XP is a record of what you have done here. Every award is a row in a ledger with a reason attached, which is how it can be checked and how it can be taken back.
What things are worth
- Completing a help request as the helper: 50 XP
- Your answer being accepted: 25 XP
- A streak milestone: 25 XP
- Finishing a daily quest: 15 XP
- Earning a badge: 10 XP
- A good review after helping: 10 XP
- Writing a post: 5 XP
- A like on your post, an upvote on your answer or resource, a quiz answer, an Arena vote: 2 XP each
Caps and decay
Most reasons have a daily ceiling, so a burst of activity in one evening cannot run away with it. Posts are capped at 15 XP a day, likes at 50. Repeated awards from the same person on the same day are worth less each time, which is what stops two accounts trading likes.
Why your XP can go down
Because credit is attached to the thing that earned it. Delete the post and its XP goes, including XP from its likes. Unlike something and that like's XP goes. Lose a badge and its 10 XP goes with it.
Badges earned before September 2026 were granted without their XP, because of a bug in how the award was recorded. It is fixed, and the XP owed was paid to everyone affected.