Posts in a game's official Steam news feed that announce an update: tagged as patch notes by the developer, or plainly about a patch or a released update.

News checked every 180 days

• An announcement is not a build. Developers can ship updates without a post, or post about several updates at once.
• Untagged posts are recognised from their words, so a few updates are missed and a few other posts may be counted. Tagged posts are marked Patch notes on the Updates tab; recognised ones are marked Update.
• Older posts are being read back through each game's history, most played games first, so months before October 2026 fill in over the coming days.

Source: Steam Web API, ISteamNews/GetNewsForApp. Full methodology