Why They Matter, What They Mean, and How to Fix Them
Whenever you browse the internet, your browser and the website’s server are constantly “talking” behind the scenes. Most of the time, everything works smoothly—you type in a URL, hit enter, and the page loads instantly. But when something goes wrong, you’ll likely see an HTTP error code, a standardized message that tells you what broke and why.
These codes may look confusing at first, but learning what they mean can save you time, frustration, and unnecessary troubleshooting. Whether you’re a website owner, developer, marketer, or everyday internet user, understanding HTTP error codes helps you diagnose issues quickly and know when it’s the website’s fault—not yours.
This is the ultimate guide to every important HTTP status and error code, written in clear language so anyone can understand it.
What Are HTTP Status Codes?
HTTP status codes are numeric messages returned by a web server whenever your browser makes a request. They’re grouped into five main categories:
- 1xx — Informational
- 2xx — Success
- 3xx — Redirection
- 4xx — Client Errors
- 5xx — Server Errors
Knowing what each group means helps you instantly pinpoint where the problem lies—your device, the website, or the server.
1xx Codes — Informational Responses
These codes let you know that the request was received and is still being processed. They appear behind the scenes and aren’t typically shown to everyday users.
Common 1xx Codes:
100 Continue
The initial request was received. The client should continue with the request.
101 Switching Protocols
The server is switching to a different communication protocol (e.g., HTTP to WebSocket).
102 Processing
The server is working on the request, especially during long-running operations.
2xx Codes — Success
These codes mean everything is working correctly. They confirm that the server accepted and processed the request without issues.
200 OK
The most common HTTP code. It means the request was successful and the content is returning normally.
201 Created
Used when new resources are created—usually seen in APIs or after submitting forms.
204 No Content
Request succeeded, but the server has nothing to display. Often returned after deleting something.
3xx Codes — Redirection
When the content you’re requesting has moved or requires a different route, you’ll get a 3xx redirection code. These often appear silently during redirects but can also cause issues if not configured properly.
301 Moved Permanently
The page has permanently moved to a new URL. Essential for SEO and site migrations.
302 Found (Temporary Redirect)
A temporary redirect to another URL.
304 Not Modified
Indicates cached content should be used—great for faster loading.
307 & 308 Redirects
Modern versions of 302 and 301, preserving request methods (GET/POST).
Why these matter:
Bad redirect chains or loops can cause slow pages, indexing issues, and wasted crawl budget.
4xx Codes — Client Error Codes
4xx errors mean something is wrong on the user side—although sometimes the website is still misconfigured. These are the errors you’ve likely seen the most.
The Most Common 4xx Errors:
400 Bad Request
The server couldn’t understand your request—often caused by malformed URLs, corrupted cookies, or invalid data.
401 Unauthorized
Authentication required. You either aren’t logged in or the login failed.
403 Forbidden
You’re not allowed to access the content—permissions are restricted.
404 Not Found
The most famous error code. The page doesn’t exist or has been removed.
SEO relevance: Too many 404 errors can hurt user experience and crawlability.
405 Method Not Allowed
The HTTP method (GET, POST, etc.) isn’t accepted for that URL.
408 Request Timeout
The server took too long to respond, usually due to slow connections or overloaded servers.
409 Conflict
Conflicting changes (commonly used in APIs or CMS platforms).
429 Too Many Requests
You’ve hit a rate limit—this happens with APIs or if a bot is crawling too aggressively.
5xx Codes — Server Error Codes
5xx errors indicate that something is wrong on the server side, not your end. These errors often affect large platforms and can cause global outages.
The Most Important 5xx Errors:
500 Internal Server Error
A generic catch-all for server-side problems. Caused by misconfigurations, broken code, or unexpected issues.
501 Not Implemented
The server doesn’t support the action you’re trying to take.
502 Bad Gateway
One server got an invalid response from another server.
Common causes: overloaded proxies, CDN issues, Cloudflare outages.
503 Service Unavailable
The server is temporarily unavailable—often due to maintenance or resource overload.
504 Gateway Timeout
A gateway server timed out waiting for another server’s response.
507 Insufficient Storage
The server ran out of storage space—rare but critical.
Why HTTP Error Codes Matter for SEO
For website owners, HTTP errors are more than technical problems—they impact visibility and rankings.
- Google crawlers monitor error codes directly.
- Too many 404 or 5xx errors signal instability.
- Incorrect 301/302 redirects can dilute SEO value.
- Soft 404s (pages that appear valid but contain error content) confuse search engines.
- Frequent downtime (5xx errors) can deindex pages.
Ensuring clean, correct HTTP responses is essential for technical SEO health.
How to Troubleshoot HTTP Errors
1. Refresh the Page
Many errors resolve with a simple reload.
2. Check Your Connection
4xx errors may appear if your connection fails midway.
3. Clear Browser Cache
Especially helpful for 400 and 404 errors.
4. Disable Browser Extensions
Ad-blockers can cause unexpected client-side issues.
5. Check the Website Status
Use IsItDown.today to confirm if the error affects everyone or just you.
6. Website Owners Should Review Server Logs
They’ll show the root cause immediately.
7. Check DNS or CDN Health
Many major outages begin here.
Common Causes of HTTP Errors
- Server overloads
- Coding bugs
- Misconfigured .htaccess files
- Broken redirects
- Expired SSL certificates
- DNS failures
- Firewall blocks
- Caching conflicts
- CMS/plugin errors
Understanding the code shown helps narrow down the real cause.
Final Thoughts: HTTP Codes Are the Internet’s Language
HTTP error codes may seem intimidating, but they’re simply the internet’s way of communicating. Each code tells a story—what went wrong, why it happened, and how to fix it. Learning them empowers you to troubleshoot faster, understand web performance better, and maintain a healthier, more accessible website.
Whenever you’re unsure whether a site is down for everyone or just for you, tools like IsItDown.today give you instant clarity—helping you interpret these error codes with confidence.