diff --git a/src/v1/image_annotator_client.ts b/src/v1/image_annotator_client.ts
index b0ecd679..81ae76ad 100644
--- a/src/v1/image_annotator_client.ts
+++ b/src/v1/image_annotator_client.ts
@@ -23,6 +23,7 @@ import {
   CallOptions,
   Descriptors,
   ClientOptions,
+  GrpcClientOptions,
   LROperation,
 } from 'google-gax';
 
@@ -70,7 +71,7 @@ export class ImageAnnotatorClient {
    *
    * @param {object} [options] - The configuration object.
    * The options accepted by the constructor are described in detail
-   * in [this document](https://github.com/googleapis/gax-nodejs/blob/master/client-libraries.md#creating-the-client-instance).
+   * in [this document](https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#creating-the-client-instance).
    * The common options are:
    * @param {object} [options.credentials] - Credentials object.
    * @param {string} [options.credentials.client_email]
@@ -93,11 +94,10 @@ export class ImageAnnotatorClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean} [options.fallback] - Use HTTP fallback mode.
-   *     In fallback mode, a special browser-compatible transport implementation is used
-   *     instead of gRPC transport. In browser context (if the `window` object is defined)
-   *     the fallback mode is enabled automatically; set `options.fallback` to `false`
-   *     if you need to override this behavior.
+   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
+   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   *     For more information, please check the
+   *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
    */
   constructor(opts?: ClientOptions) {
     // Ensure that options include all the required fields.
@@ -176,16 +176,29 @@ export class ImageAnnotatorClient {
     };
 
     const protoFilesRoot = this._gaxModule.protobuf.Root.fromJSON(jsonProtos);
-
     // This API contains "long-running operations", which return a
     // an Operation object that allows for tracking of the operation,
     // rather than holding a request open.
-
+    const lroOptions: GrpcClientOptions = {
+      auth: this.auth,
+      grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
+    };
+    if (opts.fallback === 'rest') {
+      lroOptions.protoJson = protoFilesRoot;
+      lroOptions.httpRules = [
+        {
+          selector: 'google.longrunning.Operations.GetOperation',
+          get: '/v1/{name=projects/*/operations/*}',
+          additional_bindings: [
+            {get: '/v1/{name=projects/*/locations/*/operations/*}'},
+            {get: '/v1/{name=operations/*}'},
+            {get: '/v1/{name=locations/*/operations/*}'},
+          ],
+        },
+      ];
+    }
     this.operationsClient = this._gaxModule
-      .lro({
-        auth: this.auth,
-        grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
-      })
+      .lro(lroOptions)
       .operationsClient(opts);
     const asyncBatchAnnotateImagesResponse = protoFilesRoot.lookup(
       '.google.cloud.vision.v1.AsyncBatchAnnotateImagesResponse'
diff --git a/src/v1/product_search_client.ts b/src/v1/product_search_client.ts
index caad8988..b7754050 100644
--- a/src/v1/product_search_client.ts
+++ b/src/v1/product_search_client.ts
@@ -23,6 +23,7 @@ import {
   CallOptions,
   Descriptors,
   ClientOptions,
+  GrpcClientOptions,
   LROperation,
   PaginationCallback,
   GaxCall,
@@ -85,7 +86,7 @@ export class ProductSearchClient {
    *
    * @param {object} [options] - The configuration object.
    * The options accepted by the constructor are described in detail
-   * in [this document](https://github.com/googleapis/gax-nodejs/blob/master/client-libraries.md#creating-the-client-instance).
+   * in [this document](https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#creating-the-client-instance).
    * The common options are:
    * @param {object} [options.credentials] - Credentials object.
    * @param {string} [options.credentials.client_email]
@@ -108,11 +109,10 @@ export class ProductSearchClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean} [options.fallback] - Use HTTP fallback mode.
-   *     In fallback mode, a special browser-compatible transport implementation is used
-   *     instead of gRPC transport. In browser context (if the `window` object is defined)
-   *     the fallback mode is enabled automatically; set `options.fallback` to `false`
-   *     if you need to override this behavior.
+   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
+   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   *     For more information, please check the
+   *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
    */
   constructor(opts?: ClientOptions) {
     // Ensure that options include all the required fields.
@@ -220,16 +220,29 @@ export class ProductSearchClient {
     };
 
