CFS Tag Writer

Read, write, clone, and erase CFS filament spool NFC tags on the Flipper.

CFS filament spools identify themselves with a pair of MIFARE Classic 1K NFC tags that store the brand, material, color, weight/length, and serial in an encrypted format. CFS Tag Writer decodes those tags and lets you write them back — clone a spool as-is, edit its fields, build one from scratch, or wipe a tag blank.

The physical tags are standard MIFARE Classic 1K — so you don't need a genuine Creality spool tag. Writing from scratch (or cloning) works onto any writable MIFARE Classic 1K tag, so a blank/generic 1K tag works as the medium.

Compatible with Creality CFS spool tags and any MIFARE Classic 1K tag. "Creality" is used only to describe tag compatibility and the spool brand; this app is not affiliated with or endorsed by Creality.

Features

• Read a tag and view brand, material, color, weight, length, serial, and UID — plus a Raw / Details view showing the decoded 48-byte payload as ASCII + hex. A successful read plays a confirmation sound.
• Write from scratch with a weight-driven wizard (brand → material → color → weight; the weight sets the encoded length). Materials come from the built-in filament catalog, filtered by the selected brand.
• Clone / Edit & Write from a read or saved tag — copy as-is (byte-for-byte), or tweak first.
• x2 dual-tag writing — write both of a spool's tags, with a swap prompt in between.
• Saved Tags — tags are saved as standard Flipper MIFARE Classic .nfc files; open them through the file browser (browse anywhere, including files from the stock NFC app), then re-write, edit, or delete.
• Erase a tag back to blank.
• Settings — default brand, serial mode, editable weight presets, and a crypto/data self-test.

See GUIDE.md for a full step-by-step walkthrough with screenshots.

Documentation

Doc	Covers
GUIDE.md	Step-by-step user walkthrough with screenshots
changelog.md	Per-version release notes
CLAUDE.md	Codebase structure and conventions, for AI-agent or new-contributor onboarding

Safety

Only clone or write tags for spools you own. This app is for managing your own filament.

Screenshots

Read result	Write confirm	Help

More in GUIDE.md.

Building

Built with uFBT:

ufbt            # build the .fap
ufbt launch     # build, install, and run on a connected Flipper

License

MIT © 2026 P. Schattenberg

Support

If this saved you a spool, consider buying me a coffee:

Acknowledgments

Built in collaboration with Claude Code (Anthropic).