionIds(queryParameters)
+  const collections = allowedCollectionIds ? allowedCollectionIds.filter(
+    (x) => !specifiedCollectionIds || specifiedCollectionIds.includes(x)
+  ) : specifiedCollectionIds
 
   const searchParams = pickBy({
     datetime,
@@ -977,7 +989,12 @@ const validateAdditionalProperties = (queryables) => {
   }
 }
 
-const getCollectionQueryables = async (collectionId, backend, endpoint = '') => {
+const getCollectionQueryables = async (collectionId, backend, endpoint, queryParameters) => {
+  const allowedCollectionIds = extractAllowedCollectionIds(queryParameters)
+  if (allowedCollectionIds && !allowedCollectionIds.includes(collectionId)) {
+    return new NotFoundError()
+  }
+
   const collection = await backend.getCollection(collectionId)
 
   if (collection instanceof Error) {
@@ -990,7 +1007,12 @@ const getCollectionQueryables = async (collectionId, backend, endpoint = '') =>
   return queryables
 }
 
-const getCollectionAggregations = async (collectionId, backend, endpoint = '') => {
+const getCollectionAggregations = async (collectionId, backend, endpoint, queryParameters) => {
+  const allowedCollectionIds = extractAllowedCollectionIds(queryParameters)
+  if (allowedCollectionIds && !allowedCollectionIds.includes(collectionId)) {
+    return new NotFoundError()
+  }
+
   const collection = await backend.getCollection(collectionId)
 
   if (collection instanceof Error) {
@@ -1123,7 +1145,7 @@ const deleteUnusedFields = (collection) => {
   delete collection.aggregations
 }
 
-const getCollections = async function (backend, endpoint = '') {
+const getCollections = async function (backend, endpoint, queryParameters) {
   // TODO: implement proper pagination, as this will only return up to
   // COLLECTION_LIMIT collections
   const collectionsOrError = await backend.getCollections(1, COLLECTION_LIMIT)
@@ -1131,13 +1153,18 @@ const getCollections = async function (backend, endpoint = '') {
     return collectionsOrError
   }
 
-  for (const collection of collectionsOrError) {
+  const allowedCollectionIds = extractAllowedCollectionIds(queryParameters)
+  const collections = collectionsOrError.filter(
+    (c) => !allowedCollectionIds || allowedCollectionIds.includes(c.id)
+  )
+
+  for (const collection of collections) {
     deleteUnusedFields(collection)
   }
 
-  const linkedCollections = addCollectionLinks(collectionsOrError, endpoint)
+  const linkedCollections = addCollectionLinks(collections, endpoint)
   const resp = {
-    collections: collectionsOrError,
+    collections,
     links: [
       {
         rel: 'self',
@@ -1166,10 +1193,15 @@ const getCollections = async function (backend, endpoint = '') {
   return resp
 }
 
-const getCollection = async function (collectionId, backend, endpoint = '') {
+const getCollection = async function (collectionId, backend, endpoint, queryParameters) {
+  const allowedCollectionIds = extractAllowedCollectionIds(queryParameters)
+  if (allowedCollectionIds && !allowedCollectionIds.includes(collectionId)) {
+    return new NotFoundError()
+  }
+
   const result = await backend.getCollection(collectionId)
   if (result instanceof Error) {
-    return new Error('Collection not found')
+    return new NotFoundError()
   }
 
   deleteUnusedFields(result)
@@ -1191,14 +1223,19 @@ const createCollection = async function (collection, backend) {
   return new Error(`Error creating collection ${collection}`)
 }
 
-const getItem = async function (collectionId, itemId, backend, endpoint = '') {
+const getItem = async function (collectionId, itemId, backend, endpoint, queryParameters) {
+  const allowedCollectionIds = extractAllowedCollectionIds(queryParameters)
+  if (allowedCollectionIds && !allowedCollectionIds.includes(collectionId)) {
+    return new NotFoundError()
+  }
+
   const itemQuery = { collections: [collectionId], id: itemId }
   const { results } = await backend.search(itemQuery, 1)
   const [it] = addItemLinks(results, endpoint)
   if (it) {
     return it
   }
-  return new Error('Item not found')
+  return new NotFoundError()
 }
 
 const partialUpdateItem = async function (
@@ -1241,12 +1278,17 @@ const deleteItem = async function (collectionId, itemId, backend) {
   return new Error(`Error deleting item ${collectionId}/${itemId}`)
 }
 
