diff --git a/README.md b/README.md
index af5ea08..5b06129 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,9 @@ async function someBrokerizeActions() {
     createWebSocket: (url, protocol) => new WebSocket(url, protocol),
     // basePath: 'https://api-preview.brokerize.com', // this is the default value
     // basePathCryptoService: 'https://crypto-service-api.com' // the optional external crypto service
+    // acceptLanguage: 'de', // optional `Accept-Language` header for localized responses (e.g. legal terms).
+    //                       // may also be a function `() => 'de'` that is evaluated on every request,
+    //                       // so runtime language changes are picked up without recreating the client.
   })
 
   /* create a guest user. the result contains the user's tokens and be stored, e.g. in a cookie or session storage */
diff --git a/src/apiCtx.ts b/src/apiCtx.ts
index 457b0ae..603925e 100644
--- a/src/apiCtx.ts
+++ b/src/apiCtx.ts
@@ -22,6 +22,50 @@ export interface BrokerizeConfig {
    * The AWS cognito configuration, if the application is supposed to be used with brokerize accounts.
    */
   cognito?: CognitoConfig;
+  /**
+   * Optional value for the `Accept-Language` header sent with API requests. Use this to request
+   * localized backend responses (e.g. legal terms) in the language selected in your application,
+   * overriding the language the browser would send by default.
+   *
+   * Accepts a static value (e.g. `"de"`, `"en"`, `"de-DE"`) or a function that returns the current
+   * language. The function is evaluated on every request, so runtime language changes are picked up
+   * without recreating the client. Return `undefined`/`null` (or provide no value) to omit the
+   * header and let the runtime/browser default apply.
+   */
+  acceptLanguage?:
+    | string
+    | (() => string | null | undefined | Promise<string | null | undefined>);
+}
+
+/**
+ * Resolves the configured `Accept-Language` value (static or via a getter function) to a string,
+ * or `undefined` if none is configured / the getter yields an empty value.
+ */
+export async function resolveAcceptLanguage(
+  cfg: BrokerizeConfig,
+): Promise<string | undefined> {
+  const { acceptLanguage } = cfg;
+  const value =
+    typeof acceptLanguage === "function"
+      ? await acceptLanguage()
+      : acceptLanguage;
+  return value || undefined;
+}
+
+/**
+ * Adds the configured `Accept-Language` header to the given headers object (mutating and returning
+ * it) if a language is configured. No-op otherwise. Used to apply the configured language uniformly
+ * to authorized and unauthenticated requests.
+ */
+export async function withAcceptLanguage(
+  cfg: BrokerizeConfig,
+  headers: Record<string, string>,
+): Promise<Record<string, string>> {
+  const acceptLanguage = await resolveAcceptLanguage(cfg);
+  if (acceptLanguage) {
+    headers["Accept-Language"] = acceptLanguage;
+  }
+  return headers;
 }
 
 export type AuthContextConfiguration =
@@ -102,10 +146,10 @@ export function createAuth({
             }
             const response = await fetch(cfg.basePath + "/user/token", {
               method: "POST",
-              headers: {
+              headers: await withAcceptLanguage(cfg, {
                 "x-brkrz-client-id": cfg.clientId,
                 "Content-Type": "application/x-www-form-urlencoded",
-              },
+              }),
               // XXX some runtimes do not have URLSearchParams, so just produce the body in the old-fashioned way
               body: `grant_type=refresh_token&refresh_token=${encodeURIComponent(
                 guestAuthCfg.tokens.response.refreshToken,
diff --git a/src/authorizedApiContext.ts b/src/authorizedApiContext.ts
index eb27e22..b9b49df 100644
--- a/src/authorizedApiContext.ts
+++ b/src/authorizedApiContext.ts
@@ -1,5 +1,10 @@
 import { Subject } from "rxjs";
-import { Auth, BrokerizeConfig, createConfiguration } from "./apiCtx";
+import {
+  Auth,
+  BrokerizeConfig,
+  createConfiguration,
+  withAcceptLanguage,
+} from "./apiCtx";
 import { BrokerizeError } from "./errors";
 import { createPollingSubscription } from "./pollingSubscription";
 import * as openApiClient from "./swagger";
@@ -171,13 +176,14 @@ export class AuthorizedApiContext {
       throw new Error("AuthorizedApiContext is destroyed");
     }
     const tok = await this._auth.getToken();
+    const headers = await withAcceptLanguage(this._cfg, {
+      "x-brkrz-client-id": this._cfg.clientId,
+      Authorization: "Bearer " + tok.idToken,
+      "Content-Type": "application/json",
+    });
     return {
       signal: this._abortController.signal,
-      headers: {
-        "x-brkrz-client-id": this._cfg.clientId,
-        Authorization: "Bearer " + tok.idToken,
-        "Content-Type": "application/json",
-      },
+      headers,
     };
   }
   async getBrokers() {
diff --git a/src/index.ts b/src/index.ts
index 29c35f2..00c61a7 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -12,6 +12,7 @@ import {
   GuestAuthContextConfiguration,
   RegisteredUserAuthContextConfiguration,
   TokenSet,
+  withAcceptLanguage,
 } from "./apiCtx";
 import {
   AuthorizedApiContext,
@@ -108,10 +109,10 @@ export class Brokerize {
   ): Promise<GuestAuthContextConfiguration> {
     const response = await fetch(this._cfg.basePath + "/user/token", {
       method: "POST",
-      headers: {
+      headers: await withAcceptLanguage(this._cfg, {
         "x-brkrz-client-id": this._cfg.clientId,
         "Content-Type": "application/x-www-form-urlencoded",
-      },
+      }),
       // XXX some runtimes do not have URLSearchParams, so just produce the body in the old-fashioned way
       body: `grant_type=refresh_token&refresh_token=${encodeURIComponent(
         refreshToken,
@@ -159,10 +160,10 @@ export class Brokerize {
   async createGuestUser(): Promise<AuthContextConfiguration> {
     const updatedAt = Date.now();
     const user = await this._userApi.createGuestUser({
-      headers: {
+      headers: await withAcceptLanguage(this._cfg, {
         "x-brkrz-client-id": this._cfg.clientId,
         "Content-Type": "application/json",
-      },
+      }),
     });
     return {
       type: "guest",
@@ -218,16 +219,16 @@ export class Brokerize {
     });
   }
 
-  checkRecoveryPhrase(recoveryPhrase: string) {
+  async checkRecoveryPhrase(recoveryPhrase: string) {
     return this._userApi.checkRecoveryPhrase(
       {
         obtainTokenByRecoveryPhraseParams: { recoveryPhrase },
       },
       {
-        headers: {
+        headers: await withAcceptLanguage(this._cfg, {
           "x-brkrz-client-id": this._cfg.clientId,
           "Content-Type": "application/json",
-        },
+        }),
       },
     );
   }
@@ -240,10 +241,10 @@ export class Brokerize {
         obtainTokenByRecoveryPhraseParams: { recoveryPhrase },
       },
       {
-        headers: {
+        headers: await withAcceptLanguage(this._cfg, {
           "x-brkrz-client-id": this._cfg.clientId,
           "Content-Type": "application/json",
-        },
+        }),
       },
     );