diff --git a/docs/typedoc.js b/docs/typedoc.js
deleted file mode 100644
index 254c9ee..0000000
--- a/docs/typedoc.js
+++ /dev/null
@@ -1,12 +0,0 @@
-module.exports = {
-  out: './docs/build/html',
-  exclude: [
-    '**/node_modules/**',
-    'test-types.ts'
-  ],
-  name: "LaunchDarkly Javascript SDK Core Components (3.3.4)",
-  readme: 'none',                // don't add a home page with a copy of README.md
-  mode: 'file',                  // don't treat "index.d.ts" itself as a parent module
-  includeDeclarations: true,     // allows it to process a .d.ts file instead of actual TS code
-  entryPoint: '"launchdarkly-js-sdk-common"'  // note extra quotes - workaround for a TypeDoc bug
-};
diff --git a/src/EventSender.js b/src/EventSender.js
index 6a0a2e3..a1cfb7e 100644
--- a/src/EventSender.js
+++ b/src/EventSender.js
@@ -34,7 +34,7 @@ export default function EventSender(platform, environmentId, options) {
             'X-LaunchDarkly-Payload-ID': payloadId,
           });
       return platform
-        .httpRequest('POST', url, headers, jsonBody)
+        .httpRequest('POST', url, utils.transformHeaders(headers, options), jsonBody)
         .promise.then(result => {
           if (!result) {
             // This was a response from a fire-and-forget request, so we won't have a status.
diff --git a/src/Requestor.js b/src/Requestor.js
index f692906..f4db4be 100644
--- a/src/Requestor.js
+++ b/src/Requestor.js
@@ -45,7 +45,7 @@ export default function Requestor(platform, options, environment) {
       activeRequests[endpoint] = coalescer;
     }
 
-    const req = platform.httpRequest(method, endpoint, headers, body);
+    const req = platform.httpRequest(method, endpoint, utils.transformHeaders(headers, options), body);
     const p = req.promise.then(
       result => {
         if (result.status === 200) {
diff --git a/src/Stream.js b/src/Stream.js
index 70a9862..9f7b727 100644
--- a/src/Stream.js
+++ b/src/Stream.js
@@ -1,5 +1,5 @@
 import * as messages from './messages';
-import { base64URLEncode, getLDHeaders, objectHasOwnProperty } from './utils';
+import { base64URLEncode, getLDHeaders, transformHeaders, objectHasOwnProperty } from './utils';
 
 // The underlying event source implementation is abstracted via the platform object, which should
 // have these three properties:
@@ -104,6 +104,7 @@ export default function Stream(platform, config, environment, diagnosticsAccumul
       } else {
         url = evalUrlPrefix + '/' + base64URLEncode(JSON.stringify(user));
       }
+      options.headers = transformHeaders(options.headers, config);
       if (withReasons) {
         query = query + (query ? '&' : '') + 'withReasons=true';
       }
diff --git a/src/__tests__/EventSender-test.js b/src/__tests__/EventSender-test.js
index fe9ab35..9bda1f4 100644
--- a/src/__tests__/EventSender-test.js
+++ b/src/__tests__/EventSender-test.js
@@ -149,6 +149,23 @@ describe('EventSender', () => {
       expect(r.headers['x-launchdarkly-wrapper']).toEqual('FakeSDK');
     });
 
+    it('should send transformed headers if requestHeaderTransform function is provided', async () => {
+      const headerTransform = input => {
+        const output = { ...input };
+        output['c'] = '30';
+        return output;
+      };
+      const options = { requestHeaderTransform: headerTransform };
+      const server = platform.testing.http.newServer();
+      server.byDefault(respond(202));
+      const sender = EventSender(platform, envId, options);
+      const event = { kind: 'identify', key: 'userKey' };
+      await sender.sendEvents([event], server.url);
+
+      const r = await server.nextRequest();
+      expect(r.headers['c']).toEqual('30');
+    });
+
     describe('retry on recoverable HTTP error', () => {
       const retryableStatuses = [400, 408, 429, 500, 503];
       for (const i in retryableStatuses) {
diff --git a/src/__tests__/Requestor-test.js b/src/__tests__/Requestor-test.js
index e9c6db1..474515d 100644
--- a/src/__tests__/Requestor-test.js
+++ b/src/__tests__/Requestor-test.js
@@ -227,6 +227,24 @@ describe('Requestor', () => {
     });
   });
 
+  it('sends transformed headers if requestHeaderTransform function is provided', async () => {
+    await withServer(async (baseConfig, server) => {
+      const headerTransform = input => {
+        const output = { ...input };
+        output['b'] = '20';
+        return output;
+      };
+      const config = { ...baseConfig, requestHeaderTransform: headerTransform };
+      const requestor = Requestor(platform, config, env);
+
+      await requestor.fetchFlagSettings(user);
+
+      expect(server.requests.length()).toEqual(1);
+      const req = await server.requests.take();
+      expect(req.headers['b']).toEqual('20');
+    });
+  });
+
   it('returns parsed JSON response on success', async () => {
     const data = { foo: 'bar' };
     await withServer(async (baseConfig, server) => {
diff --git a/src/__tests__/Stream-test.js b/src/__tests__/Stream-test.js
index fa8a6c7..a392d7b 100644
--- a/src/__tests__/Stream-test.js
+++ b/src/__tests__/Stream-test.js
@@ -120,6 +120,20 @@ describe('Stream', () => {
     expect(created.options.headers).toEqual({});
   });
 
