Vercel Middleware

How it works

Vercel runs a middleware file for every request your site serves. ByDefault's middleware reports the requests that come from AI tools asynchronously, so there is no performance impact.

It works on any Vercel plan and any framework, static and client-rendered sites included.

Set up the middleware

In ByDefault, open Analytics, click Connect your site, then pick Vercel and Middleware. Keep it open: it has your token and tells you when the middleware works.

1. Install the package in the project that serves your site.

   npm install @bydefault/vercel

   With another package manager, run pnpm add, yarn add or bun add @bydefault/vercel.

2. Create the middleware file at the project root. On Next.js, put it inside src/ if your project uses one. The file's name depends on your framework:

   Framework	File
   Next.js 16 or newer	proxy.ts
   Next.js 15 or older	middleware.ts
   Anything else	middleware.ts, next to package.json

   On Next.js 16 or newer:

   proxy.ts

   import { Tracker } from '@bydefault/vercel'
   
   const tracker = new Tracker({
     token: process.env.BYDEFAULT_TOKEN,
   })
   
   export default function proxy(request: Request) {
     // No await needed: this automatically runs non-blocking,
     // after the response has been sent.
     tracker.track(request)
   }
   
   export const config = {
     // Run on all paths except static assets
     matcher: '/((?!_next/static|_next/image|favicon.ico).*)',
   }

   On Next.js 15 or older, use the same code in middleware.ts and name the function middleware. On any other framework, leave out config:

   middleware.ts

   import { Tracker } from '@bydefault/vercel'
   
   const tracker = new Tracker({
     token: process.env.BYDEFAULT_TOKEN,
   })
   
   export default function middleware(request: Request) {
     // No await needed: this automatically runs non-blocking,
     // after the response has been sent.
     tracker.track(request)
   }

3. Add your token to .env.local, and under Settings → Environment Variables on your Vercel project, so the deployed site has it too. The setup shows the line with your token in it.

   .env.local

   BYDEFAULT_TOKEN=bd_…

4. Push to GitHub, or run vercel deploy --prod.

Check the connection

While the setup is open, ByDefault visits your site the way an AI assistant would, every few seconds. When the deployed middleware first reports, the last step reads Your middleware reached us. Once it reports our visit, the step turns green.

Troubleshooting