Firefox add-ons

Add-ons extend Firefox’s functionality, making it one of the most extensible browsers available.

Add-ons are third-party creations that in some cases have contained malicious code, so install only those from sources you trust. Additionally, too many add-ons or even a single poorly written one can bring Firefox to its knees, so promptly uninstall any you do not need.

When selecting an add-on, I look for one that:

  • is open source and multiplatform
  • is actively maintained
  • has active support, whether by developers or users
  • has a good security record
  • does not noticeably affect Firefox’s performance

To install an add-on, use Firefox to browse the repository.


  • Adblock Plus is an advertising blocker. Open source.
  • Ghostery is a behavioral advertising blocker.
  • HTTPS Everywhere encrypts your connections to supported websites by rewriting all requests to these sites to HTTPS. Open source.
  • NoScript is a JavaScript blocker. Open source.


  • Flash Video Downloader downloads videos from YouTube and other supported sites and converts them to your preferred format. After each update you are taken to the DownloadHelper website; this behavior apparently cannot be disabled. TODO: Find an open source equivalent.
  • Open in Chrome adds “open current tab in Google Chrome” to the right click context menu. Also works with Chromium, the open source parent of Chrome. What I do is use Firefox (secure, locked down) as my daily driver, and have Chromium (with out of the box settings) as a backup. When I encounter a page with display issues in Firefox that might be due to my too-high security settings, I use this add-on to easily open the page in Chromium and take action depending on what I see there.
  • Spellcheck dictionaries in different languages. Be careful: it’s easy to accidentally select a language pack instead of a dictionary. License varies by dictionary.
  • Tab Groups replicates the Panorama (aka tab groups) feature removed from Firefox 45.


  • Firebug edits, debugs, and monitors CSS, HTML, and JavaScript live in any web page. Open source. Although Opera Dragonfly is my preferred development tool, Firebug is great for tracking down Firefox-only problems. After each update you are taken to the Firebug website; this behavior apparently cannot be disabled.
  • MeasureIt draws a ruler across any web page to check the width, height, or alignment of page elements. Open source.
  • SeoQuake provides data useful for search engine optimization and web site promotion. Open source. After each update you are taken to the SeoQuake website; this behavior apparently cannot be disabled.

My add-on wish list includes (reader comments wanted):

  • An extension to password protect access to Firefox’s preferences, useful for public kiosks where users tend to mess around with such things.
  • A phishing site blocker similar to PhishTank that works on modern versions of Firefox. There’s the Netcraft antiphishing toolbar, but I dislike how much space it needlessly occupies.


These notes were last updated 6 February 2016 with reference to the soon to be released Firefox 45.


About Warren Post

So far: Customer support guy, jungle guide, IT consultant, beach bum, entrepreneur, teacher, diplomat, over-enthusiastic cyclist. Tomorrow: who knows?
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