Intent to de-support: traditional add-ons

Andrei Hajdukewycz sancus at
Fri Nov 1 21:56:52 UTC 2019

Sorry it's taken me a month to reply to this post. I don't always have 
time to dedicate to statistics work and these sorts of lengthy 
discussions. It took me roughly 2.5 hours to dig through numbers and 
server logs and write this email.

On 10/3/2019 12:35 PM, Eyal Rozenberg wrote:
> Andrei, with due respect, I'd like to partially disagree with what you
> wrote, particularly (but not only) regarding statistics.
> Before doing so, however, I want to ask the list of some clarification
> regarding the methodology with which we gather usage statistics: Under
> what circumstances; which users have stats collected; what happens to
> people whose older versions don't know about ATN; etc. If someone could
> write a few paragraphs about this (or send a link) I'd be grateful.
All versions of Thunderbird ping ATN, because requests to the old AMO 
domains are redirected to us. We even get pings from a few stragglers on 
versions in the single digits.

You can find global Thunderbird statistics on - in 
particular, the percentage of users on each version 
<>. There are roughly 1.5% of 
users on versions 38 and below. 2.5% on 45.*, and 3.5% on 52.*. Plus 
maybe 0.5% on random older betas, mostly 56 because of a weird auto 
update rule. In total, 8% on "old versions"(prior to 60). While quite 
low overall, It's higher than we would like, but a bit lower(~6.5%) on 
weekends, probably due to users stuck on employer-installed versions.
> 1. Quoting an annual 1-2% userbase growth rate does not say much about
> what happened over the past few months, when a lot of extension support
> was lost. Do you have stats for that?
Nothing has happened over the last few months, as you can see 
<>. Extension support is not significant 
to most users. Seasonal variations like summer European vacations, 
Christmas, and Easter have more effect on Thunderbird user numbers than 
any change to extension support ever could. Users did not significantly 
change during last's year's TB60 addonpocalypse either, so I wouldn't 
expect any huge difference when 68 auto updates go out.
> What that means is that treating relatively-low-usage extensions as
> non-representative is myopic; and not significantly catering to
> extensibility blocks most of the potential of user base increase.
Sure, I agree with you. The context here is not "should we support 
extensions or not?" it's - how much work do we put into supporting them. 
We already put in a lot of work, arguably more than the return on 
investment. Add-on developers aren't poorly supported. Add-ons occupy a 
massive amount of work and discussion time from Thunderbird employees. 
If I had to make a wild guesstimate based on my time, Geoff's time, 
Magnus' time, etc, I would say that add-ons consume somewhere around 30% 
of our overall developer time. Magnus could probably give you a better 
estimate. I know I spend roughly 50% of my time working on add-on 
related issues and support. Regardless of the specific number, it is 
quite a bit.

You interpret the substantial support that add-on developers receive as 
insufficient, not realizing that it's almost more than we can afford 
> 3. 1-2% annual user base growth is more of a stagnation than growth a
> slight waning of the user base; the population in countries in which TB
> is popular is growing at a higher rate than that, I would guess. I'm not
> saying that's a bad thing considering the objective circumstances,
> 4. There is a huge difference between the part of the user base who use
> Thunderbird because they made a decision to do so, and people who have
> had Thunderbird pre-installed on their machine for some reason (e.g.
> because they're in some organization with wise IT people). Making claims
> regarding whether people tend to use or not use extensions, whether we
> have growth or decline etc. should really be treating those two
> categories of users separately - even if we can't place users in these
> categories explicitly.
True, but irrelevant. Add-ons have never, and will never drive user 
growth. They may help in small ways with user retention.
> 6. "the 5-10% of users who even install and use add-ons that aren't
> Lightning." - that's a bold statement, that seems to contradict even
> Christopher's partial numbers. Show your stats on this please.
> Eyal
In what way does it contradict them? Keep in mind that user counts for 
each add-on count the same users many times, because you are counted 
repeatedly for each add-on you have installed.

Even assuming the overall average is 2 add-ons per user, if you sum the 
add-ons that aren't Lightning you get 3.2M daily users, divided by 2 for 
multiple counts, which would be ~16%.

However, users are heavily concentrated in the top 10-20 add-ons, many 
of which either should be redundant with core, or part of core in some 
way(ImportExportTools, Provider, Manually Sort Folders) or are already 
on their way to core(Enigmail). If you sum outside of the top 10, 
there's 1.78M add-on users, again divided by 2 to account for multiple 
users, and you're already below 10%. Provider and ImportExportTools 
together account for 23% of all add-on users by themselves.

I do suspect that this guess overstates the number of individual users, 
because I think the average is higher than 2. Calculating statistics on 
number of users that have an add-on installed is possible, but it 
requires setting up some new logging and querying/compiling of those 
statistics. I have added it to my list of tasks, you can track when this 
work is completed in this issue on GitHub 
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