Presented By The Number 4

Ah yes, the number that haunts every web developer's dreams. You know you've made it as a developer when you can instantly recognize the entire 4xx family tree: 400 Bad Request (your fault), 401 Unauthorized (forgot the token again), 403 Forbidden (nice try hacker), 404 Not Found (the celebrity of error codes), and the dreaded 418 I'm a Teapot (because why not).

The number 4 is basically the harbinger of "something went wrong on the client side" – which in production usually means it's time to check if the frontend dev remembered to actually send the auth headers, or if the user is doing something creative like trying to access /admin with their regular account.

Fun fact: HTTP status codes in the 400s mean client errors, while 500s mean server errors. So when you see a 4, you get to blame someone else. When you see a 5, that's all you, buddy.