open-feature · thomaspoignant · Feb 5, 2026 · Feb 3, 2026 · Feb 4, 2026
@@ -29,6 +29,9 @@ const evaluationCtx: EvaluationContext = {
 
 const goFeatureFlagWebProvider = new GoFeatureFlagWebProvider({
   endpoint: endpoint,
+  customHeadeers: {
+    'User-Agent': "my-app/1.0.0",
+  },
   // ...
 }, logger);
 
@@ -54,6 +57,7 @@ client.addHandler(ProviderEvents.ConfigurationChanged, () => { //... });
 | endpoint                      | string |                | endpoint is the URL where your GO Feature Flag server is located.                                                                                                                               |
 | apiTimeout                    | number | 0 = no timeout | (optional) timeout is the time in millisecond we wait for an answer from the server.                                                                                                            |
 | apiKey                        | string |                | (optional) If GO Feature Flag is configured to authenticate the requests, you should provide an API Key to the provider. Please ask the administrator of the relay proxy to provide an API Key. |
+| customHeaders                 | object |                | (optional) custom headers to be sent for every HTTP request.                                                                                                                                    |
 | websocketRetryInitialDelay    | number | 100            | (optional) initial delay in millisecond to wait before retrying to connect the websocket                                                                                                        |
 | websocketRetryDelayMultiplier | number | 2              | (optional) multiplier of websocketRetryInitialDelay after each failure _(example: 1st connection retry will be after 100ms, second after 200ms, third after 400ms ...)_                         |
 | websocketMaxRetries           | number | 10             | (optional) maximum number of retries before considering the websocket unreachable                                                                                                               |

@@ -15,6 +15,10 @@ describe('Collect Data API', () => {
       endpoint: 'https://gofeatureflag.org',
       apiTimeout: 1000,
       apiKey: '123456',
+      customHeaders: {
+        'User-Agent': 'goff-web/1.0.0',
+        Authorization: 'Bearer foo',
+      },
     };
     const goff = new GoffApiController(options);
     await goff.collectData(
@@ -37,6 +41,7 @@ describe('Collect Data API', () => {
       'Content-Type': 'application/json',
       Accept: 'application/json',
       Authorization: `Bearer ${options.apiKey}`,
+      'User-Agent': 'goff-web/1.0.0',
     });
     expect(fetchMock.lastOptions()?.body).toEqual(
       JSON.stringify({
@@ -62,6 +67,9 @@ describe('Collect Data API', () => {
     const options: GoFeatureFlagWebProviderOptions = {
       endpoint: 'https://gofeatureflag.org',
       apiTimeout: 1000,
+      customHeaders: {
+        'User-Agent': 'goff-web/2.0.0',
+      },
     };
     const goff = new GoffApiController(options);
     await goff.collectData(
@@ -83,6 +91,7 @@ describe('Collect Data API', () => {
     expect(fetchMock.lastOptions()?.headers).toEqual({
       'Content-Type': 'application/json',
       Accept: 'application/json',
+      'User-Agent': 'goff-web/2.0.0',
     });
     expect(fetchMock.lastOptions()?.body).toEqual(
       JSON.stringify({

@@ -42,6 +42,10 @@ export class GoffApiController {
         Accept: 'application/json',
       };
 
+      if (this.options.customHeaders) {
+        Object.assign(headers, this.options.customHeaders);
+      }
+
       if (this.options.apiKey) {
         headers['Authorization'] = `Bearer ${this.options.apiKey}`;
       }

@@ -322,6 +322,10 @@ describe('GoFeatureFlagWebProvider', () => {
           apiTimeout: 1000,
           maxRetries: 1,
           apiKey: 'my-api-key',
+          customHeaders: {
+            'User-Agent': 'goff-web/3.0.0',
+            Authorization: 'Bearer foo',
+          },
         },
         logger,
       );
@@ -338,6 +342,7 @@ describe('GoFeatureFlagWebProvider', () => {
         const headers = lastCall[1]?.headers as never;
         expect(headers).not.toBeUndefined();
         expect(headers['Authorization']).toBe('Bearer my-api-key');
+        expect(headers['User-Agent']).toBe('goff-web/3.0.0');
         return;
       }
       expect(true).toBe(false);

@@ -44,6 +44,8 @@ export class GoFeatureFlagWebProvider implements Provider {
   private readonly _apiTimeout: number;
   // apiKey is the key used to identify your request in GO Feature Flag
   private readonly _apiKey: string | undefined;
+  // customHeaders to be sent for every HTTP request.
+  private readonly _customHeaders: Record<string, string> | undefined;
   // initial delay in millisecond to wait before retrying to connect
   private readonly _retryInitialDelay;
   // multiplier of _retryInitialDelay after each failure
@@ -68,6 +70,7 @@ export class GoFeatureFlagWebProvider implements Provider {
     this._retryDelayMultiplier = options.retryDelayMultiplier || 2;
     this._maxRetries = options.maxRetries || 10;
     this._apiKey = options.apiKey;
+    this._customHeaders = options.customHeaders;
     this._disableDataCollection = options.disableDataCollection || false;
 
     this._collectorManager = new CollectorManager(options, logger);
@@ -321,6 +324,7 @@ export class GoFeatureFlagWebProvider implements Provider {
         'Content-Type': 'application/json',
         Accept: 'application/json',
         // we had the authorization header only if we have an API Key
+        ...(this._customHeaders || {}),
         ...(this._apiKey ? { Authorization: `Bearer ${this._apiKey}` } : {}),
       },
       body: JSON.stringify(request),

@@ -45,6 +45,9 @@ export interface GoFeatureFlagWebProviderOptions {
   // Default: null
   apiKey?: string;
 
+  // customHeaders (optional) custom headers to be sent for every HTTP request.
+  customHeaders?: Record<string, string>;
+
   // initial delay in millisecond to wait before retrying to connect to GO Feature Flag (websocket and API)
   // Default: 100 ms
   retryInitialDelay?: number;