diff --git a/.gitignore b/.gitignore
index e4ed3d2b..21bd24e5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,5 @@ node_modules
 npm-debug.log
 
 package-lock.json
+
+/id.json
diff --git a/lib/generate-install-id.js b/lib/generate-install-id.js
new file mode 100755
index 00000000..14235608
--- /dev/null
+++ b/lib/generate-install-id.js
@@ -0,0 +1,6 @@
+#!/usr/bin/env node
+
+const {randomBytes} = require('crypto')
+
+const id = randomBytes(6).toString('hex')
+process.stdout.write(JSON.stringify(id) + '\n')
diff --git a/lib/request.js b/lib/request.js
index 00396906..2567f082 100644
--- a/lib/request.js
+++ b/lib/request.js
@@ -1,5 +1,6 @@
 'use strict'
 
+const {join} = require('path')
 const createHash = require('create-hash')
 let captureStackTrace = () => {}
 if (process.env.NODE_DEBUG === 'hafas-client') {
@@ -9,6 +10,15 @@ const {stringify} = require('query-string')
 const Promise = require('pinkie-promise')
 const {fetch} = require('fetch-ponyfill')({Promise})
 
+let id
+try {
+	id = require('../id.json')
+} catch (err) {
+	const p = join(__dirname, '..', 'id.json')
+	console.error(`Failed to load the install-unique ID from ${p}.`)
+	process.exit(1)
+}
+
 const md5 = input => createHash('md5').update(input).digest()
 
 const request = (profile, userAgent, opt, data) => {
@@ -24,7 +34,7 @@ const request = (profile, userAgent, opt, data) => {
 			'Content-Type': 'application/json',
 			'Accept-Encoding': 'gzip, deflate',
 			'Accept': 'application/json',
-			'user-agent': userAgent
+			'user-agent': id + ' ' + userAgent
 		},
 		query: {}
 	})
diff --git a/package.json b/package.json
index 49e0c460..83ec9439 100644
--- a/package.json
+++ b/package.json
@@ -62,6 +62,7 @@
 	},
 	"scripts": {
 		"test": "env NODE_ENV=dev NODE_DEBUG=hafas-client node test/index.js",
-		"prepublishOnly": "npm test | tap-spec"
+		"prepublishOnly": "npm test | tap-spec",
+		"install": "lib/generate-install-id.js >id.json"
 	}
 }