Whenever you, or say a search engine, request a website from a web server, an HTTP response code is returned, and this response code can tell us a little bit about what happened during that communication. These response codes or these HTTP status codes, show up quite a bit in technical SEO, so I think it's important that we take a minute to review the most common ones.
HTTP Status Codes
- 200 > Ok
- 301 > Moved permanently
- 302 > Found
- 404 > Not Found
- 410 > Gone
- 500 > Internal Server Error
- 503 > Service Unavailable
200: The first one that we see quite often is 200, 200 means okay. This tells the browser, or the crawler, that the request was successful, whatever we asked for came back, and everything worked.
301: If we see a 301, this is essentially a redirection. 301 means move permanently. It means that whatever we asked for has been assigned a new permanent location, and anytime we ask for that old location, we should instead ask for the new location. This is a permanent redirect. So it's basically saying, “Hey, I've moved, and I'll always be over here now.” This is the most common type of redirection that we use in SEO and we often are always checking to make sure that our redirects are 301's.
- Responds with a page from a different location
- Signals the redirect is temporary
- Not a recommended approach
Another type of redirection is 302, and this simply means found. The server is responding to the request with a page from a different location, but it's going to tell the requester that continue using this original address because it's really a temporary redirect. It means I plan to come back to return back to this origin at some point. Now, this approach is really not recommended. It's really not an effective way to instruct search engines that a page or a site has moved, and there are very small use cases when a 302 makes sense.
404 and 410: A 404 is the error code. It's the file not found status code. It means the server didn't find anything that you were looking for, and there's no indication as to whether this is a permanent or temporary condition. This typically happens when someone mistypes a URL, and the server says, “Hey, what you're looking for is not here.” In the 400 codes is also 410, meaning gone. And this is how you tell a crawler that whatever they're asking for is no longer available, and it's never coming back. It means this is a permanent removal, and this is often how to remove content from the search engines.
500 and 503: The last two that you'll encounter are in the 500's, 500 meaning internal server error. This is simply a generic error message, and it's essentially saying there's been an unexpected condition. We've encountered a problem, but I know nothing more about it. And the final error code is a 503, and this means the service unavailable. The server cannot handle the request, either it's temporarily overloaded, it's been shut down, or there's some scheduled maintenance, but a 503 indicates we hope that this problem will be alleviated soon, which means that a crawler or a server may try to come back at a later point.
So these are the most common status codes, and they will come in quite handy as you begin to dive deeper into technical SEO.