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| Kaasino kaasino.com | Fortaprime SRL | — | 1 |
| Kaboo unknown kaboo.com | Betsson AB | UKGC | 1 |
| Kairosbet kairosbet.vip | Buscarar SRL | Anjouan | 1 |
| Kaiserino kaiserino.com | Wild Blackfin Limited SRL | Anjouan | 1 |
| Kaista kaista.com | Project Vanir Limited | Estonia | 1 |
| Kajot Intacto kajotintacto.cz | Kajot | Czechia, Slovakia | 2 |
| Kalevala Kasino kalevalakasino.com | Esports Entertainment Group | MGA | 1 |
| Kalooki Sportsbook kalookisportsbook.co.uk | Kalooki Sportsbook Limited | UKGC | 1 |
| Kansino kansino.nl | Play North Ltd | Netherlands | 1 |
| Kanuuna kanuuna.com | Blixx Gaming Ltd | Estonia | 1 |
| Kapow Casino kapowcasino.dk | RoyalCasino | Denmark | 1 |
| Karamba closed karamba.com | Karamba | — | 1 |
| Karl Casino karlcasino.com | L&L Europe | UKGC, Sweden | 1 |
| Kasarmi Casino kasarmi.com | Vana Lauri OÜ | Estonia | 1 |
| Kassu (UK, kassu.com) closed kassu.com | Genesis Global | MGA, UKGC | 1 |
| Kassu (Estonia, kassuuu.com) kassuuu.com | Happy Hour Solutions Limited | Estonia | 1 |
| Kaszino.hu kaszino.hu | LVC Diamond (Las Vegas Casino) | Hungary | 1 |
| Katie's Bingo katiesbingo.com | run by Broadway Gaming Group white label | UKGC | 1 |
| KatsuBet katsubet.com | Scores55 Tech B.V. (mBit / RocketPlay) | Curaçao | 1 |
| KatsuWin katsuwin.ai | Initial Singularity Limited | Anjouan | 1 |
| KBET closed kbet.bet.br | Enseada Serviços e Tecnologia Ltda | Brazil SPA (Ministry of Finance) | 1 |
| Kbet Uganda kbet.ug | Not identified | Uganda | 1 |
| Ken Howells Bookmakers kenhowells.com | Targetlocal Limited (Ken Howells) | UKGC | 1 |
| Kessbet kessbet.com | Not identified | Kenya | 1 |
| Kick kick.com | Easygo (Stake / Kick) | — | 1 |
| Kickr kickr.com | Kickr Games Pty Ltd | — | 1 |
| Kilibet kilibet.ke | Not identified | Kenya | 1 |
| King Billy kingbillycasino.com | Dama N.V. / Novatrix SRL network | Tobique, Anjouan | 1 |
| King Casino (Romania, kingcasino.ro) kingcasino.ro | Winmasters (Level Up Interactive) | Romania, Greece | 1 |
| King Casino (UK, kingcasino.com) kingcasino.com | Jupiter Gaming Limited | UKGC | 1 |
| King Jackpot kingjackpot.co.uk | Broadway Gaming Group | UKGC | 1 |
| King Panda closed kingpanda.bet.br | Seguro Bet Ltda | Brazil SPA (Ministry of Finance) | 1 |
| King.rs king.rs | King.rs | Serbia | 1 |
| Kingdom Casino (kingdomcasino.io) kingdomcasino.io | Softon Ltd (Kingdom Casino, MadCasino) | Anjouan | 1 |
| Kings.game kings.game | Royal Way Limited (Coins.game) | Anjouan | 1 |
| Kingsbet kingsbet.cz | Novomatic AG | Czechia | 1 |
| KingSpin kingspin.co.uk | Happytiger ApS | UKGC | 1 |
| Kingswin (.com) kingswin.com | Befuria GO OÜ | Estonia | 2 |
| Kirolbet kirolbet.es | Grupo Kirol (Kirolbet) | Spain | 1 |
| Kitty Bingo kittybingo.com | The Rank Group Plc | UKGC | 1 |
| Klirr klirr.com | Buccone | Sweden | 1 |
| Klondaika klondaika.lv | Laimz / Klondaika | Latvia | 1 |
| Knight Slots knightslots.com | run by SkillOnNet white label | UKGC, MGA, Sweden | 3 |
| Knucklebet knucklebet.com.au | The Booki Group (Booki.com.au Pty Ltd) | Australia NT Racing and Wagering Commission | 1 |
| KoiCasino koicasino.com | Njord Vantage Services LTD | Estonia | 1 |
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| Kroon Casino krooncasino.com | Betsson AB | — | 1 |
| Kruuna kruuna.com | Njord Vantage Services LTD | Estonia | 1 |
| Kryptosino kryptosino.com | MOONSEEKER SRL | Anjouan | 1 |
| KTO closed kto.bet.br | KTO Group | Brazil SPA (Ministry of Finance) | 1 |
| KukiMuki kukimuki.com | Metaface Limited | Anjouan | 1 |
| Kungaslottet kungaslottet.se | Immense Group (formerly Videoslots) | Sweden | 1 |
| Kwachua (Ken.bet) ken.bet | Not identified | Kenya | 1 |
| kwiff kwiff.com | kwiff | UKGC | 1 |
| Kwikbet kwikbet.co.ke | Not identified | Kenya | 1 |
