Is Counter-Strike on Steam?

No. Counter-Strike is not distributed on Steam, so there is no Steam Charts or SteamDB player count for it. Its live popularity is tracked here via Twitch viewership instead.

What platforms is Counter-Strike on?

Counter-Strike is available on Linux, PC (Microsoft Windows), Mac.

When did Counter-Strike release?

Counter-Strike released on November 9, 2000.

Counter-Strike

Nov 9, 2000ShooterLinuxPC (Microsoft Windows)Mac

Counter-Strike — frequently asked questions

Is Counter-Strike on Steam?: No. Counter-Strike is not distributed on Steam, so there is no Steam Charts or SteamDB player count for it. Its live popularity is tracked here via Twitch viewership instead.
What platforms is Counter-Strike on?: Counter-Strike is available on Linux, PC (Microsoft Windows), Mac.
When did Counter-Strike release?: Counter-Strike released on November 9, 2000.

About Counter-Strike

Play the world's number 1 online action game. Engage in an incredibly realistic brand of terrorist warfare in this wildly popular team-based game. Ally with teammates to complete strategic missions. Take out enemy sites. Rescue hostages. Your role affects your team's success. Your team's success affects your role.

Summary via IGDB.

Counter-Strike on Wikipedia

Counter-Strike (CS) is a series of multiplayer tactical first-person shooter video games, in which opposing teams attempt to complete various objectives. The series began on Windows in 1999 with the release of the first game, Counter-Strike. It was initially released as a mod for Half-Life that was designed by Minh Le and Jess Cliffe before the rights to the mod's intellectual property were acquired by Valve, the developers of Half-Life, who then turned Counter-Strike into a retail product released in 2000.

Source: Wikipedia (text under CC BY-SA 4.0).