+  it('sends transformed headers if requestHeaderTransform function is provided', async () => {
+    const headerTransform = input => {
+      const output = { ...input };
+      output['a'] = '10';
+      return output;
+    };
+    const config = { ...defaultConfig, requestHeaderTransform: headerTransform };
+    const stream = new Stream(platform, config, envName);
+    stream.connect(user, null, {});
+
+    const created = await platform.testing.expectStream(makeExpectedStreamUrl(encodedUser));
+    expect(created.options.headers).toEqual({ ...baseHeaders, a: '10' });
+  });
+
   it('sets event listeners', async () => {
     const stream = new Stream(platform, defaultConfig, envName);
     const fn1 = jest.fn();
diff --git a/src/__tests__/utils-test.js b/src/__tests__/utils-test.js
index f47f980..0f95b9b 100644
--- a/src/__tests__/utils-test.js
+++ b/src/__tests__/utils-test.js
@@ -1,6 +1,7 @@
 import {
   base64URLEncode,
   getLDHeaders,
+  transformHeaders,
   getLDUserAgentString,
   wrapPromiseCallback,
   chunkUserEventsForUrl,
@@ -79,6 +80,38 @@ describe('utils', () => {
     });
   });
 
+  describe('transformHeaders', () => {
+    it('does not modify the headers if the option is not available', () => {
+      const inputHeaders = { a: '1', b: '2' };
+      const headers = transformHeaders(inputHeaders, {});
+      expect(headers).toEqual(inputHeaders);
+    });
+
+    it('modifies the headers if the option has a transform', () => {
+      const inputHeaders = { c: '3', d: '4' };
+      const outputHeaders = { c: '9', d: '4', e: '5' };
+      const headerTransform = input => {
+        const output = { ...input };
+        output['c'] = '9';
+        output['e'] = '5';
+        return output;
+      };
+      const headers = transformHeaders(inputHeaders, { requestHeaderTransform: headerTransform });
+      expect(headers).toEqual(outputHeaders);
+    });
+
+    it('cannot mutate the input header object', () => {
+      const inputHeaders = { f: '6' };
+      const expectedInputHeaders = { f: '6' };
+      const headerMutate = input => {
+        input['f'] = '7'; // eslint-disable-line no-param-reassign
+        return input;
+      };
+      transformHeaders(inputHeaders, { requestHeaderTransform: headerMutate });
+      expect(inputHeaders).toEqual(expectedInputHeaders);
+    });
+  });
+
   describe('getLDUserAgentString', () => {
     it('uses platform user-agent and package version by default', () => {
       const platform = stubPlatform.defaults();
diff --git a/src/configuration.js b/src/configuration.js
index c595ce6..d779f10 100644
--- a/src/configuration.js
+++ b/src/configuration.js
@@ -18,6 +18,7 @@ export const baseOptionDefs = {
   sendEvents: { default: true },
   streaming: { type: 'boolean' }, // default for this is undefined, which is different from false
   sendLDHeaders: { default: true },
+  requestHeaderTransform: { type: 'function' },
   inlineUsersInEvents: { default: false },
   allowFrequentDuplicateEvents: { default: false },
   sendEventsOnlyForVariation: { default: false },
diff --git a/src/utils.js b/src/utils.js
index 37f6b1a..ad9a40c 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -165,6 +165,13 @@ export function getLDHeaders(platform, options) {
   return h;
 }
 
+export function transformHeaders(headers, options) {
+  if (!options || !options.requestHeaderTransform) {
+    return headers;
+  }
+  return options.requestHeaderTransform({ ...headers });
+}
+
 export function extend(...objects) {
   return objects.reduce((acc, obj) => ({ ...acc, ...obj }), {});
 }
diff --git a/test-types.ts b/test-types.ts
index bf63737..9c5bac5 100644
--- a/test-types.ts
+++ b/test-types.ts
@@ -39,6 +39,7 @@ var allBaseOptions: ld.LDOptionsBase = {
   streaming: true,
   useReport: true,
   sendLDHeaders: true,
+  requestHeaderTransform: (x) => x,
   evaluationReasons: true,
   sendEvents: true,
   allAttributesPrivate: true,
diff --git a/typings.d.ts b/typings.d.ts
index 731d283..812d3b5 100644
--- a/typings.d.ts
+++ b/typings.d.ts
@@ -139,6 +139,14 @@ declare module 'launchdarkly-js-sdk-common' {
      */
     sendLDHeaders?: boolean;
 
+    /**
+     * A transform function for dynamic configuration of HTTP headers.
+     *
+     * This method will run last in the header generation sequence, so the function should have
+     * all system generated headers in case those also need to be modified.
+     */
+    requestHeaderTransform?: (headers: Map<string, string>) => Map<string, string>;
+
     /**
      * Whether LaunchDarkly should provide additional information about how flag values were
      * calculated.