303 リダイレクトチェッカー

A 303 redirect explicitly tells the browser to retrieve the redirected resource using GET, regardless of the original request method. It's primarily used after POST form submissions to redirect to a confirmation page, preventing duplicate submissions when users refresh the page.

303 explicitly guarantees POST-to-GET conversion, while 302's behavior is ambiguous - some browsers might preserve POST, others convert to GET. For the Post/Redirect/Get pattern, 303 is the correct, unambiguous choice that all modern browsers handle consistently.

No, 303 redirects don't pass link equity and aren't meant for SEO purposes. They're functional redirects for user experience, specifically preventing duplicate form submissions. For SEO-related redirects, use 301 or 308 permanent redirects instead.

Use 303 redirects after processing POST requests when you want to redirect to a confirmation page using GET. Common use cases include form submissions, checkout completions, payment confirmations, and any situation where you need to prevent duplicate submissions on page refresh.

Post/Redirect/Get (PRG) is a web development pattern that prevents duplicate form submissions. After processing a POST request, the server sends a 303 redirect to a GET endpoint. If the user refreshes, the browser repeats the harmless GET request instead of resubmitting the form.

303 is rarely used for APIs because it converts POST to GET, which may not be desired behavior. For API redirects that must preserve methods, use 307 (temporary) or 308 (permanent). Use 303 primarily for browser-based form submissions.

All modern browsers properly support 303 redirects and handle the POST-to-GET conversion correctly. Very old browsers might not recognize 303 and may treat it as a generic 300-level redirect. For modern web applications, 303 is safe to use.

Yes, e-commerce sites should use 303 redirects after checkout to prevent duplicate orders. When a customer completes a purchase, redirect them with 303 to the order confirmation page. If they refresh, only the confirmation page reloads, not the payment processing.

Implementation depends on your platform. In Express.js use res.redirect(303, '/confirmation'), in PHP use header('HTTP/1.1 303 See Other') then header('Location: /confirmation'). Always test with our 303 redirect checker to verify correct implementation.

Without a redirect after POST, refreshing the page triggers the browser's 'confirm form resubmission' dialog, and users may accidentally resubmit forms, creating duplicate orders, emails, or database entries. Using 303 redirects eliminates this problem by converting to safe GET requests.