Fix Next.js 16 Warning: The 'middleware' file convention is deprecated. Please use 'proxy' instead
Migrate Next.js middleware.ts to the new proxy.ts convention introduced in Next.js 16 App Router.
⚠ The "middleware" file convention is deprecated. Please use "proxy" instead. To migrate automatically, run: npx @next/codemod@canary middleware-to-proxy .
# Run official Next.js 16 codemod: npx @next/codemod@canary middleware-to-proxy . # Or manually rename src/middleware.ts to src/proxy.ts and export function proxy(req: NextRequest)
Root Cause & Mechanism Analysis
Why does this error occur?
Next.js 16 renamed `middleware.ts` to `proxy.ts` (and the exported `middleware` function to `proxy`) to clarify that it runs as a network request boundary proxy rather than full Express-style application middleware.
Frequently Asked Questions
Does the matcher config syntax change in proxy.ts?
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