Visually perfect, unfortunately after checking the links it logs me out of most sites where I'm logged in. Caused by checking the "Logout" link if it can be accessed from that page. Would it be possible to omit this link from the check?

This add-on works great! Seems to work fast and reliable. The highlights make it easy to discover redirects and broken links.

Would be great if it also worked in Firefox's built-in XML and JSON viewer, but I guess that is a limitation of the WebExtensions-API?

Nice extension! Request: Change colors? The chosen "standard" shades are fairly useless for red/green colorblind folks.

A hint that may help someone w/ a similar problem as I: I used this to identify broken links in my video collection after a data disaster. It took too long for it to scan each video file (TBs of data), so I made a "shadow" directory w/ all the same dir structure and file names but zero length files:
$ mkdir JustNames
$ find tv -type d -exec mkdir "JustNames/{}" \;
$ find tv -type f -exec touch "JustNames/{}" \;
Copied my html file to that dir (overwriting the zero-length version of it) and Link Checker processed >2,000 links in seconds.

I wish we could have a list of all the links and select what we want to open in new tabs

Response to developer: Thanks :)

Works like a charm ... thank you!