I keep my reading habit pretty structured, so when the question is ‘which sites host official translations only,’ I think in terms of three categories: major web-portal publishers, licensed storefronts, and regional apps. Major portal publishers include Webtoon (Naver WEBTOON) and Kakao Webtoon/KakaoPage — those are essentially the official international outlets for many Korean series. They don't mix in fan translations; the content is provided by the creators or their publishers and localized through official channels.
Licensed storefronts like Tappytoon and Lezhin Comics operate slightly differently — many titles are behind paywalls or episode passes, but everything there is licensed and translated officially. Manta has been positioning itself as a licensed-first platform for mobile readers, while Comikey and Bilibili Comics license select titles and provide official translations for their catalogs. Piccoma is another
one to watch, especially for Japanese releases that have licensed translations.
If you want a practical checklist: official-only services will have terms of service that forbid uploaded scans, explicit publisher credits, and monetization (microtransactions, chapter purchases, subscriptions). Also check for links to the publisher or creator pages. I've learned to avoid sites that host both user uploads and official releases, because those often blur the line. For supporting the industry and getting the cleanest, most reliable translations, I default to the platforms I mentioned and it keeps my conscience and library tidy.