     const protoFilesRoot = this._gaxModule.protobuf.Root.fromJSON(jsonProtos);
-
     // This API contains "long-running operations", which return a
     // an Operation object that allows for tracking of the operation,
     // rather than holding a request open.
-
+    const lroOptions: GrpcClientOptions = {
+      auth: this.auth,
+      grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
+    };
+    if (opts.fallback === 'rest') {
+      lroOptions.protoJson = protoFilesRoot;
+      lroOptions.httpRules = [
+        {
+          selector: 'google.longrunning.Operations.GetOperation',
+          get: '/v1/{name=projects/*/operations/*}',
+          additional_bindings: [
+            {get: '/v1/{name=projects/*/locations/*/operations/*}'},
+            {get: '/v1/{name=operations/*}'},
+            {get: '/v1/{name=locations/*/operations/*}'},
+          ],
+        },
+      ];
+    }
     this.operationsClient = this._gaxModule
-      .lro({
-        auth: this.auth,
-        grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
-      })
+      .lro(lroOptions)
       .operationsClient(opts);
     const importProductSetsResponse = protoFilesRoot.lookup(
       '.google.cloud.vision.v1.ImportProductSetsResponse'
diff --git a/src/v1p1beta1/image_annotator_client.ts b/src/v1p1beta1/image_annotator_client.ts
index 9bd68d74..000abd9c 100644
--- a/src/v1p1beta1/image_annotator_client.ts
+++ b/src/v1p1beta1/image_annotator_client.ts
@@ -62,7 +62,7 @@ export class ImageAnnotatorClient {
    *
    * @param {object} [options] - The configuration object.
    * The options accepted by the constructor are described in detail
-   * in [this document](https://github.com/googleapis/gax-nodejs/blob/master/client-libraries.md#creating-the-client-instance).
+   * in [this document](https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#creating-the-client-instance).
    * The common options are:
    * @param {object} [options.credentials] - Credentials object.
    * @param {string} [options.credentials.client_email]
@@ -85,11 +85,10 @@ export class ImageAnnotatorClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean} [options.fallback] - Use HTTP fallback mode.
-   *     In fallback mode, a special browser-compatible transport implementation is used
-   *     instead of gRPC transport. In browser context (if the `window` object is defined)
-   *     the fallback mode is enabled automatically; set `options.fallback` to `false`
-   *     if you need to override this behavior.
+   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
+   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   *     For more information, please check the
+   *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
    */
   constructor(opts?: ClientOptions) {
     // Ensure that options include all the required fields.
diff --git a/src/v1p2beta1/image_annotator_client.ts b/src/v1p2beta1/image_annotator_client.ts
index 5064ae7d..a5d2fdc9 100644
--- a/src/v1p2beta1/image_annotator_client.ts
+++ b/src/v1p2beta1/image_annotator_client.ts
@@ -23,6 +23,7 @@ import {
   CallOptions,
   Descriptors,
   ClientOptions,
+  GrpcClientOptions,
   LROperation,
 } from 'google-gax';
 
@@ -69,7 +70,7 @@ export class ImageAnnotatorClient {
    *
    * @param {object} [options] - The configuration object.
    * The options accepted by the constructor are described in detail
-   * in [this document](https://github.com/googleapis/gax-nodejs/blob/master/client-libraries.md#creating-the-client-instance).
+   * in [this document](https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#creating-the-client-instance).
    * The common options are:
    * @param {object} [options.credentials] - Credentials object.
    * @param {string} [options.credentials.client_email]
@@ -92,11 +93,10 @@ export class ImageAnnotatorClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean} [options.fallback] - Use HTTP fallback mode.
-   *     In fallback mode, a special browser-compatible transport implementation is used
-   *     instead of gRPC transport. In browser context (if the `window` object is defined)
-   *     the fallback mode is enabled automatically; set `options.fallback` to `false`
-   *     if you need to override this behavior.
+   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
+   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   *     For more information, please check the
+   *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
    */
   constructor(opts?: ClientOptions) {
     // Ensure that options include all the required fields.
@@ -160,16 +160,19 @@ export class ImageAnnotatorClient {
     this._protos = this._gaxGrpc.loadProtoJSON(jsonProtos);
 
