Why Next.js 16 Swapped middleware.ts for proxy.ts – What You Need to Know

Next.js 16 introduced a subtle yet significant change: the file formerly known as middleware.ts is now called proxy.ts. While the rename may look cosmetic, it reflects deeper considerations about clarity, security, and architectural intent.

proxy.ts is defined as the edge‑runtime file that houses the function previously exported as middleware in Next.js 16.

Why the Rename Matters

The Next.js team renamed the file to avoid confusion with Express.js middleware, a pattern many developers mistakenly associate with the edge function (Source: Renaming Middleware to Proxy – Next.js). By using the term “proxy,” the framework signals that this file is intended for request‑level routing and transformation rather than generic server‑side logic.

What proxy.ts Does in Practice

Despite the new name, the exported function still works exactly as before: it receives a NextRequest and returns a NextResponse. The core responsibilities typically include:

• Authentication checks and token validation.
• Geolocation‑based redirects or rewrites.
• Header manipulation for caching or security policies.
• Custom logging or analytics hooks.

Developers often bundle unrelated logic into a single proxy.ts file, as seen in many real‑world projects where the file grows to 200+ lines handling multiple concerns.

Managing Multiple Responsibilities in a Single File

Having four unrelated jobs in one file is rarely accidental. It reflects a pragmatic approach where teams prioritize speed over strict separation. However, this can lead to maintenance challenges. To keep the codebase clean:

1. Separate concerns: Extract authentication logic into a dedicated helper module.
2. Use composable middlewares: Create small functions that each handle a single task and compose them in proxy.ts.
3. Leverage TypeScript: Define clear interfaces for request and response transformations.

Best Practices for Migrating to proxy.ts

When moving from middleware.ts to proxy.ts, follow the simple three‑step codemod process described by konadu.dev:

• Rename the file (e.g., mv middleware.ts proxy.ts).
• Rename the exported function from middleware to proxy if desired, though keeping the name middleware is acceptable for readability.
• Ensure the file exports a single function that handles the request and returns a response.

These steps guarantee that your application continues to work with Next.js 16’s edge runtime without unexpected breakages (Source: Next.js 16 Renamed middleware.ts to proxy.ts – konadu.dev).

Frequently Asked Questions

Is renaming to proxy.ts mandatory for all Next.js projects?

Yes. Starting with Next.js 16, the framework expects the edge function file to be named proxy.ts (or proxy.js) at the project root or within src/. The old name is deprecated and will trigger warnings.

Can I keep the exported function named middleware?

Absolutely. The function name is independent of the file name. Many developers retain middleware for readability, as the term still accurately describes its purpose.

What security benefits does the rename provide?

By clarifying the intent, the rename reduces the risk of developers misusing the edge function for heavy server‑side logic, which could expose the application to performance bottlenecks and potential attack vectors (Source: Renaming Middleware to Proxy – Next.js).

Do I need to update my CI/CD pipelines after the rename?

Only if your pipelines reference the file path directly. Update any scripts that copy, lint, or deploy middleware.ts to point to proxy.ts.

Will existing middleware logic continue to work after migration?

Yes. The API surface—NextRequest, NextResponse, and the matcher configuration—remains unchanged, so your logic will function as before.

Neptune Infotech can help you smoothly transition to Next.js 16 and optimize your edge functions for performance and security.