Today a question about the size of the browser add-on market came up and more specifically, what kinds of things people used browser addons for. I spent a little time at AMO to try and find some answers--at least for Firefox.

First the AMO statistics site shows that there are almost 200 million addons in use and that number continues to show healthy growth for the last few months. AMO lists over 5000 add ons. The most popular is Adblock Plus with almost a million weekly downloads.

I classified the top 100 addons on AMO according to the following categories:

• context - addons that mash pages together, pull information from one place and put it in another, or otherwise modify the in-page browsing experience.
• download helpers - addons that manage the downloading process or allow downloading of videos, MP3, and photos from sites like YouTube.
• chrome - addons that modify the browser chrome in some way such as adding color to the tabs or modifying the browser's search field
• convenience - addons that make using the browser more convenience such as making bookmarking simpler or adding screen capture capabilities.
• programming and Web design - addons that make debugging Javascript and creating Web sites easier.
• security, privacy, and safety - addons that aim to make the browsing experience safer
• cross browser - addons that support using more than one browser (such as bookmark syncing)
• performance - addons that enhance Firefox performance

The following table shows the percentage of the top 100 addons that fall into each category:

The least popular of the 100 most poplar addons was ReminderFox and it gets 17,500 weekly downloads. This is an impressive list and speaks volumes to the power of Mozilla's distribution through the Firefox browser and the willingness of people to install addons to customize their browser.

Many of these addons have a "contribute" button that allows people to donate to their favorite addons. I wish I knew what kind of revenue was being generated by that, but I couldn't find any statistics on it.

The "other" category had two special entries: Greasemonkey (240,000 weekly downloads) and iMacros (28,000 weekly downloads). Greasemonkey allows you to run scripts written by other developers and consequently functions as a universal browser extension. iMacros allows you to record and play back oft-repeated interactions with the browser.

The Greasemonkey script repository lists 66,000 Greasemonkey scripts. Many of the top 100 seem to be in Russian (I'm assuming they are associated with a game). Many of the other top scripts have something to do with enhancing Facebook and other Web pages or gaining an advantage at Farmville and other games. The total downloads for each of these GM scripts are impressive ranging from 2.5 million for the top GM script to around 300,000 for the 100th.

I think the numbers along make a clear case that people value being able to customize their browser experience and willing to overcome some amount of friction to accomplish it. The question of what monetary value they might attach to this is unproven. I don't think it's a stretch to think you could get people to pay to get an advantage in a game--people do that all the time. Would they pay for a better Facebook? I don't know.

Of course getting people to pay directly is only one way to create value from a browser addon. You can also present people with an addon that gives them a better experience (say the opportunity to save money) and get someone else to pay for it (the retailer) or one that offers in-app sales of something the user will pay for (like music).

Meanwhile, if you'd like to try out our version of the universal browser extension, head over to apps.kynetx.com and install one. Then install a second. I think you'll like the experience and they're all free.