HTTP status codes are three-digit numbers returned by a web server in response to every browser request. They tell the client whether the request succeeded, was redirected, or failed — and why. Understanding these codes is essential for web developers, DevOps engineers, and SEO specialists debugging issues with websites and APIs.
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How to Use the HTTP Status Code Reference
Every time your browser loads a web page, the server responds with an HTTP status code that indicates whether the request was successful. This reference tool helps you quickly look up any status code, understand what it means, learn what causes it, and find out how to fix it when things go wrong.
Step 1: Search or Browse
Type a status code number (like 404), a name (like "Not Found"), or a keyword (like "redirect" or "timeout") into the search box. The list filters in real time as you type. Alternatively, use the category tabs to browse all codes within a specific range — 1xx for informational responses, 2xx for success, 3xx for redirections, 4xx for client errors, and 5xx for server errors.
Step 2: Click to Expand Details
Each status code card shows the code number and its name at a glance. Click any card to expand it and reveal a detailed explanation, common causes, and practical steps to fix the issue. Click again to collapse it. You can have multiple cards expanded at the same time for easy comparison.
Step 3: Copy the Code
Use the copy button on any card to copy the status code and name to your clipboard, formatted as 404 Not Found. This is useful when writing documentation, logging bugs, or communicating with teammates about specific HTTP responses.
Understanding HTTP Status Code Categories
HTTP status codes are grouped into five categories. 1xx (Informational) codes indicate the server has received the request and is continuing to process it. 2xx (Success) codes mean the request was successfully received, understood, and accepted. 3xx (Redirection) codes tell the client it must take additional action to complete the request, usually by following a new URL. 4xx (Client Error) codes indicate something is wrong with the request itself — the URL doesn't exist, authentication is missing, or the request is malformed. 5xx (Server Error) codes mean the server failed to fulfil an otherwise valid request due to an internal problem.
When to Use This Reference
This HTTP status code reference is ideal for web developers debugging API responses, DevOps engineers troubleshooting server logs, SEO specialists auditing website health via crawl reports, and anyone encountering unfamiliar error codes in their browser. The search feature makes it faster than scrolling through lengthy documentation or specification pages.
Frequently Asked Questions
Is this HTTP status code reference free to use?
Yes, completely free. This reference runs entirely in your browser with no ads, no signup, and no usage limits. You can search and explore all HTTP status codes as many times as you need.
Is my data safe when using this tool?
Yes. Everything runs locally in your browser using JavaScript. No data is sent to any server. Your searches and browsing activity stay on your device.
What is the difference between 4xx and 5xx status codes?
4xx status codes indicate client errors, meaning the problem is with the request itself (wrong URL, missing authentication, etc.). 5xx codes indicate server errors, meaning the server failed to fulfil a valid request. In short, 4xx means the user did something wrong, 5xx means the server did something wrong.
What does a 301 redirect mean vs a 302 redirect?
A 301 is a permanent redirect, telling browsers and search engines that the resource has permanently moved to a new URL. A 302 is a temporary redirect, meaning the original URL is still valid and the redirect is only temporary. Use 301 for SEO to transfer link equity.
What causes a 500 Internal Server Error?
A 500 error means something went wrong on the server but it cannot specify the exact problem. Common causes include syntax errors in server-side scripts, misconfigured .htaccess files, exhausted memory or PHP limits, database connection failures, and file permission issues.
How do I fix a 403 Forbidden error?
A 403 Forbidden error means the server understood the request but refuses to authorise it. Common fixes include checking file and directory permissions, verifying .htaccess rules aren't blocking access, ensuring directory indexes exist, and confirming IP-based access controls aren't excluding you.
What is the difference between 401 and 403 status codes?
A 401 Unauthorized means the client has not provided valid authentication credentials, so the server is asking for login. A 403 Forbidden means the client is authenticated (or authentication is not required) but still does not have permission to access the resource. 401 says 'who are you?', 403 says 'you can't do that'.
What HTTP status code should I use for API responses?
For successful operations, use 200 (OK) for reads, 201 (Created) for new resources, and 204 (No Content) for deletes. For errors, use 400 (Bad Request) for invalid input, 401 for missing auth, 404 for missing resources, and 422 for validation failures. Always use 500 for unexpected server errors.