HDL® Extension for Firefox


Due to being unusable on recent versions of Firefox, the download links to the extension have been removed. The information below is is purely historical.


Firefox is making major changes to extensions. (See https://blog.mozilla.org/addons/2017/02/16/the-road-to-firefox-57-compatibility-milestones/.) By the end of 2017 the legacy extension APIs used by the HDL Extension for Firefox will no longer be supported. Testing indicates that the extension will no longer work as of Firefox 53, released in April 2017. If you upgrade to Firefox 53, delete the HDL Extension from Firefox's Add-ons.

Users who find the HDL Extension for Firefox indispensable could consider using the Firefox Extended Support Release, version 52, and are encouraged to contact hdladmin@cnri.reston.va.us to inform us of the features of the extension that they find useful to include, should a rewrite of the software be undertaken in future.


A commonly used HTML encoding represents a handle as a URL for a web-to-handle proxy server to resolve, e.g., http://hdl.handle.net/20.1000/5555 or http://dx.doi.org/10.1000/1. The HDL® Extension for Firefox, developed with support from the Defense Advanced Research Projects Agency (DARPA) under Grant HR0011-05-1-0003, will recognize these as "handle URLs", extract the handles, and resolve them.

The URL form of digital object identifiers, aka handles (and DOI® names, which are a branded form of handles) has traditionally been the most common method of using them in web pages. To ensure both backwards compatibility and future compatibility, the extension will precisely mimic the behavior of the web-to-handle proxy servers. That is, there will be no functional difference between clicking on a URL or a URI link for the same handle, given that the extension is installed.

The citation below, represented as a URI link, is an anchor with a handle as the reference value: <a href="hdl:20.1000/5555">. With the extension installed, clicking on the URI will resolve the handle and redirect the browser to the HDL.Net web site home page. One of the values stored with handle 20.1000/5555 is http://www.handle.net. If the extension is not installed, clicking on the link below will result in an error, most likely "The address is not valid."


The extension will also identify handles that are used in web pages as image sources. If the extension is installed, a HDL.Net logo will be displayed below. Firefox loads the image when the page is rendered by finding and resolving the handle in the 'src' attribute of the HTML tag <img src="hdl:20.1000/imageTest">. Without the extension, you see a symbol representing an image file that the browser couldn't locate.




Due to being unusable on recent versions of Firefox, the download links to the extension have been removed.



The extension works with Firefox for Windows, Linux, and MacOS X operating systems.

If there is a previous version of the extension installed, uninstall the previous version before proceeding with the installation of the current version by clicking on Tools->Add-Ons (or Tools->Extensions depending on the platform). The Extensions window will list the Handle Extension. Click on uninstall.



  1. Use Firefox's File menu to open the cnri_handle_extension_for_firefox-2.4.2-fx.xpi file.
  2. Click on the install button after it highlights.
  3. Restart Firefox.


There is a configuration panel at Tools->Options (or Firefox->Preferences on MacOS X) for setting Redirection Options.







Extra web-to-handle proxy sites can be listed to be recognized as handle resolutions.



The source code can be downloaded here.

June 6, 2017