-const getItemThumbnail = async function (collectionId, itemId, backend) {
+const getItemThumbnail = async function (collectionId, itemId, backend, queryParameters) {
+  const allowedCollectionIds = extractAllowedCollectionIds(queryParameters)
+  if (allowedCollectionIds && !allowedCollectionIds.includes(collectionId)) {
+    return new NotFoundError()
+  }
+
   const itemQuery = { collections: [collectionId], id: itemId }
   const { results } = await backend.search(itemQuery, 1)
   const [item] = results
   if (!item) {
-    return new Error('Item not found')
+    return new NotFoundError()
   }
 
   const thumbnailAsset = Object.values(item.assets || []).find(
@@ -1254,7 +1296,7 @@ const getItemThumbnail = async function (collectionId, itemId, backend) {
   )
 
   if (!thumbnailAsset) {
-    return new Error('Thumbnail not found')
+    return new NotFoundError()
   }
 
   let location
@@ -1279,7 +1321,7 @@ const getItemThumbnail = async function (collectionId, itemId, backend) {
       expiresIn: 60 * 5, // expiry in seconds
     })
   } else {
-    return new Error('Thumbnail not found')
+    return new NotFoundError()
   }
 
   return { location }
diff --git a/src/lib/database.js b/src/lib/database.js
index 17e10b5c..1e027311 100644
--- a/src/lib/database.js
+++ b/src/lib/database.js
@@ -1,7 +1,7 @@
 import { isEmpty } from 'lodash-es'
 import { dbClient as _client, createIndex } from './database-client.js'
 import logger from './logger.js'
-import { ValidationError } from './errors.js'
+import { NotFoundError, ValidationError } from './errors.js'
 import { bboxToPolygon } from './geo-utils.js'
 
 const COLLECTIONS_INDEX = process.env['COLLECTIONS_INDEX'] || 'collections'
@@ -666,7 +666,7 @@ async function getCollection(collectionId) {
   if (Array.isArray(response.body.hits.hits) && response.body.hits.hits.length) {
     return response.body.hits.hits[0]._source
   }
-  return new Error('Collection not found')
+  return new NotFoundError()
 }
 
 // get all collections
diff --git a/src/lib/errors.js b/src/lib/errors.js
index 86e77d81..5a7f0d65 100644
--- a/src/lib/errors.js
+++ b/src/lib/errors.js
@@ -1,7 +1,15 @@
+/* eslint-disable max-classes-per-file */
 /* eslint-disable import/prefer-default-export */
 export class ValidationError extends Error {
   constructor(message) {
     super(message)
-    this.name = 'ValidationError'
+    this.name = this.constructor.name
+  }
+}
+
+export class NotFoundError extends Error {
+  constructor(message) {
+    super(message)
+    this.name = this.constructor.name
   }
 }
diff --git a/src/lib/s3-utils.ts b/src/lib/s3-utils.ts
index fea6c344..cfea2575 100644
--- a/src/lib/s3-utils.ts
+++ b/src/lib/s3-utils.ts
@@ -14,7 +14,7 @@ const getObjectBody = async (s3Location: {bucket: string, key: string}) => {
     return result.Body
   } catch (error) {
     if (error instanceof Error) {
-      console.log(`Failed to fetch ${s3Location.bucket}/${s3Location.key}: ${error.message}`)
+      console.error(`Failed to fetch ${s3Location.bucket}/${s3Location.key}: ${error.message}`)
     }
     throw error
   }
diff --git a/tests/system/test-api-collection-items-get.js b/tests/system/test-api-collection-items-get.js
index 0969ae43..d7f88690 100644
--- a/tests/system/test-api-collection-items-get.js
+++ b/tests/system/test-api-collection-items-get.js
@@ -91,3 +91,25 @@ test('GET /collections/:collectionId/items for non-existent collection returns 4
 
