There is a common misconception that every time a new release of Firefox comes out Mozilla claims “this is the one that fixes the memory consumption problems”. I see this misconception in action all the time.

The Misconception in Action

Here are some recent examples.

Reddit example 1:

NEXT VERSION OF FIREFOX IMPROVES MEMORY USAGE Holy crap!!! Oh wait, I feel like I’ve heard this before. Oh yea, with ever. single. new firefox release in the last 3 years. Every one.

Reddit example 2:

“Firefox 14 fixes the memory leak problem!” “Firefox 13 finally addresses the leaky memory issue!” “Firefox 12 – better on memory. No more leaks!” “Firefox 11 – finally solving the leaky memory problem.” etc etc etc I’ll believe it when I see it.

Reddit example 3:

Firefox has finally fixed the add-on memory leak for about 10 versions now.

Hacker News example 1:

I’m not sure when Firefox got so memory-hungry and leaky, but it’s the single reason I keep jumping around to Chromium and Opera. Really, really hoping that this time is for real. It’s not the first time a blog post like this has been posted by Mozilla.

Hacker New example 2:

How many releases of firefox have we had now that claim to have fixed its memory problems? I make this at least four, which is a few too many for me to believe it this time.

Ars Technica example:

“Firefox 15 introduces a new optimization that can radically reduce the browser’s memory footprint…” Haven’t they been saying this since Firefox 11?

This drives me crazy, because it’s simply not true.

Debunking the misconception

I looked at the announcements on the official Mozilla Blog for all the releases between Firefox 4 (March 2011) to Firefox 15 (today): 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. Only three of them even mentioned the word “memory”.

Firefox 7. The headline says “Mozilla Firefox Significantly Reduces Memory Use to Make Web Browsing Faster”. The text includes: “Firefox manages memory more efficiently to deliver a nimble Web browsing experience. Users will notice Firefox is faster at opening new tabs, clicking on menu items and buttons on websites. Heavy Internet users will enjoy enhanced performance when lots of tabs are open and during long Web browsing sessions that last hours or even days.”

The headline says “Mozilla Firefox Significantly Reduces Memory Use to Make Web Browsing Faster”. The text includes: “Firefox manages memory more efficiently to deliver a nimble Web browsing experience. Users will notice Firefox is faster at opening new tabs, clicking on menu items and buttons on websites. Heavy Internet users will enjoy enhanced performance when lots of tabs are open and during long Web browsing sessions that last hours or even days.” Firefox 13. The text includes: “Firefox loads tabs on demand when restoring a browsing session to more quickly get you to Web pages. Firefox first loads the tab you are currently viewing, then loads background tabs when you click them. It’s an improvement that makes Firefox start faster and use less memory.”

The text includes: “Firefox loads tabs on demand when restoring a browsing session to more quickly get you to Web pages. Firefox first loads the tab you are currently viewing, then loads background tabs when you click them. It’s an improvement that makes Firefox start faster and use less memory.” Firefox 15. The headline includes: “Firefox Now Uses Less Memory to Make Browsing Faster”. The text says: “Firefox makes your Web experience faster by reducing memory usage when browsing with certain add-ons. The improvements make browsing smoother and more responsive.”

That’s two major mentions of memory consumption, and one minor mention, in twelve release announcements. The major mentions were warranted — Firefox 7 greatly reduced memory consumption for Firefox itself, and Firefox 15 greatly reduced memory consumption in many cases for users with add-ons. And the claims about improvements are clearly qualified to indicate in which circumstances they will be noticed.

But what about the release notes? After all, although they are less prominent than the announcements on the Mozilla Blog, they’re arguably a more official description of the changes in each release. Of the twelve releases since Firefox 4, only four of them had release notes that mentioned the word “memory”.

Firefox 15: “Optimized memory usage for add-ons”.

Firefox 8/8.0.1: “Improved performance and memory handling when using <audio> and <video> elements”.

Firefox 7/7.0.1: “Drastically improved memory handling for certain use cases”.

Firefox 5: “Improved canvas, JavaScript, memory, and networking performance”.

The Firefox 7 and 15 mentions match the release announcements. The Firefox 5 and 8 mentions are minor.

At this point it should be clear that this really is a misconception, with no basis in fact.

What Causes the Misconception?

My best guess is that Chris Peterson nailed it with this comment.

I think the press (overly) publicized the add-on leak fix as it progressed through Firefox’s 6-week release pipeline (Nightly -> Aurora -> Beta -> Release).

In other words, it’s caused by the combination of Firefox’s rapid release schedule and the current intense interest in browser development in the tech press.

For example, a random tech press reader may have heard about the Firefox 15 add-on leak fix multiple times on different sites: on May 8 shortly after it first landed, then again on July 19 when it entered Beta, and then again on August 29 when it was released. (These articles correspond to increasingly prominent blog posts from Mozilla employees and Mozilla itself, such as Kyle Huey’s personal blog, the Mozilla Web Developer Blog, and the official Mozilla Blog.) If that reader wasn’t paying close attention, it’s easy to see how they could end up with this misconception.

It’s an interesting and difficult problem. I think it’s reasonable for Mozilla employees and Mozilla to announce important changes multiple times, at different stages of development, on different communication channels. I also think it’s reasonable for tech press sites to report important changes at different stages of development (especially when you consider that each individual site might only mention a change once or twice). And I don’t think it’s realistic to expect readers to remember which in-development version of Firefox it was that contained some change that they read about two or three months ago.

My only idea for a solution is ad hoc education. So, if you see someone holding this misconception, please point them at this article! Even better, if you can determine how they came to believe it, please let me know.