HTTP status codes are the three-digit answers a server gives to every request. Not every code is an error; learn the 2xx, 3xx, 4xx and 5xx classes and how they affect SEO.
Key takeaways
- HTTP status codes fall into five classes: 1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error.
- Use 301 or 308 for permanent moves and 302 or 307 for temporary redirects.
- Missing pages should return a real 404 or 410; "soft 404" pages mislead search engines.
- During planned maintenance, a 503 with a Retry-After header helps keep pages from dropping out of the index.
In this article7 sections
When a browser or search engine bot requests a web page, the server answers every request with a three-digit number. This number, the HTTP status code, tells the client whether the request succeeded, whether the page has moved or whether something went wrong. Most users only ever see the 404 page, but every request returns a code behind the scenes, and using these codes correctly matters for both user experience and SEO. This article covers the code classes, the most common codes and how to use them properly.
Status code classes
The first digit indicates which class a response belongs to. Not every code is an error; on a healthy site most requests return 200 or 304.
| Class | Meaning | Example |
|---|---|---|
1xx | Informational: request received, processing continues | 100 Continue, 103 Early Hints |
2xx | Success: the request was processed | 200 OK, 201 Created |
3xx | Redirection: the resource is elsewhere | 301, 302, 304 |
4xx | Client error: something is wrong with the request | 404 Not Found, 403 Forbidden |
5xx | Server error: the server could not fulfil the request | 500, 503 |
2xx: successful responses
200 OK: the request succeeded and the content was returned. Every live page should return this.201 Created: a new resource was created; common in APIs when a record is added.204 No Content: the action succeeded but there is nothing to return, for example after a delete.
3xx: redirects
Redirect codes tell the client that the requested resource lives at another address. This is the class that deserves the most attention for SEO.
301 Moved Permanently: the page has moved for good. Used when a domain changes or a URL structure is reworked; search engines start treating the new address as canonical.302 Foundand307 Temporary Redirect: temporary redirects; the original address is kept.307redirects without changing the request method (for example POST).308 Permanent Redirect: the permanent counterpart of301that preserves the request method.304 Not Modified: the content has not changed and the browser can use its cached copy, saving bandwidth and time.
Avoid redirect chains (A → B → C); point old addresses straight at the final destination. Chains slow down page loads and waste crawl budget.
4xx: client errors
400 Bad Request: the request is malformed.401 Unauthorized: authentication is required.403 Forbidden: even if authenticated, the client has no permission.404 Not Found: the page could not be found. A helpful 404 page that points users to the home page, search or related content is good practice.410 Gone: the page was removed deliberately and permanently.429 Too Many Requests: too many requests were sent in a given time; used for rate limiting in APIs.
Pages that show a "page not found" message but return 200 are a common mistake that search engines flag as "soft 404s". The visible message and the returned code should always agree.
5xx: server errors
500 Internal Server Error: an unexpected error occurred on the server, usually caused by a problem in application code.502 Bad Gateway: a gateway or proxy received an invalid response from the upstream server.503 Service Unavailable: the server is temporarily unable to serve requests. During planned maintenance, send it with aRetry-Afterheader.504 Gateway Timeout: the upstream server did not respond in time.
Persistent 5xx errors can lead search engines to crawl your site less often and, if they last long enough, drop pages from the index.
How to check status codes
The Network tab in the browser's developer tools shows the status code of every request. On the command line, curl -I https://example.com fetches only the response headers. The page indexing reports in Google Search Console list the 404s, redirects and server errors the search engine encountered on your site. Running these checks regularly after a migration or redesign helps you catch problems early.
Conclusion
HTTP status codes are part of the language your site speaks with users and search engines. Correct redirects, consistent error pages and monitored server errors protect both the visitor experience and search visibility. On the sites we build at Dijicrea, we plan redirect maps, error pages and status codes before launch, and during migrations we make sure every old address is passed correctly to its new counterpart.
