[delroth]

We introduced some opt-in telemetry in dolphin-emu.org several years ago. I remember several times we discovered things we would likely have completely missed otherwise:

- We found out by looking at the distribution of software version that we had a strong holdout on one specific revision. It turns out we had a regression in a niche feature which was very important to a sub-community of our users, and users were basically telling each other to just use that old version. No bug report was filed until we found out via analytics and asked.

- We have a "game quirks" mechanism where the emulator reports weird edge cases that happen very rarely. Current list: https://github.com/dolphin-emu/dolphin/blob/master/Source/Co..., example usage: https://github.com/dolphin-emu/dolphin/blob/ffdc8538a162b1ca... . We used this to find games that use currently unimplemented or stubbed features.

- The list of popular games being played on the emulator was extremely surprising because it turns out there's a huge disconnect in what most NA/EU players are playing and what JP players are playing. This led to us adding a bunch of new games to the list we regularly test for performance and stability regressions. Would you have guessed that Inazuma Eleven GO: Strikers 2013 is in the top10 of emulated games on Dolphin?

[skeaker]

This is a fascinating answer that has persuaded me to your side. I recall opting out of Dolphin telemetry because I simply couldn't be bothered to check what would be sent, but seeing not only examples of what data is sent but also how it's used in such a positive way will definitely have me turning the telemetry on next time I go to use it.

[delroth]

We have a privacy policy which describes what we collect in a bit more details, see https://dolphin-emu.org/docs/privacy/

https://github.com/dolphin-emu/dolphin/blob/master/Source/Co... is the actual code which collects most of the information. We do multiple things to avoid being able to track user activity too much -- for example, while every instance of Dolphin has a unique ID so we can do things like unique counts, events that happen within a play session are associated to truncated_hash(unique ID + game ID) and not directly with the unique ID. This means that we can only correlate events from the same user playing the same game, but not* two events from one user playing different games.

* Our implementation is a bit weak given that the set of all gameids is small and enumerable. We could probably do better there.