Web browsers furthermore do not hinder a user to bookmark a website for a second time. Some may visualize that a bookmark already exists but none will stop the user from bookmarking a web page multiple times.

Bookmark Sentry for the Google chrome browser is a browser extension that can scan all bookmarks for dead and duplicate links.

The extension scans all browser bookmarks automatically after installation. This can take some time depending on the number of bookmarks and the folder structure.

The scanner displays the scan progression in the extension’s options. It shows the bookmark that is currently scanned, the percentage as a bar and number, the last scan, next scheduled scan and the number of problems found (which either means dead or duplicate bookmarks).

Scan results are displayed on the very same screen after a scan for duplicate or dead bookmarks finishes.

The extension displays status codes and text to make it easier for the user to identify the underlying problems. Each bookmark can be removed individually by clicking on the X at the front of each result. There is no option to delete all at once. Links are clickable to manually recheck the bookmark in question.

Bookmark Sentry will scan all bookmarks once a month by default. It is possible to change the interval to another or switch to manual checks only. The only other available preference is the time between connection scans. The default time is 10 seconds, reducing it will increase the scan speed.

Bookmark Sentry is a helpful extension for the Chrome browser. Most users are probably fine with running the extension once to check their bookmarks and disabling or uninstalling it afterwards. Only heavy bookmark users may need to use it regularly.

Update: The add-on has been removed from the Chrome web store. A Chrome extension alternative is not available. Windows users can use AM Deadlink instead which supports the Chrome browser as well.

Check Places for Firefox adds the option to verify all bookmarks in the Firefox web browser. It can be used to check all bookmarks (with the option to exclude folders) or only specific folders that the Firefox user selects.

A click on the check bookmarks button will start the verification. The time it takes to verify the bookmarks depends on the amount of bookmarks and the Internet connection.

It took about a minute to check 489 bookmarks on a fast Internet connection. The add-on will display statistics on the report page including the time it took to verify the bookmarks and the number of bookmarks that got verified.

Errors are divided into the three categories failed pages, duplicates and empty folders. Failed pages are those with dns, page or other errors. These pages can be temporarily or permanently unavailable.

Each bookmark is listed in its own row. Selecting a bookmark will display additional information about the bookmark with the options to open, delete or exclude the bookmark.

The whole process – even if the pages with errors are verified manually – takes less than five minutes to complete.

Check Places is an add-on for the Firefox 3 web browser. It can be downloaded from the Mozilla Firefox website.

Check Places is the first Firefox 3 extension that can check all Firefox 3 bookmarks for duplications and invalid references aka dead pages. The experimental add-on can be downloaded right from the Mozilla website after logging in as a user. The new Check Places entry will be added by the Firefox add-on to the bookmarks menu. A click on that link will open a new window that the user can use to configure the scan behavior.

It is possible to scan all bookmarks or only selected folders. Exclusions can be made so that some bookmarks or folders will not be scanned in the process. The scan itself can check if the pages that the bookmarks point to exist and if it is stored more than once in the bookmarks.

The scan does not take long, a few minutes for a few hundreds bookmarks. The results are displayed in a tabbed interface detailing the bookmarks that have returned a page not found error and those that have been recognized as duplicates.

Each Firefox bookmark can be opened and checked individually. The extension will list the return status of the page, e.g. 404 page not found or 500 Internal server error to aid the user in his decision. A simple timeout for example usually means that the page could be back up later while a 404 usually hints at a more severe problem.

Selected bookmarks or all can be deleted in the end to clean the Firefox bookmarks from duplicates and invalid entries. Check Places is a great Firefox 3 extension, must have for every Firefox user that has more than a handful of bookmarks and indispensable for users with hundreds and more.

It can aid you when you need to import bookmarks from another system to prevent that duplicate entries are added to your bookmark list. It also allows you to search for duplicates in your bookmarks and delete them afterwards. The best feature as far as I can tell is a warning whenever you want to add a site that is already listed in your bookmarks. It displays the location of the old bookmark and prompts the user for action. Possible actions are to add the new bookmark as a duplicate entry or cancel the process.

Other features include the function to backup your bookmarks and a search function that lets you search your bookmarks for names, description or keywords. This can be useful if you have a large amount of bookmarks.

Would not it be great if there was a tool that checked the bookmarks automatically for dead links and duplicate entries ? A tool that would be able to read and check bookmarks in many browsers such as Firefox, Internet Explorer, Opera and Mozilla ? I assume you answered the above questions with yes, if that is the case AM-Deadlink might be the exact program you would like to take a look at.

Am-Deadlink is freeware, just download and install it on your computer.  You have a drop down menu on the upper left corner when you start the program where you chose the browser you want to check. You sometimes have to navigate to the bookmarks folder of that browser manually and select it, but that should not be a big deal.

Now you can check the appearing bookmarks and find duplicates. If the link is dead a 404 error most likely appears in the line of the bookmark. You can now delete that bookmark if you like or leave it there and check later again. Those errors also appear when a website moves host and that process has not finished yet for example. It is always a good idea to check it more often before you delete an entry.

AM-Deadlink has the ability to backup the bookmarks as a zip file, there is unfortunatly no option to import bookmarks from one browser to the other directly. You may export bookmarks in a universal format and import them later through your browser though.