Error Page Redirects Should Not Lose Information

Many web applications will implement some kind of redirect on error responses in order to improve how the error is handled for the user (e.g. by displaying a friendly error page with some further information and means of contacting support) or for the business running the website or both (e.g. redirecting obsolete product links in a shop to some related category page with other products the user might be interested in buying.

This is nicer than just leaving the user stranded and displaying some hard-to-understand error code or similar, but it often has the downside of dropping information. For example, server error pages on Twitter/X will sometimes trap you by redirecting to a static error page path, so hitting refresh never actually does anything other than re-loading the error page you're on, even if the underlying error was temporary. In the case of online shops, redirects are sometimes done without even showing you a message that the product you were trying to get to is no longer available, which is bad communication. Another example I just encountered is while loading an invalid DOI, where the error page drops any mention of the DOI I was trying to load, leaving me with no way of checking whether I made a typo or something else went wrong without "retracing my steps" manually.

If you're implementing friendly errors for a website, you should ensure the user has as good a path forward as possible, but also that no information provided by the user is entirely dropped.