Post/redirect/get
Answering a successful form submission with a redirect instead of a page, so reloading repeats a harmless GET rather than sending the form again.
Suppose a successful POST answered with a normal page saying "Report saved". If the person presses reload, the browser asks "Send the form again?", and one click saves a duplicate report, or pays twice. The fix is a pattern called post/redirect/get: after a successful POST, answer with a redirect, and let the browser fetch the result page with a fresh GET. Reloading then repeats only the harmless GET.
Try it now
Only the final GET is repeated by a reload, so nothing is saved twice.
Learn it properly
Forms and redirects · GET and POST, validation messages, post/redirect/get, flash messages and CSRF tokens. About 45 minutes.
Other terms from the same lesson
- cross-site request forgery: An attack where another website makes your browser send a request to a site you're signed in to, with your cookies, without you knowing.
- flash message: A one-time note, like "Saved.", that a web app keeps for the next page to show once, usually after a redirect.
- query string: The part of a web address after the ?, holding named values, as in /search?q=fern&page=2.
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