Good question. When you search for an crag with 'search & add ascents' (from the main page), and you find a list of routes, there is a F/OS rating. The values vary from 1 to 3. What does it mean? I like 8a.nu, but sometimes I'm missing the 'what is this?' button.
If 100 % has onsighted the route, the index is 3. If 100 % has flashed the route, the index is 2. If 100 % has redpointed the route, the index is 1. We should add a what is this button :-)
F/OS rating?