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Zalo vs Viber: catalog facts
Zalo	Viber
Free Free to download and use for messaging and calls.	Free Free to download and use for messages and calls.
Windows, macOS, Android, iOS	Android
Widely used in Vietnam, so most contacts there already have it Messaging and calling in one app	Voice and video calls plus group chats Chats sync between mobile and desktop
Official site is mostly in Vietnamese Closed source, run on the developer's servers	Proprietary and centrally run Communities and stickers add clutter for people who only want chat
Downloadable app, Hosted service	Downloadable app
Closed source	Closed source
License not stated	License not stated
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Needs internet
Official website Full listing and sources Checked September 24, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.