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Responsive Design Checker vs LT Browser: catalog facts
Responsive Design Checker	LT Browser
Free Free to use.	Freemium Free to download, with paid tiers as part of the TestMu AI platform.
Web	Windows, macOS, Linux
Previews several screen sizes from one page Nothing to install	Views several device viewports side by side More than 50 device screen presets
Limited to five requests every five minutes Simulated viewports, not real devices	Device views are emulated rather than real hardware Tied to a commercial testing platform with paid tiers
Web application	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
Needs internet	Not stated if it works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked September 23, 2026

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