HTTP 303 See Other

What It Means

The HTTP 303 See Other status code indicates that the response to the request can be found at a different URI. The client should use GET to retrieve the resource at the new location, regardless of the original request method.

The PRG Pattern

303 is essential for the Post/Redirect/Get (PRG) pattern, which prevents duplicate form submissions:

# 1. User submits form
POST /orders HTTP/1.1
Content-Type: application/x-www-form-urlencoded

product=widget&quantity=5

# 2. Server creates order and redirects
HTTP/1.1 303 See Other
Location: /orders/12345

# 3. Browser follows redirect with GET
GET /orders/12345 HTTP/1.1

# 4. User sees confirmation page
HTTP/1.1 200 OK
Content-Type: text/html

<h1>Order #12345 confirmed!</h1>

Why PRG Matters

• Prevents double-submit: Refreshing the page won't resubmit the form
• Clean URLs: User's address bar shows the result page, not the action
• Bookmarkable: The confirmation page can be bookmarked
• Back button works: No "resubmit form?" warnings

303 vs Other Redirects

*302 behavior varies by browser, 303 is explicit

Key Difference from 307

303 explicitly changes the method to GET, while 307 preserves the original method. Use 303 when redirecting after a POST to show a result page; use 307 when temporarily moving an API endpoint that should keep the same method.