diff --git a/src/api/auth.ts b/src/api/auth.ts
index c6f44be..d9389be 100644
--- a/src/api/auth.ts
+++ b/src/api/auth.ts
@@ -13,7 +13,7 @@ import type {
   VerifyEmailRequest,
   VerifyEmailResponse,
 } from "@/api/types";
-import { AUTH_ENDPOINTS } from "@/lib/constants";
+import { AUTH_ENDPOINTS, CLIENT_HEADER, CLIENT_HEADER_VALUE } from "@/lib/constants";
 import { accessTokenStorage, refreshTokenStorage } from "@/lib/storage";
 import {
   loginResponseSchema,
@@ -99,7 +99,7 @@ export async function refreshAccessToken(): Promise<boolean> {
   try {
     const res = await fetch(AUTH_ENDPOINTS.deviceRefresh, {
       method: "POST",
-      headers: { "Content-Type": "application/json" },
+      headers: { "Content-Type": "application/json", [CLIENT_HEADER]: CLIENT_HEADER_VALUE },
       body: JSON.stringify({ refresh_token: refreshToken }),
       signal: AbortSignal.timeout(10_000),
     });
diff --git a/src/api/client.ts b/src/api/client.ts
index ee3f9c8..f1af3f3 100644
--- a/src/api/client.ts
+++ b/src/api/client.ts
@@ -1,5 +1,5 @@
 import type { ApiErrorResponse } from "@/api/types";
-import { AUTH_ENDPOINTS } from "@/lib/constants";
+import { AUTH_ENDPOINTS, CLIENT_HEADER, CLIENT_HEADER_VALUE } from "@/lib/constants";
 import { ApiError, isOffline, NetworkError } from "@/lib/errors";
 import {
   accessTokenStorage,
@@ -43,7 +43,7 @@ async function refreshAccessToken(): Promise<string | null> {
   try {
     const res = await fetch(AUTH_ENDPOINTS.deviceRefresh, {
       method: "POST",
-      headers: { "Content-Type": "application/json" },
+      headers: { "Content-Type": "application/json", [CLIENT_HEADER]: CLIENT_HEADER_VALUE },
       body: JSON.stringify({ refresh_token: refreshToken }),
     });
 
@@ -88,6 +88,9 @@ export async function request<T>(
     }
   }
 
+  // Client attribution header (all request() URLs point at the spoo.me backend)
+  headers[CLIENT_HEADER] = CLIENT_HEADER_VALUE;
+
   // Auth header
   if (!noAuth) {
     const authHeader = await getAuthHeader();
diff --git a/src/api/export.ts b/src/api/export.ts
index c8e835d..3c4d1a6 100644
--- a/src/api/export.ts
+++ b/src/api/export.ts
@@ -1,5 +1,5 @@
 import type { ExportQuery } from "@/api/types";
-import { API_V1 } from "@/lib/constants";
+import { API_V1, CLIENT_HEADER, CLIENT_HEADER_VALUE } from "@/lib/constants";
 import { isOffline, NetworkError } from "@/lib/errors";
 import { accessTokenStorage, apiKeyStorage, authModeStorage } from "@/lib/storage";
 
@@ -17,7 +17,7 @@ export async function exportStats(query: ExportQuery): Promise<Blob> {
     }
   }
 
-  const headers: Record<string, string> = {};
+  const headers: Record<string, string> = { [CLIENT_HEADER]: CLIENT_HEADER_VALUE };
   const mode = await authModeStorage.getValue();
   if (mode === "apikey") {
     const key = await apiKeyStorage.getValue();
diff --git a/src/api/stats.ts b/src/api/stats.ts
index 981db43..cef117d 100644
--- a/src/api/stats.ts
+++ b/src/api/stats.ts
@@ -1,6 +1,6 @@
 import { request } from "@/api/client";
 import type { StatsQuery, StatsResponse } from "@/api/types";
-import { API_BASE_URL, API_V1 } from "@/lib/constants";
+import { API_BASE_URL, API_V1, CLIENT_HEADER, CLIENT_HEADER_VALUE } from "@/lib/constants";
 import { ApiError } from "@/lib/errors";
 import { statsResponseSchema } from "@/schemas/api";
 
@@ -50,7 +50,7 @@ export interface V0StatsResponse {
  */
 export async function getStatsV0(shortCode: string, password?: string): Promise<V0StatsResponse> {
   const url = `${API_BASE_URL}/stats/${shortCode}`;
-  const headers: Record<string, string> = {};
+  const headers: Record<string, string> = { [CLIENT_HEADER]: CLIENT_HEADER_VALUE };
 
   const body = password ? new URLSearchParams({ password }) : undefined;
   if (body) {
diff --git a/src/entrypoints/background/index.ts b/src/entrypoints/background/index.ts
index d20b4a7..48fcb22 100644
--- a/src/entrypoints/background/index.ts
+++ b/src/entrypoints/background/index.ts
@@ -5,6 +5,8 @@ import {
   ACCESS_TOKEN_TTL_MS,
   API_BASE_URL,
   AUTH_ENDPOINTS,
+  CLIENT_HEADER,
+  CLIENT_HEADER_VALUE,
   HISTORY_MAX_ITEMS,
   QR_BRAND,
   TOKEN_REFRESH_BUFFER_MS,
@@ -139,7 +141,7 @@ async function handleTokenRefresh(): Promise<void> {
 async function exchangeDeviceCode(code: string): Promise<void> {
   const res = await fetch(AUTH_ENDPOINTS.deviceToken, {
     method: "POST",
-    headers: { "Content-Type": "application/json" },
+    headers: { "Content-Type": "application/json", [CLIENT_HEADER]: CLIENT_HEADER_VALUE },
     body: JSON.stringify({ code }),
   });
 
diff --git a/src/lib/constants.ts b/src/lib/constants.ts
index 9e45ad0..d29517e 100644
--- a/src/lib/constants.ts
+++ b/src/lib/constants.ts
@@ -4,6 +4,10 @@ export const QR_API_BASE_URL = import.meta.env.VITE_QR_API_BASE_URL || "https://
 export const API_V1 = `${API_BASE_URL}/api/v1`;
 export const QR_API_V1 = `${QR_API_BASE_URL}/api/v1`;
 
+/** Identifies this client to the spoo.me API. Never sent to third-party hosts. */
+export const CLIENT_HEADER = "X-Spoo-Client";
+export const CLIENT_HEADER_VALUE = `snap/${browser.runtime.getManifest().version}`;
+
 export const AUTH_ENDPOINTS = {
   login: `${API_BASE_URL}/auth/login`,
   register: `${API_BASE_URL}/auth/register`,