Discovery. People who are interested in finding new add-ons browse these sites. You’ll be in front of an audience of early-adopters who are interested in experimenting. This can be very powerful if you’re trying to solve a problem that applies to a lot of people, rather than a more niche issue. Most people won’t invest the time to try your plugin unless it’s offering a solution to a specific and painful problem, but this audience is curious and more willing to take a chance.
Legitimacy. Nobody’s heard of you. Unless you’re a big company or celebrity, or you’re targeting a niche audience in an area where you are well-known, you’re a stranger who wants to install software on their computer. This sets a very high trust barrier to overcome! Distribution sites effectively lend their sponsor’s reputation to your add-on, making people feel comfortable installing the add-on because they know the sponsor has a lot to lose if they do distribute something malicious. To protect their reputation, the sites generally have a vetting process to check add-ons before they’re allowed on the site.
Promotion. Distribution sites exist to show off all the cool extensions that exist, and are generally set up by the creators of the main app. Having a good collection of add-ons is an important selling point for the browsers, and so some extensions are included in their established marketing efforts. If your add-on gets picked as a great example, and prominently featured in their marketing, you’ll reach a lot of people. This will usually happen after you’re an established add-on, with proof that you appeal to a large audience already, so don’t make any plans that rely on this, but it’s a great bonus if it does happen.
So, getting on a distribution site is a good idea. How do you do it? For PeteSearch, I’ve only made it onto the Firefox site so far, so I’ll focus on that process, but I’ll be attempting to get the IE conversion up on Windows Marketplace soon, I’ll cover the practicalities of their vetting process once I have.
To get started with Firefox, go to their addons site and register as a new user. Once you’re registered, you can then upload the extension you’ve created. You’ll need to provide information about it, and some basic checking will be done when you upload the file, to make sure it supports the correct versions of Firefox for example. Once you’ve got it uploaded, you then chose to make it publicly visible. This places it into the sandbox, which is a sort of purgatory for plugins, where they wait to be approved. They are only visible to people who create mozilla accounts, and change their account options to make sandbox add-ons appear. The idea is to distribute the approval process by getting reviews from people who browse the sandbox, so that the final mozilla reviewers have something to base a decision on. In practice, very few add-ons receive reviews in the sandbox, I’m assuming because very few people are browsing it.
Since an add-on with no reviews will be rejected if you nominate it for the public site, this can be a problem. For PeteSearch, I was able to work around this by gathering links to all of the external reviews, and including them with my developer notes, after it was rejected the first time.