   t.is(response.statusCode, 404)
 })
+
+test('GET /collections/:collectionId/items with restriction returns filtered collections', async (t) => {
+  const { collectionId } = t.context
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const path = `collections/${collectionId}/items`
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    {
+      resolveBodyOnly: false,
+      searchParams: { _collections: `${collectionId},foo,bar` }
+    })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false,
+      throwHttpErrors: false,
+      searchParams: { _collections: 'not-a-collection' }
+    })).statusCode, 404)
+})
diff --git a/tests/system/test-api-get-aggregate.js b/tests/system/test-api-get-aggregate.js
index 33179f71..48a97842 100644
--- a/tests/system/test-api-get-aggregate.js
+++ b/tests/system/test-api-get-aggregate.js
@@ -500,3 +500,93 @@ test('GET /aggregate with aggregations and filter params', async (t) => {
     value: 1
   }])
 })
+
+test('GET /aggregate with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const fixtureFiles = [
+    'collection.json',
+    'LC80100102015050LGN00.json',
+    'LC80100102015082LGN00.json'
+  ]
+  const items = await Promise.all(fixtureFiles.map((x) => loadJson(x)))
+  await ingestItems(items)
+  await refreshIndices()
+
+  const collectionId = 'landsat-8-l1'
+
+  let response = null
+
+  // validate how many items we have total without restricting collections
+  response = await t.context.api.client.get(
+    'aggregate',
+    {
+      searchParams: new URLSearchParams({
+        aggregations: ['total_count']
+      }),
+      resolveBodyOnly: false,
+    }
+  )
+
+  t.is(response.statusCode, 200)
+  t.deepEqual(response.body.aggregations, [{
+    name: 'total_count',
+    data_type: 'integer',
+    value: 4
+  }])
+
+  // get the counts for collectionId without restrictions
+  response = await t.context.api.client.get(
+    'aggregate',
+    {
+      searchParams: new URLSearchParams({
+        aggregations: ['total_count'],
+        collections: [collectionId]
+      }),
+      resolveBodyOnly: false,
+    }
+  )
+
+  t.is(response.statusCode, 200)
+  t.deepEqual(response.body.aggregations, [{
+    name: 'total_count',
+    data_type: 'integer',
+    value: 2
+  }])
+
+  // restrict collections to include the one we just got 2 results for
+
+  const response2 = await t.context.api.client.get(
+    'aggregate',
+    {
+      searchParams: new URLSearchParams({
+        aggregations: ['total_count'],
+        _collections: [collectionId, 'foo', 'bar']
+      }),
+      resolveBodyOnly: false,
+    }
+  )
+
+  t.is(response.statusCode, 200)
+  t.deepEqual(response2.body.aggregations, response.body.aggregations)
+
+  // restrict collections to a non-existent one with no items, so should be 0 results
+  response = await t.context.api.client.get(
+    'aggregate',
+    {
+      searchParams: new URLSearchParams({
+        aggregations: ['total_count'],
+        collections: [collectionId],
+        _collections: ['not-a-collection']
+      }),
+      resolveBodyOnly: false,
+    }
+  )
+
+  t.is(response.statusCode, 200)
+  t.deepEqual(response.body.aggregations, [{
+    name: 'total_count',
+    data_type: 'integer',
+    value: 0
+  }])
+})
diff --git a/tests/system/test-api-get-collection-aggregate.js b/tests/system/test-api-get-collection-aggregate.js
index aea438fd..d3f8e58c 100644
--- a/tests/system/test-api-get-collection-aggregate.js
+++ b/tests/system/test-api-get-collection-aggregate.js
@@ -167,3 +167,26 @@ test('GET /aggregate with aggregation not supported by this collection', async (
     description: 'Aggregation grid_code_frequency not supported by collection sentinel-1-grd'
   })
 })
+
+test('GET /collections/:collectionId/aggregate with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const collectionId = 'landsat-8-l1'
+
+  const path = `collections/${collectionId}/aggregate`
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    {
+      resolveBodyOnly: false,
+      searchParams: { _collections: `${collectionId},foo,bar` }
+    })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false,
+      throwHttpErrors: false,
+      searchParams: { _collections: 'not-a-collection' }
+    })).statusCode, 404)
+})
diff --git a/tests/system/test-api-get-collection-aggregations.js b/tests/system/test-api-get-collection-aggregations.js
index c4dd1c23..75d8781f 100644
--- a/tests/system/test-api-get-collection-aggregations.js
+++ b/tests/system/test-api-get-collection-aggregations.js
@@ -129,3 +129,26 @@ test('GET /collections/:collectionId/aggregations returns default aggregations f
     ])
     t.deepEqual(response.body.links, links(proto, host, collectionId))
   })
+
+test('GET /collections/:collectionId/aggregations with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const { collectionId } = t.context
+
+  const path = `collections/${collectionId}/aggregations`
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    {
+      resolveBodyOnly: false,
+      searchParams: { _collections: `${collectionId},foo,bar` }
+    })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false,
+      throwHttpErrors: false,
+      searchParams: { _collections: 'not-a-collection' }
+    })).statusCode, 404)
+})
diff --git a/tests/system/test-api-get-collection-queryables.js b/tests/system/test-api-get-collection-queryables.js
index 74df64da..bf818931 100644
--- a/tests/system/test-api-get-collection-queryables.js
+++ b/tests/system/test-api-get-collection-queryables.js
@@ -111,3 +111,26 @@ test.only('GET /collection/:collectionId/queryables for collection with unsuppor
   t.regex(error.response.body.description,
     /.*Unsupported additionalProperties value: "false". Must be set to "true".*/)
 })
+
+test('GET /collections/:collectionId/queryables with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const { collectionId } = t.context
+
+  const path = `collections/${collectionId}/queryables`
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    {
+      resolveBodyOnly: false,
+      searchParams: { _collections: `${collectionId},foo,bar` }
+    })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false,
+      throwHttpErrors: false,
+      searchParams: { _collections: 'not-a-collection' }
+    })).statusCode, 404)
+})
diff --git a/tests/system/test-api-get-collection.js b/tests/system/test-api-get-collection.js
index 93f8444c..8fc5bb33 100644
--- a/tests/system/test-api-get-collection.js
+++ b/tests/system/test-api-get-collection.js
@@ -59,3 +59,24 @@ test('GET /collection/:collectionId for non-existent collection returns Not Foun
 
