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