feat!: remove defaultUserAgent option with empty UA fallback

README.md

@@ -41,6 +41,8 @@ You can use the following flags to detect the device type:
 
 The user agent is also injected and accessible with `$device.userAgent`.
 
+If a request has no `User-Agent` header, `$device.userAgent` is an empty string and the device is treated as a desktop with an unknown OS and browser.
+
 The crawler detection is powered by the [crawler-user-agents](https://github.com/monperrus/crawler-user-agents) package.
 
 ## Usage
@@ -81,13 +83,11 @@ definePageMeta({
 </script>
 ```
 
-### Options
-
-#### `defaultUserAgent`
+## Static Generation
 
-Sets the default value for the `user-agent` header (useful when running `npm run generate`).
+Static generation (e.g. `nuxt generate`) is not supported. Prerendered pages are rendered once at build time without a user agent, so they are always rendered as a desktop.
 
-Default: `Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.39 Safari/537.36`
+To detect the device on each request, deploy with `nuxt build` instead. For a client-side only app, set `ssr: false` to detect the device in the browser.
 
 ## Amazon CloudFront Support
 

package.json

@@ -44,9 +44,6 @@
         "test": "vitest run",
         "test:watch": "vitest watch"
     },
-    "dependencies": {
-        "defu": "^6.1.7"
-    },
     "devDependencies": {
         "@nuxt/devtools": "latest",
         "@nuxt/eslint-config": "^1.17.0",

playground/nuxt.config.ts

@@ -5,5 +5,4 @@ export default defineNuxtConfig({
     compatibilityVersion: 5,
   },
   compatibilityDate: '2026-09-29',
-  device: {},
 })

src/module.ts

@@ -1,23 +1,16 @@
-import { defu } from 'defu'
 import { defineNuxtModule, addPlugin, addImportsDir, createResolver, addTemplate } from '@nuxt/kit'
 import crawlers from 'crawler-user-agents' with { type: 'json' }
 import { name, version } from '../package.json'
-import type { ModuleOptions } from './types'
 
-export default defineNuxtModule<ModuleOptions>({
+export default defineNuxtModule({
   meta: {
     name,
-    configKey: 'device',
     compatibility: {
       nuxt: '>=4.0.0',
     },
     version,
   },
-  setup(options, nuxt) {
-    nuxt.options.runtimeConfig.public.device = defu(nuxt.options.runtimeConfig.public.device, {
-      defaultUserAgent: 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.39 Safari/537.36',
-    })
-
+  setup() {
     const { resolve } = createResolver(import.meta.url)
 
     addPlugin(resolve('./runtime/plugin'))

src/runtime/plugin.ts

@@ -1,26 +1,18 @@
 import type { Plugin } from 'nuxt/app'
 import type { Device } from './types'
 import generateFlags from './generateFlags'
-import { defineNuxtPlugin, reactive, useRequestHeaders, useRuntimeConfig } from '#imports'
+import { defineNuxtPlugin, reactive, useRequestHeaders } from '#imports'
 
 const plugin: Plugin<{ device: Device }> = defineNuxtPlugin(() => {
-  const runtimeConfig = useRuntimeConfig()
-
-  const defaultUserAgent = runtimeConfig.public.device.defaultUserAgent
-
   let flags: Device
 
   if (import.meta.server) {
     const headers = useRequestHeaders()
 
-    const userAgent = headers['user-agent'] || defaultUserAgent
-
-    flags = reactive(generateFlags(userAgent, headers))
+    flags = reactive(generateFlags(headers['user-agent'] || '', headers))
   }
   else {
-    const userAgent = navigator.userAgent || defaultUserAgent
-
-    flags = reactive(generateFlags(userAgent))
+    flags = reactive(generateFlags(navigator.userAgent))
   }
 
   return {

test/basic.test.ts

@@ -61,6 +61,16 @@ describe('ssr', async () => {
     expect(html).toContain('isCrawler')
   })
 
+  it('treats an empty user agent as a desktop', async () => {
+    const html = await $fetch('/', {
+      headers: {
+        'User-Agent': '',
+      },
+    })
+
+    expect(parseHtml(html)).toEqual({ isDesktop: true, isMobile: false, isTablet: false, isMobileOrTablet: false, isDesktopOrTablet: true, isIos: false, isWindows: false, isMacOS: false, isLinux: false, isApple: false, isAndroid: false, isFirefox: false, isEdge: false, isChrome: false, isSafari: false, isSamsung: false, isCrawler: false })
+  })
+
   describe('detects device', () => {
     it('Samsung Galaxy S9', async () => {
       const userAgent = 'Mozilla/5.0 (Linux; Android 8.0.0; SM-G960F Build/R16NW) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.84 Mobile Safari/537.36'