Welcome to DOAB Check!

FEF logo DOAB logo

DOAB Check is a collaboration between the Free Ebook Foundation and the Directory of Open Access Books. It checks each the links in DOAB about once a month, looking for any links that are broken or misconfigured.

We've grouped the links by the publisher's name and by the server url to make it easier for publishers to see whether links they've entered into the DOAB database are working as expected.

We have a few ways to view the results.

Summary of link checks

When a link is checked we record the status code and content type returned by the web server.

  • "214" indicates an unescaped redirect.
  • "301" or "302" indicates a bad redirect.
  • "403" indicates a misconfigured server that is not allowing access to the promised resource.
  • "404" means the link is broken - the resource is not found.
  • "418" means the website was pretending not to be there.
  • "500" means something has gone wrong at the website server.
  • "502" is a gateway error. Some websites use load balancers or content distribution networks; if these gateways have a problem connecting with the source website, they send a 502 response.
  • "503" means that a website couldn’t be reached. This could happen because the server was too busy, under maintenance, or something else. Amazon's robot blocker returns 503 codes, so these must be checked manually.
  • "504" indicates that the server, while acting as a gateway or proxy did not get a response in time from an upstream server.
  • "511" indicates a problem with the security of the connection - most often an incomplete certificate.
  • "524" means the website didn't respond in a reasonable time.
  • "None" or "0" means something has gone terribly wrong. Possibly a bug in the checker or a malformed url.

66,886 links are being checked. Of the 69,607 books and book chapters in DOAB, 4,142 have problems.

HTTP code number of links percent of total
524 251 0.38%
511 51 0.08%
504 17 0.03%
503 2,411 3.60%
502 15 0.02%
500 207 0.31%
418 490 0.73%
404 335 0.50%
403 189 0.28%
301 127 0.19%
214 11 0.02%
200 62,660 93.68%
0 122 0.18%

The doab-check data is available for individual books via an api.