Carbon

Free plan AndroidAPILinuxMacSelf-hostedWeb+1

What Carbon is

Carbon is a free workspace combining todo lists, GTD planning, project management, notes, recurring work, time tracking, and offline storage. It supports nested projects, folders, tasks, notes, dependencies, due and defer dates, reminders, recurrence, tags, flags, and priorities. Planning views include Inbox, Today, Flagged, Forecast, Plan, Review, Time, Tags, and Nearby, with saved perspectives, filters, daily time budgets, and project review intervals. Time tracking records sessions, task segments, pauses, edits, and notes, with CSV reports. Rich Markdown notes can contain inline images, comments, and attachments, while databases, attachments, notes, and task checklists support export or import options. Local use needs no account and stores data in SQLite for offline work. Carbon runs on web, Windows, macOS, Linux, and Android. A self-hosted sync server adds shared projects, multiple assignees, permissions, federation, API keys, webhooks, CalDAV, iCal feeds, Home Assistant, Telegram, and configured AI providers. The repository identifies a GPL-3.0 license.

Who it suits

Carbon suits people who want tasks, projects, notes, planning, and time tracking in one system. It also fits users needing local offline work or a self-hosted sync server across supported platforms.

What it does well

Offline local use without an account
Nested projects and task dependencies
Built-in time tracking and CSV reports
Self-hosted sync server option
Web, desktop, and Android support

What to know first

Not end-to-end encrypted
Server operators can read stored workspace data
Uncached attachments require a connection
External integrations require a connection

Verdict

Carbon offers broad planning, documentation, time-tracking, and collaboration features with local storage and self-hosting options. Its lack of end-to-end encryption and connection requirements for some content should shape deployment decisions.

Facts from Carbon's own pages

API: Carbon provides a REST API with personal API keys that can be scoped by permissions and optionally restricted to project subtrees. · github.com, 11 Oct 2026
Authentication: Sync accounts require a password and two-factor authentication through email or an authenticator app; passwords use salted scrypt hashes. · github.com, 11 Oct 2026
Calendar sync: Yes · github.com, 22 Sept 2026
Collaboration: With a sync server, Carbon supports multi-device sync, shared projects and tasks, multiple assignees, read/write permissions and cross-workspace federation. · github.com, 11 Oct 2026
Collaboration and integrations: Sync-server features include shared projects and tasks, multiple assignees, scoped API keys, webhooks, CalDAV and iCal feeds, Home Assistant, Telegram and configured AI providers. · github.com, 11 Oct 2026
Connectivity limits: Uncached attachments and external integrations require a connection, and local reminders depend on app and platform support. · github.com, 11 Oct 2026
Data deletion: Recently Deleted allows restoration for 30 days, while deletion uses tombstones and does not erase records from databases or shrink database files. · github.com, 11 Oct 2026
Data recovery: Recently Deleted allows restoration for 30 days, while deletion hides records using sync tombstones rather than erasing them from databases. · github.com, 11 Oct 2026
Free plan: Yes · github.com, 22 Sept 2026
Integrations: The feature documentation lists CalDAV, iCal feeds, Home Assistant, Telegram, external webhooks and AI task features through a configured provider. · github.com, 11 Oct 2026
License: The public repository identifies its license as GPL-3.0. · github.com, 11 Oct 2026
Local use: Local use needs no account and stores data in SQLite for offline work. · github.com, 11 Oct 2026
Notes and exports: Notes support rich Markdown, inline images, comments and attachments, with database and attachment export/import and Markdown export for notes and checklists. · github.com, 11 Oct 2026
Notes and files: Carbon supports rich Markdown notes, inline images, comments, attachments, database and attachment import/export, and Markdown export for notes and task checklists. · github.com, 11 Oct 2026
Offline access: web_and_mobile · github.com, 22 Sept 2026
Planning: Views include Inbox, Today, Flagged, Forecast, Plan, Review, Time, Tags and Nearby, with saved perspectives, filters, daily time budgets and project review intervals. · github.com, 11 Oct 2026
Planning features: It includes nested projects and tasks, due and defer dates, reminders, recurrence, task dependencies, priorities and saved views. · github.com, 11 Oct 2026
Platforms: The project documents a web/PWA, desktop and Android app; its desktop app uses Tauri and Android uses Capacitor. · github.com, 11 Oct 2026
Product: Carbon combines task management, projects, notes, recurring tasks, time tracking and offline storage. · github.com, 11 Oct 2026
Purpose: Carbon combines todo, GTD, project management and time tracking, with local storage, sharing and APIs on a self-hostable sync server. · github.com, 11 Oct 2026
Recurring tasks: Yes · github.com, 22 Sept 2026
Security: Carbon is not end-to-end encrypted, and server operators can read stored workspace data, including integration credentials. · github.com, 11 Oct 2026
Security limitation: Carbon is not end-to-end encrypted, and server operators can read stored workspace data, including integration credentials. · github.com, 11 Oct 2026
Self-hosting: The self-hosted server serves the app and API on port 3069 and stores data in a local data directory; remote access should use HTTPS. · github.com, 11 Oct 2026

Where Carbon stands on Freedom251

To-do list apps#54 of 150