     const protoFilesRoot = this._gaxModule.protobuf.Root.fromJSON(jsonProtos);
-
     // This API contains "long-running operations", which return a
     // an Operation object that allows for tracking of the operation,
     // rather than holding a request open.
-
+    const lroOptions: GrpcClientOptions = {
+      auth: this.auth,
+      grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
+    };
+    if (opts.fallback === 'rest') {
+      lroOptions.protoJson = protoFilesRoot;
+      lroOptions.httpRules = [];
+    }
     this.operationsClient = this._gaxModule
-      .lro({
-        auth: this.auth,
-        grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
-      })
+      .lro(lroOptions)
       .operationsClient(opts);
     const asyncBatchAnnotateFilesResponse = protoFilesRoot.lookup(
       '.google.cloud.vision.v1p2beta1.AsyncBatchAnnotateFilesResponse'
diff --git a/src/v1p3beta1/image_annotator_client.ts b/src/v1p3beta1/image_annotator_client.ts
index 27484b5e..6c373b87 100644
--- a/src/v1p3beta1/image_annotator_client.ts
+++ b/src/v1p3beta1/image_annotator_client.ts
@@ -23,6 +23,7 @@ import {
   CallOptions,
   Descriptors,
   ClientOptions,
+  GrpcClientOptions,
   LROperation,
 } from 'google-gax';
 
@@ -70,7 +71,7 @@ export class ImageAnnotatorClient {
    *
    * @param {object} [options] - The configuration object.
    * The options accepted by the constructor are described in detail
-   * in [this document](https://github.com/googleapis/gax-nodejs/blob/master/client-libraries.md#creating-the-client-instance).
+   * in [this document](https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#creating-the-client-instance).
    * The common options are:
    * @param {object} [options.credentials] - Credentials object.
    * @param {string} [options.credentials.client_email]
@@ -93,11 +94,10 @@ export class ImageAnnotatorClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean} [options.fallback] - Use HTTP fallback mode.
-   *     In fallback mode, a special browser-compatible transport implementation is used
-   *     instead of gRPC transport. In browser context (if the `window` object is defined)
-   *     the fallback mode is enabled automatically; set `options.fallback` to `false`
-   *     if you need to override this behavior.
+   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
+   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   *     For more information, please check the
+   *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
    */
   constructor(opts?: ClientOptions) {
     // Ensure that options include all the required fields.
@@ -176,16 +176,25 @@ export class ImageAnnotatorClient {
     };
 
     const protoFilesRoot = this._gaxModule.protobuf.Root.fromJSON(jsonProtos);
-
     // This API contains "long-running operations", which return a
     // an Operation object that allows for tracking of the operation,
     // rather than holding a request open.
-
+    const lroOptions: GrpcClientOptions = {
+      auth: this.auth,
+      grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
+    };
+    if (opts.fallback === 'rest') {
+      lroOptions.protoJson = protoFilesRoot;
+      lroOptions.httpRules = [
+        {
+          selector: 'google.longrunning.Operations.GetOperation',
+          get: '/v1/{name=operations/*}',
+          additional_bindings: [{get: '/v1/{name=locations/*/operations/*}'}],
+        },
+      ];
+    }
     this.operationsClient = this._gaxModule
-      .lro({
-        auth: this.auth,
-        grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
-      })
+      .lro(lroOptions)
       .operationsClient(opts);
     const asyncBatchAnnotateFilesResponse = protoFilesRoot.lookup(
       '.google.cloud.vision.v1p3beta1.AsyncBatchAnnotateFilesResponse'
diff --git a/src/v1p3beta1/product_search_client.ts b/src/v1p3beta1/product_search_client.ts
index 97f649ac..66132d9c 100644
--- a/src/v1p3beta1/product_search_client.ts
+++ b/src/v1p3beta1/product_search_client.ts
@@ -23,6 +23,7 @@ import {
   CallOptions,
   Descriptors,
   ClientOptions,
+  GrpcClientOptions,
   LROperation,
   PaginationCallback,
   GaxCall,
@@ -85,7 +86,7 @@ export class ProductSearchClient {
    *
    * @param {object} [options] - The configuration object.
    * The options accepted by the constructor are described in detail
-   * in [this document](https://github.com/googleapis/gax-nodejs/blob/master/client-libraries.md#creating-the-client-instance).
+   * in [this document](https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#creating-the-client-instance).
    * The common options are:
    * @param {object} [options.credentials] - Credentials object.
    * @param {string} [options.credentials.client_email]
@@ -108,11 +109,10 @@ export class ProductSearchClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean} [options.fallback] - Use HTTP fallback mode.
-   *     In fallback mode, a special browser-compatible transport implementation is used
-   *     instead of gRPC transport. In browser context (if the `window` object is defined)
-   *     the fallback mode is enabled automatically; set `options.fallback` to `false`
-   *     if you need to override this behavior.
+   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
+   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   *     For more information, please check the
+   *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
    */
   constructor(opts?: ClientOptions) {
     // Ensure that options include all the required fields.
@@ -220,16 +220,25 @@ export class ProductSearchClient {
     };
 
