Simply put, the pack lets players see if a player has advanced to an advancement without telling everyone who made the advancement.

This is good for UHC servers or server with other survival-based minigames but is not remotely recommended for normal play.

• Download anonymous-advancements.zip and place the version-appropriate data pack in your server, realm or singleplayer worldsave's data packs folder.
• If the server is running, type /reload in the chat and press Enter.

Might not work on worlds where other data packs trying to do the same thing are installed.

Made this because someone too dumb to make it themselves kept spamming a forum I frequent with "plez how do make".

Forgot to mention, this is pretty much available in all languages supported by Minecraft, the only gripe is that the word 'Someone' will always appear in English. Not yet compatible with the new 1.16pre-6 piglin advancement that came out last night.