You can do this using the Bookmarks Checker and Bookmarks clean up Chrome extensions. They can check all your bookmarks and identify the ones that seem broken.
Bookmarks Checker
It scans your bookmarks, and you get a report for each folder that looks like this:
Bookmarks clean up
It scans your bookmarks and displays the broken ones under four different categories: “403 Forbidden”, “404 Not Found”, “Unknown Error” and “Request Timed Out”:
Final Words
In my experience, both tools yield very similar results, so pick one, and that should do the trick.
Some of the bookmarks identified by these tools might be false positives, as some websites identify that a tool rather than a real user has tried to access them. So, after scanning, it’s better to check the flagged bookmarks yourself and delete them manually.
Also, using these tools might get you blocked from websites that use Cloudflare for security (especially if you have many bookmarks from the same site):
If you have bookmarked a specific webpage rather than a whole website, before deleting the bookmark, it is worth checking on the Internet Archive if the page is still accessible there.