     const protoFilesRoot = this._gaxModule.protobuf.Root.fromJSON(jsonProtos);
-
     // This API contains "long-running operations", which return a
     // an Operation object that allows for tracking of the operation,
     // rather than holding a request open.
-
+    const lroOptions: GrpcClientOptions = {
+      auth: this.auth,
+      grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
+    };
+    if (opts.fallback === 'rest') {
+      lroOptions.protoJson = protoFilesRoot;
+      lroOptions.httpRules = [
+        {
+          selector: 'google.longrunning.Operations.GetOperation',
+          get: '/v1/{name=operations/*}',
+          additional_bindings: [{get: '/v1/{name=locations/*/operations/*}'}],
+        },
+      ];
+    }
     this.operationsClient = this._gaxModule
-      .lro({
-        auth: this.auth,
-        grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
-      })
+      .lro(lroOptions)
       .operationsClient(opts);
     const importProductSetsResponse = protoFilesRoot.lookup(
       '.google.cloud.vision.v1p3beta1.ImportProductSetsResponse'
diff --git a/src/v1p4beta1/image_annotator_client.ts b/src/v1p4beta1/image_annotator_client.ts
index b91375b9..958e1b3a 100644
--- a/src/v1p4beta1/image_annotator_client.ts
+++ b/src/v1p4beta1/image_annotator_client.ts
@@ -23,6 +23,7 @@ import {
   CallOptions,
   Descriptors,
   ClientOptions,
+  GrpcClientOptions,
   LROperation,
 } from 'google-gax';
 
@@ -70,7 +71,7 @@ export class ImageAnnotatorClient {
    *
    * @param {object} [options] - The configuration object.
    * The options accepted by the constructor are described in detail
-   * in [this document](https://github.com/googleapis/gax-nodejs/blob/master/client-libraries.md#creating-the-client-instance).
+   * in [this document](https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#creating-the-client-instance).
    * The common options are:
    * @param {object} [options.credentials] - Credentials object.
    * @param {string} [options.credentials.client_email]
@@ -93,11 +94,10 @@ export class ImageAnnotatorClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean} [options.fallback] - Use HTTP fallback mode.
-   *     In fallback mode, a special browser-compatible transport implementation is used
-   *     instead of gRPC transport. In browser context (if the `window` object is defined)
-   *     the fallback mode is enabled automatically; set `options.fallback` to `false`
-   *     if you need to override this behavior.
+   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
+   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   *     For more information, please check the
+   *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
    */
   constructor(opts?: ClientOptions) {
     // Ensure that options include all the required fields.
@@ -176,16 +176,25 @@ export class ImageAnnotatorClient {
     };
 
