diff --git a/docs/reference.asciidoc b/docs/reference.asciidoc
index 2414962c0..2c47b6d6f 100644
--- a/docs/reference.asciidoc
+++ b/docs/reference.asciidoc
@@ -418,6 +418,9 @@ client.get({ id, index })
 * *Request (object):*
 ** *`id` (string)*: Unique identifier of the document.
 ** *`index` (string)*: Name of the index that contains the document.
+** *`force_synthetic_source` (Optional, boolean)*: Should this request force synthetic _source?
+Use this to test if the mapping supports synthetic _source and to get a sense of the worst case performance.
+Fetches with this enabled will be slower the enabling synthetic source natively in the index.
 ** *`preference` (Optional, string)*: Specifies the node or shard the operation should be performed on. Random by default.
 ** *`realtime` (Optional, boolean)*: If `true`, the request is real-time as opposed to near-real-time.
 ** *`refresh` (Optional, boolean)*: If true, Elasticsearch refreshes the affected shards to make this operation visible to search. If false, do nothing with refreshes.
@@ -606,6 +609,9 @@ client.mget({ ... })
 ** *`index` (Optional, string)*: Name of the index to retrieve documents from when `ids` are specified, or when a document in the `docs` array does not specify an index.
 ** *`docs` (Optional, { _id, _index, routing, _source, stored_fields, version, version_type }[])*: The documents you want to retrieve. Required if no index is specified in the request URI.
 ** *`ids` (Optional, string | string[])*: The IDs of the documents you want to retrieve. Allowed when the index is specified in the request URI.
+** *`force_synthetic_source` (Optional, boolean)*: Should this request force synthetic _source?
+Use this to test if the mapping supports synthetic _source and to get a sense of the worst case performance.
+Fetches with this enabled will be slower the enabling synthetic source natively in the index.
 ** *`preference` (Optional, string)*: Specifies the node or shard the operation should be performed on. Random by default.
 ** *`realtime` (Optional, boolean)*: If `true`, the request is real-time as opposed to near-real-time.
 ** *`refresh` (Optional, boolean)*: If `true`, the request refreshes relevant shards before retrieving documents.
@@ -1030,6 +1036,9 @@ You can exclude fields from this subset using the `_source_excludes` query param
 If the `_source` parameter is `false`, this parameter is ignored.
 ** *`q` (Optional, string)*: Query in the Lucene query string syntax using query parameter search.
 Query parameter searches do not support the full Elasticsearch Query DSL but are handy for testing.
+** *`force_synthetic_source` (Optional, boolean)*: Should this request force synthetic _source?
+Use this to test if the mapping supports synthetic _source and to get a sense of the worst case performance.
+Fetches with this enabled will be slower the enabling synthetic source natively in the index.
 
 [discrete]
 === search_mvt
diff --git a/src/api/types.ts b/src/api/types.ts
index c1912352f..7e10c2933 100644
--- a/src/api/types.ts
+++ b/src/api/types.ts
@@ -372,6 +372,7 @@ export interface GetGetResult<TDocument = unknown> {
 export interface GetRequest extends RequestBase {
   id: Id
   index: IndexName
+  force_synthetic_source?: boolean
   preference?: string
   realtime?: boolean
   refresh?: boolean
@@ -685,6 +686,7 @@ export interface MgetOperation {
 
 export interface MgetRequest extends RequestBase {
   index?: IndexName
+  force_synthetic_source?: boolean
   preference?: string
   realtime?: boolean
   refresh?: boolean
@@ -1145,6 +1147,7 @@ export interface SearchRequest extends RequestBase {
   _source_excludes?: Fields
   _source_includes?: Fields
   q?: string
+  force_synthetic_source?: boolean
   aggregations?: Record<string, AggregationsAggregationContainer>
   /** @alias aggregations */
   aggs?: Record<string, AggregationsAggregationContainer>
diff --git a/src/api/typesWithBodyKey.ts b/src/api/typesWithBodyKey.ts
index 938dc3328..d8bf9523d 100644
--- a/src/api/typesWithBodyKey.ts
+++ b/src/api/typesWithBodyKey.ts
@@ -393,6 +393,7 @@ export interface GetGetResult<TDocument = unknown> {
 export interface GetRequest extends RequestBase {
   id: Id
   index: IndexName
+  force_synthetic_source?: boolean
   preference?: string
   realtime?: boolean
   refresh?: boolean
@@ -710,6 +711,7 @@ export interface MgetOperation {
 
 export interface MgetRequest extends RequestBase {
   index?: IndexName
+  force_synthetic_source?: boolean
   preference?: string
   realtime?: boolean
   refresh?: boolean
@@ -1197,6 +1199,7 @@ export interface SearchRequest extends RequestBase {
   _source_excludes?: Fields
   _source_includes?: Fields
   q?: string
+  force_synthetic_source?: boolean
   /** @deprecated The use of the 'body' key has been deprecated, move the nested keys to the top level object. */
   body?: {
     aggregations?: Record<string, AggregationsAggregationContainer>