303 🌐 HTTP

HTTP 303 See Other

A redirect telling the client to fetch the result from another URL with GET — used after a form POST so refreshing doesn’t resubmit.

Seen on: REST API

Meaning

303 is the correct response for Post/Redirect/Get: the server handled the POST, then points the browser at a results page. Unlike 301/302, 303 always switches the follow-up request to GET.

Issues arise when an API client expects JSON from the POST but receives a 303 (and silently follows it), or when a redirect target loops back.

Common causes

  • Server implements Post/Redirect/Get after a form submission
  • Framework redirect helper uses 303 for non-GET requests (Rails, FastAPI RedirectResponse)
  • API client following redirects automatically and losing the POST response

⚡ Quick fix

  1. For browser forms, this is correct behaviour
  2. For APIs, return 200/201 with a body instead of redirecting
  3. Disable automatic redirect following to inspect the response

Detailed fix by platform

curl

  1. curl -i -X POST https://example.com/orders -d 'qty=1' # see the 303 and its Location

Python

  1. requests.post(url, data=d, allow_redirects=False) # inspect r.status_code / r.headers['Location']

How to diagnose

  1. Location — Where does it point?
  2. Method — Was a POST turned into GET?
  3. Loop — Does the target redirect again?

🔧 Still not fixed?

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