Play well
Browser games are built to bring you back.
Idle Pixel's timers stop after eight hours offline, Tanoth hands out ten free adventures a day and OGame players hide their fleets before bed. Each is fair design, and each works on habit.
Timers and check-ins
Idle and timer games reward coming back at the right moment. If you notice that you open a tab out of habit rather than interest, set your own limit, or pick a game that waits for you, such as Angband or a text world.
Spending
Decide a monthly limit before the first purchase. Premium currencies hide real prices, so convert them back: on Tanoth's wiki, €4.99 buys 80 Bloodstones. Prefer purchases that say exactly what they do over anything with a random result.
Accounts
Name-and-password sign-ups cannot recover a lost password by email, so keep it somewhere safe. A guest save lives in one browser and disappears if you clear its data.
Chat and other players
Shared worlds come with strangers. Every game here has rules about language and harassment; use the ignore and report commands, and keep personal details out of public channels. In MUME, OGame and Ikariam other players can attack you, and Tanoth has an arena; in Discworld MUD only if you opt in.
Younger players
Check the age rule on each tag first: Elvenar is for 16 and over under InnoGames' terms, Tanoth carries USK 16, and Ironwood RPG asks under-18s to play with a parent's permission. Text worlds and chat channels are hard to supervise from across the room, so talk about what your child is playing and with whom.