   t.is(response.statusCode, 404)
 })
+
+test('GET /collections/:collectionId with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const { collectionId } = t.context
+
+  t.is((await t.context.api.client.get(`collections/${collectionId}`,
+    { resolveBodyOnly: false })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(`collections/${collectionId}`,
+    {
+      resolveBodyOnly: false,
+      searchParams: { _collections: `${collectionId},foo,bar` }
+    })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(`collections/${collectionId}`,
+    { resolveBodyOnly: false,
+      throwHttpErrors: false,
+      searchParams: { _collections: 'not-a-collection' }
+    })).statusCode, 404)
+})
diff --git a/tests/system/test-api-get-collections.js b/tests/system/test-api-get-collections.js
index 73687dc1..166ae0ba 100644
--- a/tests/system/test-api-get-collections.js
+++ b/tests/system/test-api-get-collections.js
@@ -12,11 +12,11 @@ test.before(async (t) => {
 
   t.context = standUpResult
 
-  const collectionId = randomId('collection')
+  t.context.collectionId = randomId('collection')
 
   const collection = await loadFixture(
     'landsat-8-l1-collection.json',
-    { id: collectionId }
+    { id: t.context.collectionId }
   )
 
   await ingestItem({
@@ -49,3 +49,36 @@ test('GET /collections has a content type of "application/json', async (t) => {
 
   t.is(response.headers['content-type'], 'application/json; charset=utf-8')
 })
+
+test('GET /collections with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  await refreshIndices()
+
+  const { collectionId } = t.context
+
+  // disable collections filtering
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'not true'
+
+  t.is((await t.context.api.client.get(
+    'collections', {
+      searchParams: { _collections: 'not-a-collection' } }
+  )
+  ).collections.length, 1)
+
+  // enable collections filtering
+
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  t.is((await t.context.api.client.get(
+    'collections', {
+      searchParams: { _collections: `${collectionId},foo,bar` } }
+  )
+  ).collections.length, 1)
+
+  t.is((await t.context.api.client.get(
+    'collections', {
+      searchParams: { _collections: 'not-a-collection' } }
+  )
+  ).collections.length, 0)
+})
diff --git a/tests/system/test-api-item-get.js b/tests/system/test-api-item-get.js
index 64c442d5..c95ed332 100644
--- a/tests/system/test-api-item-get.js
+++ b/tests/system/test-api-item-get.js
@@ -61,7 +61,7 @@ test('GET /collections/:collectionId/items/:itemId', async (t) => {
   t.is(response.body.collection, collectionId)
 })
 
-test('GET /collections/:collectionId/items/:itemId for a non-existent id returns Not Found"', async (t) => {
+test('GET /collections/:collectionId/items/:itemId for a non-existent id returns not found', async (t) => {
   const { collectionId } = t.context
 
   const response = await t.context.api.client.get(
@@ -71,3 +71,61 @@ test('GET /collections/:collectionId/items/:itemId for a non-existent id returns
 
