303 See Other

Redirection: the client has to take another step, usually following a Location header, to complete the request.

When a server should send it. After a POST, to send the browser to a page showing the result. This is the Post/Redirect/Get pattern: refreshing the result page then repeats a harmless GET instead of resubmitting the form.

Common causes. The standard reply after a form POST, so refreshing the next page does not resubmit the form.

What to do. Follow the Location header with a GET.

Browsers and HTTP clients. Clients always follow it with GET (or HEAD), whatever the original method was, and the redirect itself is not cached.

Google Search. Treated like 302: a weak signal that the redirect target should be canonical. Source: Google Search Central, How HTTP status codes, and network and DNS errors affect Google Search.

Caching. Not cacheable by default (RFC 9110 section 15.1 does not list it). A cache stores it only when the response says so with Cache-Control or Expires.

HTTP/1.1 303 See Other
Location: /orders/1042/thanks

See Other

location = /old-page {
    return 303 https://example.com/new-page;
}

Redirect 303 /old-page https://example.com/new-page

header('Location: https://example.com/new-page', true, 303);
exit;

res.writeHead(303, { Location: 'https://example.com/new-page' });
res.end();

from flask import redirect

return redirect('https://example.com/new-page', code=303)