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Zalo vs imo: catalog facts
Zalo	imo
Free Free to download and use for messaging and calls.	Free Free to download and use.
Windows, macOS, Android, iOS	Windows, macOS, Android, iOS
Widely used in Vietnam, so most contacts there already have it Messaging and calling in one app	Audio and video calls on mobile and desktop Built-in message translation
Official site is mostly in Vietnamese Closed source, run on the developer's servers	Proprietary and closed source Limited technical detail published about its encryption
Downloadable app, Hosted service	Downloadable app
Closed source	Closed source
License not stated	License: Proprietary
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 October 2, 2026

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