HTTP sta­tus codes are the response sta­tus codes that noti­fy users and search engine bots about what hap­pens between the brows­er and the serv­er. HTTP sta­tus codes are espe­cial­ly impor­tant for Search Engine Opti­miza­tion (SEO.) They pro­vide direct infor­ma­tion on the health of a web­site and help pin­point pos­si­ble prob­lems with request­ed content.

When a user sends a request to view a spe­cif­ic web­site by typ­ing the URL in the address bar or click­ing a link, the serv­er responds to this request. Depend­ing on what hap­pened on the web­site, the serv­er can send dif­fer­ent HTTP sta­tus codes back to the brows­er. If every­thing is work­ing prop­er­ly, the brows­er will receive an HTTP code 200 along with the con­tent. If the request­ed web­site or page could not be retrieved, the serv­er will send back an error HTTP sta­tus code. These error sta­tus codes pro­vide infor­ma­tion about exact prob­lems serv­er has encoun­tered and gives valu­able hints about what to do next.

HTTP Status Code Classes

Depend­ing on their type, HTTP sta­tus codes are divid­ed into sev­er­al classes:

• 1XX — Infor­ma­tion­al. The serv­er acknowl­edges the request and noti­fies client to wait for the final response.
• 2XX — Suc­cess. The serv­er acknowl­edges, receives and suc­cess­ful­ly ful­fils the request.
• 3XX — Redi­rec­tion. The request has been received, but the serv­er is redi­rect­ed to anoth­er resource.
• 4XX — Client error. The con­tent is not show­ing due to an error on clien­t’s side.
• 5XX — Serv­er error. The con­tent is not show­ing due to a serv­er-relat­ed error.

The most important HTTP Status Codes for SEO

Not all of these sta­tus codes are impor­tant for Search Engine Opti­miza­tion, but many of them pro­vide valu­able infor­ma­tion regard­ing the health and func­tion­al­i­ty of a web­site. Almost all of them have a neg­a­tive impact on user expe­ri­ence, so it is nec­es­sary to reduce them as much as possible.

Here are the most impor­tant HTTP sta­tus codes:

HTTP Status Code 200 — OK

Every­thing is work­ing per­fect­ly. Vis­i­tors can access all of your con­tent with­out issues.

HTTP Status Code 301 — Moved permanently

The con­tent has been moved per­ma­nent­ly and the serv­er has redi­rect­ed the brows­er to the new URL. The 301 per­ma­nent redi­rect also means that all the link equi­ty — some­thing also called SEO juice, the pow­er of incom­ing links — is now being passed to the new URL. When a web page is being per­ma­nent­ly moved, a 301 redi­rect should be used at all times.

HTTP Status Code 302 — Temporary redirect

This redi­rect is tem­po­rary and does not pass the link pow­er to the new des­ti­na­tion. A 302 redi­rect is telling the search engine that this is a short-term solu­tion (due to redesign or repairs) and that the redi­rect will be short­ly removed.

HTTP Status Code 403 — Forbidden

The page request­ed was found by the serv­er, but the user may not have per­mis­sion to access the page, or needs an account of some sort. This error can also indi­cate that your web­site is incor­rect­ly set up, has a cor­rupt .htac­cess file, or that the file per­mis­sions on your web­site are not prop­er­ly defined.

HTTP Status Code 404 — Not found

The page request­ed was­n’t found by the serv­er. This can hap­pen due to the con­tent being moved and not prop­er­ly redi­rect­ed, or due to some tech­ni­cal issues with the web­site. It is also pos­si­ble that the user types a non-exis­tant URL into the address bar.

404 errors are a nor­mal part of every site. They do not hurt your SEO direct­ly in terms of how many 404 errors a web­site has. How­ev­er, 404 errors have a neg­a­tive influ­ence on your posi­tions in SERP if the rank­ing URLs result in 404 sta­tus code for a longer period.

With respect to the user expe­ri­ence, 404 errors are very dam­ag­ing to your web­site. You should be check­ing your web­site on a reg­u­lar basis and fix all 404 errors for con­tent that still exists but the link is bro­ken, for what­ev­er rea­son. For con­tent that does­n’t exist any­more, it is rec­om­mend­ed to cre­ate a cus­tom 404 page. This gives addi­tion­al infor­ma­tion to users, explain­ing why they are encoun­ter­ing this error and show­ing them alter­na­tives. A qual­i­ty 404 page can pre­vent users from bounc­ing back and keep them on your web­site longer.

HTTP Status Code 410 — Gone

This is an even more def­i­nite sta­tus than a 404 error. It means the page is no longer avail­able and no for­ward­ing page has been set up. If you have any links point­ing to such pages, you should remove them immediately.

HTTP Status Code 500 — Internal Server Error

This is a gener­ic error encoun­tered on the serv­er, giv­en when there are no spe­cif­ic expla­na­tions as to why the prob­lem has occurred.

HTTP Status Code 503 — Service Unavailable

This is a more pre­cise type of 500 error and shows when there are tem­po­rary over­loads of the serv­er or some­times due to main­te­nance. These errors are usu­al­ly beyond the con­trol of the web­site own­er. How­ev­er, if 503 errors are too fre­quent, it is a sign to ask for a serv­er opti­miza­tion or even to change your host­ing ser­vice.