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⚠️ LoopBack 3 is in Maintenance LTS mode, only critical bugs and critical security fixes will be provided. (See Module Long Term Support Policy below.)

We urge all LoopBack 3 users to migrate their applications to LoopBack 4 as soon as possible. Refer to our Migration Guide for more information on how to upgrade.


Browse and test your LoopBack app's APIs.

Basic Usage

Below is a simple LoopBack application. The explorer is mounted at /explorer.

var loopback = require('loopback');
var app = loopback();
var explorer = require('../');
var port = 3000;

var Product = loopback.Model.extend('product');


// Register explorer using component-centric API:
explorer(app, { basePath: '/api', mountPath: '/explorer' });
// Alternatively, register as a middleware:
app.use('/explorer', explorer.routes(app, { basePath: '/api' }));

console.log("Explorer mounted at localhost:" + port + "/explorer");


A note on swagger-ui vulnerabilities

API Explorer for LoopBack 3 is built on top of swagger-ui version 2.x which is no longer maintained. While there are known security vulnerabilities in swagger-ui, we believe they don't affect LoopBack users.

We would love to upgrade our (LB3) API Explorer to v3 of swagger-ui, but unfortunately such upgrade requires too much effort and more importantly addition of new features to LB3 runtime, which would break our LTS guarantees. For more details, see discussion in loopback-component-explorer#263.

npm advisory 985


Versions of swagger-ui prior to 3.0.13 are vulnerable to Cross-Site Scripting (XSS). The package fails to sanitize YAML files imported from URLs or copied-pasted. This may allow attackers to execute arbitrary JavaScript.

LoopBack's API Explorer does not allow clients to import swagger spec from YAML URL/pasted-content. That means loopback-component-explorer IS NOT AFFECTED by this vulnerability.

npm advisory 975


Versions of swagger-ui prior to 3.18.0 are vulnerable to Reverse Tabnapping. The package uses target='_blank' in anchor tags, allowing attackers to access window.opener for the original page. This is commonly used for phishing attacks.

This vulnerability affects anchor tags created from metadata provided by the Swagger spec, for example info.termsOfServiceUrl. LoopBack's API Explorer does not allow clients to provide custom swagger spec, URLs like info.termsOfServiceUrl are fully in control of the LoopBack application developer. That means loopback-component-explorer IS NOT AFFECTED by this vulnerability.

npm advisory 976


Versions of swagger-ui prior to 3.20.9 are vulnerable to Cross-Site Scripting (XSS). The package fails to sanitize URLs used in the OAuth auth flow, which may allow attackers to execute arbitrary JavaScript.

LoopBack 3 API Explorer does not support OAuth auth flow, that means loopback-component-explorer IS NOT AFFECTED by this vulnerability.

GitHub advisory CVE-2019-17495


A Cascading Style Sheets (CSS) injection vulnerability in Swagger UI before 3.23.11 allows attackers to use the Relative Path Overwrite (RPO) technique to perform CSS-based input field value exfiltration, such as exfiltration of a CSRF token value.

Quoting from the disclosure:

We’ve observed that the ?url= parameter in SwaggerUI allows an attacker to override an otherwise hard-coded schema file. We realize that Swagger UI allows users to embed untrusted Json format from remote servers This means we can inject json content via the GET parameter to victim Swagger UI. etc.

LoopBack 3 API Explorer does not suport ?url= parameter, it always loads the Swagger spec file from the LoopBack server serving the Explorer UI. That means loopback-component-explorer IS NOT AFFECTED by this vulnerability.

Upgrading from v1.x

To upgrade your application using loopback-explorer version 1.x, just replace explorer() with explorer.routes() in your server script:

var explorer = require('loopback-component-explorer');  // Module was loopback-explorer in v. 2.0.1 and earlier

// v1.x - does not work anymore
app.use('/explorer', explorer(app, options));
// v2.x
app.use('/explorer', explorer.routes(app, options));

In applications scaffolded by lb app, the idiomatic way is to register loopback-component-explorer in server/component-config.json:

  "loopback-component-explorer": {
    "mountPath": "/explorer"

Advanced Usage

Many aspects of the explorer are configurable.

See options for a description of these options:

// Mount middleware before calling `explorer()` to add custom headers, auth, etc.
app.use('/explorer', loopback.basicAuth('user', 'password'));
explorer(app, {
  basePath: '/custom-api-root',
  uiDirs: [
    path.resolve(__dirname, 'public'),
    path.resolve(__dirname, 'node_modules', 'swagger-ui')
  apiInfo: {
    'title': 'My API',
    'description': 'Explorer example app.'
  resourcePath: 'swagger.json',
  version: '0.1-unreleasable'

In applications scaffolded by lb app, you can edit the server/component-config.json:

  "loopback-component-explorer": {
    "mountPath": "/explorer",
    "apiInfo": {
      "title": "My App",
      "description": "Description of my app APIs.",
      "termsOfServiceUrl": "",
      "contact": "",
      "license": "Apache 2.0",
      "licenseUrl": ""


Options are passed to explorer(app, options).

basePath: String

Default: app.get('restAPIRoot') or '/api'.

Sets the API's base path. This must be set if you are mounting your api to a path different than '/api', e.g. with `loopback.use('/custom-api-root',;

mountPath: String

Default: /explorer

Set the path where to mount the explorer component.

protocol: String

Default: null

A hard override for the outgoing protocol (http or https) that is designated in Swagger resource documents. By default, loopback-component-explorer will write the protocol that was used to retrieve the doc. This option is useful if, for instance, your API sits behind an SSL terminator and thus needs to report its endpoints as https, even though incoming traffic is auto-detected as http.

uiDirs: Array of Strings

Sets a list of paths within your application for overriding Swagger UI files.

If present, will search uiDirs first when attempting to load Swagger UI, allowing you to pick and choose overrides to the interface. Use this to style your explorer or add additional functionality.

See index.html, where you may want to begin your overrides. The rest of the UI is provided by Swagger UI.

apiInfo: Object

Additional information about your API. See the spec.

resourcePath: String

Default: 'resources'

Sets a different path for the resource listing. You generally shouldn't have to change this.

version: String

Default: Read from package.json

Sets your API version. If not present, will read from your app's package.json.

auth: Object

Optional config for setting api access token, can be used to rename the query parameter or set an auth header.

The object has 2 keys:

  • in: either header or query
  • name: the name of the query parameter or header

The default sets the token as a query parameter with the name access_token

Example for setting the api key in a header named x-api-key:

  "loopback-component-explorer": {
    "mountPath": "/explorer",
    "auth": {
      "in": "header",
      "name": "x-api-key"

Module Long Term Support Policy

This module adopts the Module Long Term Support (LTS) policy, with the following End Of Life (EOL) dates:

Version Status Published EOL
6.x Maintenance LTS Apr 2018 Dec 2020
5.x End-of-Life Sep 2017 Dec 2019

Learn more about our LTS plan in docs.