{"id":16127,"date":"2025-07-24T18:12:13","date_gmt":"2025-07-24T16:12:13","guid":{"rendered":"https:\/\/surver.nl\/?post_type=kennisbank&p=16127"},"modified":"2025-08-21T12:39:13","modified_gmt":"2025-08-21T10:39:13","slug":"status-code-412","status":"publish","type":"kennisbank","link":"https:\/\/surver.nl\/en\/kennisbank\/statuscode-412\/","title":{"rendered":"What does status code 412 Precondition Failed mean?"},"content":{"rendered":"
\"\"<\/figure>\n\n\n\n

Some HTTP errors are clear. A 404 means something doesn't exist. A 403 says you're not allowed to access something. But a 412 status code? That one is less common, and therefore raises all the more questions.<\/p>\n\n\n\n

Yet technically it is a logical error message. Not a broken URL, not a syntax error. Just: a condition that is wrong. Or rather: a condition that you, the client, set, but that the server does not agree with.<\/p>\n\n\n\n

What exactly does a 412 do?<\/h2>\n\n\n\n

The 412 Precondition Failed error occurs when you make a request with a certain precondition, and that precondition turns out to be no longer valid.<\/p>\n\n\n\n

It often involves headers like If-Match or If-Unmodified-Since. With these, you are basically saying, \"I only want to perform this update if the version of the file is still exactly as it was when I last retrieved it.\"<\/p>\n\n\n\n

If that state has since changed, because another system or user has already modified the file, the server breaks the transaction. And returns: 412.<\/p>\n\n\n\n

You asked something, but with an insert. And the server says: that's not right anymore. We're not going to do it.<\/p>\n\n\n\n

When do you encounter this error?<\/h2>\n\n\n\n

Almost always in APIs or applications where versions or synchronization are involved. For example:<\/p>\n\n\n\n