Question about future added game achievements?

[charlize]

When a Steam game is released without achievements and players have already completed it or played for hundreds of hours, and then achievements are later added, those players often automatically unlock all the achievements they've already earned. But how does Steam know what they've achieved?

I recall playing a game that didn't have achievements when it launched. I played it for hundreds of hours, and when achievements were eventually added, I unlocked all the achievements that I had earned just by playing the game beforehand.

[J4MESOX4D]

The developer retroactively adds the achievements which they can configure around things like save file determinations. This may house back-end stats and the achievements are built around the data they can record. So if a save file contains information about the user getting in excess of 1,000 kills or completing the game on hard then they can create an achievement which detects such.

[Dr.Shadowds 🐉]

It's how the devs set it up. As long devs put check system in their game they can use that same check system to toggle steam API, that how Steam knows.

[JPMcMillen]

It's possible for a game to check to see which achievements you have been awarded for that game. Somewhere on Steam is a game that uses achievements as a checkpoint save game system. But it's mostly used so the game can verify that achievements you've earned in the game were properly awarded on Steam, and if not, try to award them again. So if the recently patched game is doing this, it will know exactly which ones need to be updated with Steam.

Of course, the game could be lazy and just update all earned achievements every time you launch the game. Anything already showing on Steam shouldn't pop a notification so you'd only see new ones if there were any.