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Trelby vs Slugline: catalog facts
Trelby	Slugline
Free Free software under the GPL.	Freemium Free up to six pages per script; longer scripts need the Unlimited Writing upgrade.
Linux	macOS, iOS
Enforces correct screenplay formatting and pagination Imports and exports Final Draft and Fountain files	Automatic screenplay formatting as you type Drag-and-drop outline that moves the matching script text
Interface built with wxPython looks dated next to commercial tools No collaboration or cloud sync features mentioned	Apple platforms only Scripts longer than six pages require a paid upgrade
Downloadable app	Downloadable app
Open source	Closed source
License: GPL-2.0	License not stated
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked October 2, 2026

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