Popular online PC games: what to check before you buy

An online game is only as good as the people playing it, and the rules differ from game to game. Some need a subscription, some are free but sell extras, and some are single-player games that still need a connection. Here is what to check before you buy one, and where to see which games are popular.
What "online" can mean
- Online multiplayer. You play with or against other people over the internet. A game's Steam page lists its modes, such as "Online PvP" and "Online Co-op".
- Co-op. You and your friends play together against the game. Check whether it is online, on one screen, or both.
- Live-service and massively multiplayer games. Games kept running and updated for years, with a shared world or regular seasons. Some charge a subscription; the store page says which.
- Free to play. The game costs nothing and money is spent inside it. The price you see is zero; what you spend is up to you.
- Single-player with an online requirement. Some games that you play alone still need an internet connection or an account.
What to check before you buy
- Are people playing it? The most played page shows how many people are in the busiest games on Steam right now. For a smaller game, the number of recent reviews is a hint.
- Extra accounts and launchers. Some games need an account with the publisher or another launcher, even when you buy them on Steam. The store page lists it.
- Subscriptions and in-game spending. Work out what playing it costs after the purchase, not only the price of the game.
- Where your friends play. Whether friends on another platform can join is something the game's page states. If you buy a key from a shop other than Steam, check its region and platform, as in Steam keys or the Steam store.
- Anti-cheat. Some online games use anti-cheat software that does not run on every system. If you play on Linux or a Steam Deck, read the game's page and recent reviews first.
Buying for a group
For most online games everyone needs their own copy, so the price is multiplied by the number of friends. That makes a few euros of difference per copy worth chasing: compare the stores for each copy, and watch the price over time with the price history on the game's page. Some games include a friend pass that lets someone join without buying the game, and Steam's Remote Play Together lets friends join a local co-op game over the internet. Both are listed on the store page when a game has them.
If the group has not decided yet, put the candidates on your Steam wishlist and paste your profile into the wishlist checker: it shows which of them are on sale right now and where each is cheapest.