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Responsively App vs Sizzy: catalog facts
Responsively App	Sizzy
Free The open-source application is available without a license fee.	Paid A paid subscription is required after the trial.
Windows, macOS, Linux	Windows, macOS, Linux
Interactions mirror across every viewport at once Screenshots every device size in a single action	Project workspaces keep devices, URLs and sessions together Isolated sessions per project avoid cookie collisions between clients
Electron application with a large memory footprint Rendering is Chromium only, so it says nothing about Firefox or Safari	Paid subscription Chromium rendering only
Downloadable app	Downloadable app
Open source	Closed source
License: AGPL-3.0	License not stated
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked September 22, 2026

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