Write tabs together. Cotabs is a collaborative tablature editor — Guitar Pro–style notation, real-time multi-user editing, and playback right in the browser.

Features · Quick start · Stack · Architecture · License

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Status — active WIP. Real-time collaborative editing, Guitar Pro import and in-browser playback work today. Export (.gp / PDF), version history and inline comments are not implemented yet. No automated test suite yet either.

Overview

Cotabs brings the feel of a desktop tab editor to a shared browser tab. Open a song, invite your band, and edit the same score at the same time — every fret, hammer-on, and palm-mute syncs live. Import your .gp files, hear them back with a real SoundFont, and never email a project file again.

_{The editor · multi-track tablature with a full notation palette — durations, techniques, dynamics and bar tools.}

Features

• Real-time collaboration — multiple editors on one score, with live cursors and presence.
• Guitar Pro–style notation — bends, slides, hammer-ons, palm mutes, let-ring, tied notes and more.
• Multi-instrument tracks — guitars, bass and a dedicated step-grid drum editor.
• In-browser playback — swappable General-MIDI SoundFonts, count-in, looping and speed control.
• Import Guitar Pro — drop in a .gp file and start editing immediately.
• Share & invite — role-based invitations (editor / viewer) by link.
• Spanish-first, bilingual — neutral Spanish by default, English ready.

Live collaboration — see who's editing where, in real time.	Drum editor — program kits on a per-piece step grid.
Playback SoundFonts — pick a GM bank, or layer one on top for better tones.	Invitations — join a song to collaborate, with an assigned role.

_{Your songs · create a new piece or keep editing an existing one.}

Quick start (dev)

Copy the env template, then bring up the dev stack — the images install dependencies from the committed lockfiles (go.sum, pnpm-lock.yaml) on build:

cp .env.example .env
docker compose -f compose.yml up

Playback banks (optional). The SoundFont binaries (~107 MB) are not committed. Fetch them once for full-quality playback — otherwise Cotabs falls back to a small built-in CDN bank:

./frontend/public/soundfonts/fetch-soundfonts.sh

Service	URL / Address
Frontend	http://localhost:21173
API	http://localhost:21080
Postgres	localhost:21432 — user/pass tabeditor / devpassword
Redis	localhost:21379

Stack

Layer	Technologies
Backend	Go 1.23 · chi · gorilla/websocket · pgx · redis
Frontend	React 18 · Vite · Yjs · alphaTab · Zustand
Infra	Postgres 16 · Redis 7 · Nginx

More on architecture, roadmap and the data model: see PLAN.md. Guidance for Claude Code: see CLAUDE.md.

License

PolyForm Noncommercial License 1.0.0 — see LICENSE.

Source-available and free for any noncommercial purpose (personal use, study, hobby, education, nonprofits, government). Commercial use — including selling the software, charging for access, or using it for profit — is not permitted. This is intentionally not an OSI "open source" license: the OSI definition forbids restricting commercial use, which is exactly what this license does. For a commercial license, contact the author.

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_{Cotabs · made for people who'd rather be playing.}