Is CS:GO down?

Nah, CS:GO isn't down globally. Sometimes servers in specific regions might have issues, but overall the game is running fine. If you can't connect, first thing to do is check your own internet connection. If that's all good, then have a look at the CS:GO Twitter page or Steam Community forums. They usually post updates if there's any widespread outage.

Actually, I had a bit of trouble logging in earlier today, but it turned out my firewall was blocking CS:GO. Make sure to check your firewall settings or any other security software you have that might mistakenly block the game. After adjusting that, I was back to defusing bombs in no time!