http: superfluous response.WriteHeader call Go Origin: Application & API Last updated 4 Nov 2026

Go: http: superfluous response.WriteHeader call from main.handler (main.go:25)

A handler wrote the status header more than once, or wrote the body first (which sends 200) and then tried to set another status.

Exact message you may see http: superfluous response.WriteHeader callhttp: superfluous response.WriteHeader call from main.handlersuperfluous response.WriteHeader call from
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Seen on: Go

Meaning

The first Write implicitly sends status 200. Calling WriteHeader or http.Error afterwards is ignored and logged. Return after sending an error, and set status/headers before writing the body.

Common causes

  • http.Error followed by more writes
  • Missing return after writing an error response
  • WriteHeader called after Write
  • Middleware and handler both writing
  • Calling WriteHeader twice

⚡ Quick fix

  1. return immediately after http.Error(...)
  2. Call w.WriteHeader(code) before any w.Write
  3. Avoid writing from middleware after the handler

Detailed fix by platform

Go

  1. if err != nil { http.Error(w, err.Error(), 500); return }

How to diagnose

  1. Order — Header before body?
  2. Return — After errors?
  3. Writers — Multiple layers?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Application & API. Errors that are often confused with or caused by this one (click to open):

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