Siteimprove can find error pages that show up with the Status Code 200 OK and make them appear as broken links (they are called Soft 404 errors).
A Soft 404 is when a page returns a 200 HTTP status code even though the page contents indicate that the page could not be found. Since the message or text in Soft 404 pages varies from website to website, we configure these results on a case by case basis. By default, Siteimprove will not show those links as broken.
They could for example show messages like "Soft 404 error", "Page could not be found", "This page is empty", "Object not found", or there could be Soft 404 errors in other languages. Examples: "Die Seite wurde nicht gefunden", "Keine Seite vorhanden", "Ett fel har inträffat", "Vi kan ikke finde den side", etc. Another indication for a Soft 404 Error could be the URL that ends on something like "/404error.html".
If you want Siteimprove to find Soft 404 errors on your website and display them in Quality Assurance, then please send a ticket to our support team with a link to a page with a Soft 404. We can set these up to be identified as broken links based on your preferences.
After the setup you will see the Soft 404 errors within the broken links table in Quality Assurance.
A screenshot showing Soft 404 HTTP status codes