400
ELI5 — The Vibe Check
400 Bad Request means 'you sent me garbage and I don't know what to do with it.' The problem is on YOUR side — you sent a malformed request, missing required fields, or invalid data. Fix your request and try again.
Real Talk
HTTP 400 Bad Request indicates the server cannot process the request due to client-side errors such as malformed syntax, invalid request framing, or invalid data. It signals that the request itself is the problem, not a permissions or server issue.
When You'll Hear This
"It's returning 400 — check the request body format." / "Return 400 if the required fields are missing."
Related Terms
401
401 Unauthorized means 'who are you? Log in first.' You haven't proven your identity.
403
403 Forbidden means 'I know who you are, but you're not allowed in here.' You're authenticated but not authorized.
404
404 Not Found is the internet's most famous error — 'that thing doesn't exist.
Status Code
An HTTP status code is the server's one-line verdict on your request. 200 means 'perfect, here's what you asked for.' 404 means 'can't find it.
Validation
Validation is your backend's bouncer. Before any data gets into the database, the bouncer checks it: 'Is this email actually an email?