Does edge function location affect middleware as well?

[heecheon92]

Summary

I found I could set "Function Region" in vercel. Does this settings also affect the region of the Middleware?

Or is it independent?

Additional information

No response

Example

No response

[weyniis]

Hey, and one that's easy to overlook when working with Vercel Edge Functions and Middleware.

The short answer is:

Yes, setting the “Function Region” in Vercel does affect Middleware as well, because both Edge Functions and Middleware are executed on the Edge Network, and region placement impacts where that execution happens.

---

🧠 Here's the breakdown:

• In Vercel, Middleware runs on the Edge Runtime, same as Edge API routes.
• When u specify a region (e.g., lhr1, sfo1), it applies to both Edge Functions and Middleware deployed in your project.
• This ensures that latency is minimized for users close to that region, and it avoids cross-region cold starts or unnecessary delays.

---

📦 Example in vercel.json:

{
  "functions": {
    "middleware.ts": {
      "runtime": "edge",
      "regions": ["sfo1"]
    },
    "api/hello.ts": {
      "runtime": "edge",
      "regions": ["sfo1"]
    }
  }
}

In this config, both middleware.ts and api/hello.ts will execute in the sfo1 region, reducing latency for west coast users, for example.


 Notes:

If u don’t explicitly define a region, Vercel will run the edge function or middleware in the default nearest region to the incoming request.

If u define regions inconsistently across files, it might lead to cross-region calls and slightly higher latency.

 So to answer clearly: Yes, Edge Function location settings do affect Middleware if both are using the Edge Runtime. If u want them co-located (same latency, same region), set the region explicitly for both.

Let me know if u want a ready example setup for testing or deployment!