Common HTTP status codes

Last Modified on 04/28/2026 1:04 pm EDT

The URL checker checks and returns HTTP status codes.

Quick tips on status codes

If you're looking for broken links, here's a quick rundown of which codes you should care about:

Ignore the 200-level status codes, as these are pages that loaded fine. These are filtered out if you filter by Status set to Fail.
300-level codes are usually used for redirects. These pages do typically load after the redirect. If you review these links, you're usually just replacing the current URL with the one the redirect ultimately ends up on.
400-level codes are generally pages that are broken which you'll want to remove or fix. In some cases false 400-level codes can be thrown.
500-level codes are generally pages where the page or resource requires some kind of authentication or authorization which our automated process can't access.

Once you get more familiar with status codes, filter out the codes that you don't care about when you view the report.

301 response codes

A 301 status code means a resource has a permanent redirect in place.

General tips for the 301 code:

301 status codes are generally safe to ignore, since they indicate a redirect but ultimately a successful resource load.
If you're really only worried about fully broken links, you can safely ignore the 301 code.

When to review 301 response codes

Some authors like to find 301 redirects so they can update the link they're using to the new URL and just avoid the 301 redirect. 301 redirects generally depend on rules existing on a website to handle them, and it's possible those rules might be removed at a future date, so you're avoiding a potential future 404 error by updating links with this respond code.

Refer to Learn the quirks of your broken links report and Tips & tricks for broken links for more information on some of the nuances of working with these codes. For more information on HTTP status codes, refer to the formal HTTP spec or the more readable Wikipedia list of HTTP status codes.

302 response codes

Like 301, a 302 status code means a resource has a redirect in place, though it's a temporary redirect rather than a permanent one.

General tips for the 302 code:

302 status codes are generally safe to ignore, since they indicate a redirect but ultimately a successful resource load.
If you've used Old Links, you may see 302 redirects appear if you have hyperlinks to the old link. While you don't have to resolve these, it doesn't hurt to tidy them up.
If you're really only worried about fully broken links, you can safely ignore the 302 code

When to review 302 response codes

Some authors like to find 302 redirects so they can update the link they're using to the new URL and just avoid the 302 redirect. 302 redirects generally depend on rules existing on a website to handle them, and it's possible those rules might be removed at a future date, so you're avoiding a potential future 404 error by updating links with this respond code.

401 response codes

A 401 status code means "Unauthorized". It's specifically used when a link or resource requires authentication and authentication has either failed or hasn't been provided. This link is definitely broken for anyone who doesn't have the appropriate authentication to view it, which includes our URL checker.

General tips for the 401 code:

We recommend reviewing 401 response codes the first time you run a report.
You may end up ignoring 401 codes in subsequent runs.
If you're referencing protected resources that you have access to but KnowledgeOwl doesn't (such as on a company intranet or behind a VPN), those resources might throw a 401 error code.
Only ignore 401 response codes if you've confirmed that you and your readers can access resources with 401 response codes. This situation is most common for resources that require VPN or some type of login that you and your readers have but our automated checker lacks.

When to review 401 response codes

We recommend reviewing 401 response codes the first time you run a report or the first time you run it after major content changes. Links with this code are broken for anyone who lacks appropriate authentication to log in and view them. A new 401 code can indicate that a previously available public resource now requires authentication, so you may want to replace or entirely remove this link from your content.

403 response codes

A 403 status code means "Forbidden." It's used when a resource requires authentication but the authentication provided does not grant the user access (such as lacking appropriate permissions).

General tips for the 403 code:

We recommend reviewing 403 response codes the first time you run a report.
You may end up ignoring 403 codes in subsequent runs.
If you're referencing protected resources that you have access to but KnowledgeOwl doesn't (such as on a company intranet or behind a VPN), those resources might throw a 403 error code.
Only ignore 403 response codes if you've confirmed that you and your readers can access resources with 403 response codes. This situation is most common for resources that require VPN or some type of login that you and your readers have but our automated checker lacks.

When to review 403 response codes

We recommend reviewing 403 response codes the first time you run a report or the first time you run it after major content changes. Links with this code are broken for anyone who lacks appropriate authentication to log in and view them. A new 403 code can indicate that a previously available public resource now requires authentication, so you may want to replace or entirely remove this link from your content.

404 response codes

A 404 status code means "Not Found." It's used when a resource can't be found at this URL.

General tips for the 404 code:

We recommend reviewing 404 response codes every time run a report.
Only ignore 404 response codes if you've confirmed that they're a false positive. Some websites prevent automated URL checks like these, and that's the most likely reason you'll see a false positive on a 404.

When to review 404 response codes

We recommend reviewing 404 response codes every time you run the URL checker report. These codes generally indicate a website can't be found,.

500 response codes

A 500 status code means "Internal Server Error". It's a catch-all error when a resource can't be accessed but there isn't a more specific reason.

General tips for the 500 code:

Links with this code are definitely broken for everyone, regardless of authentication.
We recommend including 500 codes in every report run. Only ignore them if they feel noisy or unhelpful.

These links are nearly always fully broken and should be addressed.

When to review 500 response codes

We recommend including 500 response codes whenever you run a report. If there's an odd situation where you're receiving 500 errors but links are still working, your best course of action is to contact the website administrator for the problem link to let them know the page is throwing a 500 error.

The code I'm interested in isn't listed here

For more information on HTTP status codes not listed here, refer to the formal HTTP spec or the more readable Wikipedia list of HTTP status codes.

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