Crystal Math Labs offers an XP tracker for Jagex's Old School RuneScape and RuneScape 3. If you wish to track RuneScape 3 players, click the RS3 link on the top right of any page. This website is currently tracking 1,220,419 Old School RuneScape players with 141,326,357 datapoints since this site's launch on February 23, 2013.
Contributors
Gold and silver crowns next to a player's name on this website do not indicate their moderator status in RuneScape. You can hover your mouse over any player's crown to find out why they have the crown. Here's a list of players with crowns:
Developer:

Donators:
If you're interested in donating, click here.