HTTP Status Code

You might say

The page opens to a 404 error. Did I write the wrong link, or was the deployment incomplete?

A three-digit answer from the server about a request: success, redirect, a request problem, or a server failureWhen a page fails to load, 404 indicates a missing route, 400 flags invalid request parameters, and 500 signals an unhandled server crash. Vague UI toasts like 'Load failed' often obscure the root cause, whereas the three-digit HTTP status code in the Network panel tells you immediately which end to debug.

Know first

HTTP Deployment

Status Code

The same page problem, with the status code pointing to which side to check

example.com/save

GET/old-page404The server has no such resource

POST/save500The server failed while handling it

GET/dashboard401The identity was not accepted

GET/home200This request succeeded

500 · The server failed while handling itServer

Check server logs for this request; the page message cannot replace the status code

Select a row to see what it means: the first digit groups the outcome (2xx success, 3xx redirect, 4xx a request problem, 5xx a server failure), and the exact number narrows the cause.

How status codes guide where to look

Read the category first: The first digit groups the outcome: 2xx success, 3xx redirect, 4xx a request problem, 5xx a server failure. Seeing 500 means the frontend is not the first place to look.

The exact number narrows the cause: 404 means the resource was not found, 401 means the identity was not accepted, 400 means the request content did not match the contract. The difference decides the next check.

Where to find it: The browser Network panel records the status code of every request; debugging tools and errors reported by AI agents also print the number directly.

Quick checkChoose the best answer

A form shows a generic network error, and the Network panel reports 500. What should happen first?

Inspect frontend code first because the page renders the messageTreat 500 as a server-side failure and check server logs for this requestRetry repeatedly because the page message says network error

You can say this to an AI Agent

The page returns 404 and the form returns 500. Confirm both status codes in the browser Network panel, then judge each: whether 404 comes from a wrong address or a missing deployment, and where the server fails on 500. After the fix, resend and confirm 200.

Learn next

1Browser DevTools→2HTTP→3Server Logs→

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