Mozilla is planning to address Firefox add-on compatibility issues as new versions of the browser hit the Web more often.

Mozilla kicked off this summer its controversial plan to release new versions of its Firefox browser every six weeks. The idea, the company has said, is to bring more functionality to its users more often.

In some cases, that change has been beneficial for users who want the updates the browser brings to the market. In other cases, it has proven to be a bit of a problem. One of the most notable issues related to the rapid-release cycle is the impact it has on add-ons.

In a blog post yesterday examining the state of Firefox add-ons, Mozilla add-ons product manager Justin Scott revealed that in these days of rapid-release Firefox versions, the organization is facing difficulty ensuring that all add-ons will be compatible with new versions of the browser.

According to Scott, Firefox has historically assumed that add-ons are incompatible in a new version of the browser by default. In the past, when Mozilla would launch new versions of the browser every year or so, that was often true. But now that it's releasing new versions every six weeks, this is simply not the case.

"When Firefox 6 launched, 97 percent of add-ons compatible with Firefox 5 were still compatible with 6," Scott wrote yesterday. "And we're on track to launch Firefox 7 tomorrow with 99 percent compatibility from 6."

However, add-on compatibility is a relative term in the Firefox ecosystem. Mozilla has been scanning add-ons in its own marketplace but does not do so with the add-ons that aren't hosted through its site. About 75 percent of all the add-ons in use each day--about 450 million--are not hosted in its marketplace.

"So, how do 450 million add-ons get installed if not from addons.mozilla.org?" Scott asked. "Third-party bundling. More and more software tries to plop a toolbar into Firefox when you install it, often without asking you. Java Console alone has more than 100 million installations among Firefox users on Windows, and it doesn't even do anything."

Scott went on to say that many of those add-ons "use their own update mechanisms" to ensure their applications work with the browser, rather than employ Firefox's own compatibility-checking option. The result, Scott says, is confusion and sometimes, issues for users.

But luckily for those folks, Scott says Mozilla has a solution. Rather than just thinking about hosted add-ons, Mozilla will take the compatibility of nonhosted add-ons into account, as well. He said that Firefox will soon be "more trusting of add-on compatibility with new versions" and will no longer assume all add-ons are incompatible with the latest version of the software. The feature will be made available in Firefox 10.

As Scott noted, Mozilla plans to launch Firefox 7 today. So, users will need to wait some time to finally have add-ons default to compatibility.