400–499 range
When you encounter status codes in this range, you should be concerned. The 400 range indicates that there was something wrong with your request. There are many different issues that can trigger these responses, such as poor formatting, authentication issues, or unusual requests. Servers send these codes back to their clients to tell them that they will not fulfill the request because something looks sketchy.
One status code you may already be familiar with is 404 Not Found. This occurs when your request a resource that the server cannot seem to find. This could be due to a misspelling of the resource or because the page does not exist at all. Sometimes, websites update files on their servers and possibly forget to update the ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access