Board games:

Brass

http://brass.orderofthehammer.com/

Cards against humanity

https://allbad.cards/

https://cehs.live/ [Latvian version]

Catan

https://catanuniverse.com/en/game/

https://colonist.io/

Codenames

https://codenames.game/ [official]

https://horsepaste.com/

https://jhil.github.io/kodenames/

https://ninjabunny.github.io/KodeNames/

https://www.thecompletelysurrounded.com/games/code/

https://captnemo.in/codenames/

http://codenames.koosvary.com/

https://www.codenamesgreen.com/ [alternative]

https://codenames.dport.me/ [with pictures]

Deception: Murder in Hong Kong

http://ninjabunny.github.io/mihk/

Dixit

https://shmuxit.com/en

Dominion

https://dominion.games/

Mafia / Werewolf

https://www.blankmediagames.com/TownOfSalem/

https://mafia.gg/

https://werewolv.es/

https://www.chickenkoup.com/

Monopoly

https://playmdeal.com/

https://www.covidopoly.io/

Risk

https://www.warzone.com/

Scrabble

https://www.isc.ro/

Secret Hitler

https://secrethitler.io/

https://secret.ethanl.ee/

Spyfall

https://www.spyfall.app/

https://spyfall.adrianocola.com/

https://spyfall.tannerkrewson.com/

The Resistance and Avalon

https://snakeout.tannerkrewson.com/

https://www.proavalon.com/

http://www.theresistanceplus.com/

https://avalon.fun/

Terra Mistica

https://terra.snellman.net/

Terraforming mars

https://terraforming-mars.herokuapp.com/

Uno

https://play.unofreak.com/

https://duowfriends.eu/

Wavelength

https://longwave.web.app/

https://heretothere.app/

https://gjeuken.github.io/telewave/

Cool online games

Geo Guessr

https://www.geoguessr.com/

• idea : team is given picture and have to figure (guess!) out location of that place as accurate as possible

Draw and guess

https://skribbl.io/

https://sketchful.io/

https://www.drawasaurus.org/

https://rocketcrab.com/

https://drawphone.tannerkrewson.com/

https://drawception.com/login

Word games

https://scattergoriesonline.net/

http://www.keiranking.com/apps/gary/

https://www.outofcontext.party/

Nonograms (Japanese crosswords - SOLO only)

https://nonograms-katana.com/

https://www.nonograms.org/

Trivia and quizes

Sporcle

https://www.sporcle.com/

• Insane ammount of quizes about everything for free.
  

Board game platforms:

The Board Game Arena

https://boardgamearena.com/

• 300+ board games
• web site with many official board game virtual versions.
• free: can host Carcassone, Saboteur, 7 wonders. allows to join other premium games. all original artwork.
• paid: 2-4 EUR/month, almost every popular board game that exist
• cross-device play
• have both live and turn-based versions.

Yucata

https://www.yucata.de/

• 120+ board games
• completely free, no ads
• [have not yet tried]

BrettspielWelt

http://www.brettspielwelt.de/?nation=en

• 50+ board games
• originally in German, have English version
• [have not yet tried]

Tabletopia

https://tabletopia.com/

• 1500+ board games
• mostly paid, some free
• [have not yet tried]

Boiteajeux

http://www.boiteajeux.net/

• [have not yet tried]

Happy Meeple

https://www.happymeeple.com/en/

• 10 board for only 2-players
• 11 games : Lost Cities, Hanamioji, Cartographers, Keltis, Circle the Wagons, Finito, Glastonbury, Level x, Migrate, Siberia,
• [have not yet tried]

Playing Cards

https://playingcards.io/

• implements many 2 player games, definately worth to try

Mattle

https://mattle.online/

• free
• 6 games : Go, Azul, 7 Wonders Duel, Splendor, Century: Spice Road, Blokus

Paper games

https://papergames.io/

• free, no registration
• 4 games : BattleShip, Tic Tac Toe, Connect 4, Gomoku

Netgames

https://netgames.io/games/

• free, no registration
• 7 games : Werewolf, Codewords, Secret Hitler, Spyfall, Love ltter, Avalon, Enigma.

Fun Node

https://www.funnode.com/

• few classic board games
• free

Super duper games

http://superdupergames.org/

Overview of many sites

https://www.flcc.edu/pdf/studentlife/OnlineBoardGames.pdf