   t.is(response.statusCode, 404)
 })
+
+test('GET /collections/:collectionId/items/:itemId for a non-existent collection returns not found', async (t) => {
+  const response = await t.context.api.client.get(
+    'collections/DOES_NOT_EXIST/items/DOES_NOT_EXIST',
+    { resolveBodyOnly: false, throwHttpErrors: false }
+  )
+
+  t.is(response.statusCode, 404)
+})
+
+test('GET /collections/:collectionId/items/:itemId with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const { collectionId, itemId } = t.context
+
+  const path = `collections/${collectionId}/items/${itemId}`
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    {
+      resolveBodyOnly: false,
+      searchParams: { _collections: `${collectionId},foo,bar` }
+    })).statusCode, 200)
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false,
+      throwHttpErrors: false,
+      searchParams: { _collections: 'not-a-collection' }
+    })).statusCode, 404)
+})
+
+test('GET /collections/:collectionId/items/:itemId/thumbnail with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const { collectionId, itemId } = t.context
+
+  const path = `collections/${collectionId}/items/${itemId}/thumbnail`
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false, followRedirect: false
+    })).statusCode, 302)
+
+  t.is((await t.context.api.client.get(path,
+    {
+      resolveBodyOnly: false,
+      followRedirect: false,
+      searchParams: { _collections: `${collectionId},foo,bar` }
+    })).statusCode, 302)
+
+  t.is((await t.context.api.client.get(path,
+    { resolveBodyOnly: false,
+      followRedirect: false,
+      throwHttpErrors: false,
+      searchParams: { _collections: 'not-a-collection' }
+    })).statusCode, 404)
+})
diff --git a/tests/system/test-api-search-get.js b/tests/system/test-api-search-get.js
index ab661318..e970bf2c 100644
--- a/tests/system/test-api-search-get.js
+++ b/tests/system/test-api-search-get.js
@@ -142,3 +142,42 @@ test('/search filter, query, and item search in single request', async (t) => {
   })
   t.is(response.features.length, 1)
 })
+
+test('GET /search with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const fixtureFiles = [
+    'catalog.json',
+    'collection.json',
+    'LC80100102015050LGN00.json',
+    'LC80100102015082LGN00.json'
+  ]
+  const items = await Promise.all(fixtureFiles.map((x) => loadJson(x)))
+  await ingestItems(items)
+  await refreshIndices()
+
+  const collectionId = 'landsat-8-l1'
+  const path = 'search'
+
+  const r1 = await t.context.api.client.get(path,
+    { resolveBodyOnly: false })
+
+  t.is(r1.statusCode, 200)
+  t.is(r1.body.features.length, 3)
+
+  const r2 = await t.context.api.client.get(path,
+    { resolveBodyOnly: false,
+      searchParams: { _collections: `${collectionId},foo,bar` }
+    })
+
+  t.is(r2.statusCode, 200)
+  t.is(r2.body.features.length, 2)
+
+  const r3 = await t.context.api.client.get(path,
+    { resolveBodyOnly: false,
+      searchParams: { _collections: 'not-a-collection' }
+    })
+
+  t.is(r3.statusCode, 200)
+  t.is(r3.body.features.length, 0)
+})
diff --git a/tests/system/test-api-search-post.js b/tests/system/test-api-search-post.js
index b74113b9..269d018d 100644
--- a/tests/system/test-api-search-post.js
+++ b/tests/system/test-api-search-post.js
@@ -1360,6 +1360,50 @@ test('/search - filter extension - s_intersects - non-existent geometry type', a
     /.*Operand for 's_intersects' must be a GeoJSON geometry: type was 'notPolygon'*/)
 })
 
+test('POST /search with restriction returns filtered collections', async (t) => {
+  process.env['ENABLE_COLLECTIONS_AUTHX'] = 'true'
+
+  const fixtureFiles = [
+    'collection.json',
+    'LC80100102015050LGN00.json',
+    'LC80100102015082LGN00.json'
+  ]
+  const items = await Promise.all(fixtureFiles.map((x) => loadJson(x)))
+  await ingestItems(items)
+  await refreshIndices()
+
+  const collectionId = 'landsat-8-l1'
+  const urlpath = 'search'
+
+  const r1 = await t.context.api.client.post(urlpath,
+    { resolveBodyOnly: false,
+      json: {
+        _collections: [collectionId]
+      } })
+
+  t.is(r1.statusCode, 200)
+  t.is(r1.body.features.length, 2)
+
+  const r2 = await t.context.api.client.post(urlpath,
+    { resolveBodyOnly: false,
+      json: {
+        _collections: [collectionId, 'foo', 'bar']
+      } })
+
+  t.is(r2.statusCode, 200)
+  t.is(r2.body.features.length, 2)
+
+  const r3 = await t.context.api.client.post(urlpath,
+    { resolveBodyOnly: false,
+      json: {
+        _collections: ['not-a-collection']
+      }
+    })
+
+  t.is(r3.statusCode, 200)
+  t.is(r3.body.features.length, 0)
+})
+
 test('/search - context extension - no context when default', async (t) => {
   const response = await t.context.api.client.post('search', { json: { } })
   t.is(response.type, 'FeatureCollection')