42 Days

In a recent thread on dev.apps.firefox, someone suggested we shift our 6 week release schedule to avoid Microsoft Patch Tuesdays, or other unfortunate timing coincidences. I’m not announcing any changes to our release schedule, but I did make a point there that I want to repeat a little more broadly (and with emphasis added):

Let’s go back to first principles for a minute. Releasing every 6 weeks is a cadence we set for ourselves to satisfy several constraints. Constraints like:

• Delivering security and stability fixes on a regular basis.
• Getting new features out to our users promptly, and being able to iterate on the feedback we receive.
• Containing the amount of code change and change-interaction that happens per release.
• Giving ourselves time to react to problems discovered before release (on Nightly, Aurora, or Beta)

Releasing daily wouldn’t work very well; it runs afoul of the last constraint. Releasing yearly would hurt us on the first 3. But the constraints are just about as well satisfied by 40 days or 44 days as they are by 42 days.

We derive great benefit from our current schedule. It satisfies these constraints much better than the old, monolithic release model did. But that is not to say that we should treat 42-day cycles as inviolate. We will adjust. We will add or drop days, or add or drop weeks when we need to. We’ll be respectful of the fact that other people build plans around our plans, and try not to alter schedules without notice, but at the end of the day we’ll do right by our users first and foremost.

Right now we’re not looking at moving the release to another day of the week (Tuesdays do have some nice properties), or adding a skip week somewhere to take us off-cycle for the next patch Tuesday, but those discussions are absolutely on the table when they make sense.

No religion here. 6 weeks is a nice spot in the constraint space, not a law. The first time we miss it, people will talk about us “slipping,” but the tail doesn’t wag the dog here. Firefox still ships when it’s ready.