     const protoFilesRoot = this._gaxModule.protobuf.Root.fromJSON(jsonProtos);
-
     // This API contains "long-running operations", which return a
     // an Operation object that allows for tracking of the operation,
     // rather than holding a request open.
-
+    const lroOptions: GrpcClientOptions = {
+      auth: this.auth,
+      grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
+    };
+    if (opts.fallback === 'rest') {
+      lroOptions.protoJson = protoFilesRoot;
+      lroOptions.httpRules = [
+        {
+          selector: 'google.longrunning.Operations.GetOperation',
+          get: '/v1/{name=operations/*}',
+          additional_bindings: [{get: '/v1/{name=locations/*/operations/*}'}],
+        },
+      ];
+    }
     this.operationsClient = this._gaxModule
-      .lro({
-        auth: this.auth,
-        grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
-      })
+      .lro(lroOptions)
       .operationsClient(opts);
     const asyncBatchAnnotateImagesResponse = protoFilesRoot.lookup(
       '.google.cloud.vision.v1p4beta1.AsyncBatchAnnotateImagesResponse'
diff --git a/src/v1p4beta1/product_search_client.ts b/src/v1p4beta1/product_search_client.ts
index 3e8e3479..0626fb3b 100644
--- a/src/v1p4beta1/product_search_client.ts
+++ b/src/v1p4beta1/product_search_client.ts
@@ -23,6 +23,7 @@ import {
   CallOptions,
   Descriptors,
   ClientOptions,
+  GrpcClientOptions,
   LROperation,
   PaginationCallback,
   GaxCall,
@@ -89,7 +90,7 @@ export class ProductSearchClient {
    *
    * @param {object} [options] - The configuration object.
    * The options accepted by the constructor are described in detail
-   * in [this document](https://github.com/googleapis/gax-nodejs/blob/master/client-libraries.md#creating-the-client-instance).
+   * in [this document](https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#creating-the-client-instance).
    * The common options are:
    * @param {object} [options.credentials] - Credentials object.
    * @param {string} [options.credentials.client_email]
@@ -112,11 +113,10 @@ export class ProductSearchClient {
    *     API remote host.
    * @param {gax.ClientConfig} [options.clientConfig] - Client configuration override.
    *     Follows the structure of {@link gapicConfig}.
-   * @param {boolean} [options.fallback] - Use HTTP fallback mode.
-   *     In fallback mode, a special browser-compatible transport implementation is used
-   *     instead of gRPC transport. In browser context (if the `window` object is defined)
-   *     the fallback mode is enabled automatically; set `options.fallback` to `false`
-   *     if you need to override this behavior.
+   * @param {boolean | "rest"} [options.fallback] - Use HTTP fallback mode.
+   *     Pass "rest" to use HTTP/1.1 REST API instead of gRPC.
+   *     For more information, please check the
+   *     {@link https://github.com/googleapis/gax-nodejs/blob/main/client-libraries.md#http11-rest-api-mode documentation}.
    */
   constructor(opts?: ClientOptions) {
     // Ensure that options include all the required fields.
@@ -224,16 +224,25 @@ export class ProductSearchClient {
     };
 
     const protoFilesRoot = this._gaxModule.protobuf.Root.fromJSON(jsonProtos);
-
     // This API contains "long-running operations", which return a
     // an Operation object that allows for tracking of the operation,
     // rather than holding a request open.
-
+    const lroOptions: GrpcClientOptions = {
+      auth: this.auth,
+      grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
+    };
+    if (opts.fallback === 'rest') {
+      lroOptions.protoJson = protoFilesRoot;
+      lroOptions.httpRules = [
+        {
+          selector: 'google.longrunning.Operations.GetOperation',
+          get: '/v1/{name=operations/*}',
+          additional_bindings: [{get: '/v1/{name=locations/*/operations/*}'}],
+        },
+      ];
+    }
     this.operationsClient = this._gaxModule
-      .lro({
-        auth: this.auth,
-        grpc: 'grpc' in this._gaxGrpc ? this._gaxGrpc.grpc : undefined,
-      })
+      .lro(lroOptions)
       .operationsClient(opts);
     const importProductSetsResponse = protoFilesRoot.lookup(
       '.google.cloud.vision.v1p4beta1.ImportProductSetsResponse'