On 0 servers with real players, out of 1 Steam servers that run it now, fakes and empty ones included. Checked 00:16 UTC.
de_prob_mill is a community bomb defusal map: the Terrorists plant the bomb, the Counter-Terrorists stop them or defuse it. It is not one of the maps that come with the game, so servers send it to players from the Workshop when they join.
Over the last 30 days de_prob_mill was the #1652 map on CS2 community servers, with <1 real players on it at any moment on average - 0% of everyone playing. It ran on about 0 servers with real players at a time. Right now 0 people play it on 0 servers. It is busiest on Wednesday around 02:00 UTC and quietest on Monday around 00:00 UTC.
Right now 0, on 0 servers from the Steam server list. Over the last 30 days it had <1 real players on average at any moment. Fake servers and bots are not counted, and Valve matchmaking is not in the list.
On Wednesday around 02:00 UTC. The grid above shows every hour of the week in your own time zone.
The busiest right now: Lets Play Casual (0 players). The full list is under "Servers running it now", and every server has its own page with its history.
de_mirage43,372 players on average
de_dust217,938 players on average
sandstone_fb14,457 players on average
de_mirage_fps6,347 players on average
awp_lego_25,436 players on average
awp_lego_2_fb4,846 players on average
de_mirage_christmas2,845 players on average
<null>1,272 players on average
bhop_emevaelx31,056 players on average
duels_mirage_1x11,022 players on average
de_inferno911 players on average
de_nuke782 players on average