Open source

Open code, data, or methods that support learning, reuse, and remixing.

277 curated websites

Academic Research

1 websites

DeepSeekAI assistant from Hangzhou-based DeepSeek, free to use on web and mobile after sign-up, with DeepThink reasoning and web search; model weights are open-licensed and the API is low-cost.

Online Learning

7 websites

ScratchA free block-based coding platform created at the MIT Media Lab and now run by the nonprofit Scratch Foundation. Build games, animations, and stories in the browser and share them with a global creative community.

MonkeytypeA free, open-source typing test and practice website known for its minimal design and unusually deep customization, with multiple test modes, hundreds of language word lists, and optional accounts for tracking progress.

freeCodeCampA donor-supported nonprofit offering free interactive coding courses, project-based certifications, a tech publication and a community forum — all content and certificates free.

ExercismA free, ad-free coding practice and mentoring platform with 83 language tracks and 8,600+ exercises. Solve in the browser or via CLI, get automated analysis, and request free mentor feedback. Run by a UK not-for-profit; account required.

Seeing TheoryA visual introduction to probability and statistics by a Brown University student team: six interactive D3.js chapters, 2018 Webby winner, in English, Chinese and Spanish. Free, now archived.

The Book of ShadersA free online introduction to fragment shaders with live editable code examples, from basics to generative design and ray marching. In 14 languages including Chinese, developed on GitHub.

Explorable ExplanationsThe hub of the explorable explanations movement: a community-maintained directory of hundreds of learn-through-play web experiences, browsable by subject. Free, CC0 open source, English.

Practical Tools

13 websites

PairDropOpen-source, browser-based file transfer: devices on the same network discover each other automatically and send files peer-to-peer over WebRTC; pairing and temporary rooms extend transfers across networks. No signup, no installation.

Open Food FactsA crowdsourced food database where a barcode scan returns ingredient lists, nutrition tables and Nutri-Score style ratings; everything is published under the ODbL license by a French nonprofit.

Zen BrowserA free, open-source Firefox-based desktop browser (MPL-2.0) maintained by a volunteer community. Built around vertical tabs, with Workspaces, Compact Mode, Split View and Glance; no telemetry; funded by donations. Still officially beta.

AFFiNEAFFiNE is an open-source, local-first workspace fusing block-based docs, an edgeless whiteboard, databases and AI on one canvas, with cloud sync, desktop and mobile apps, and Docker self-hosting — an open alternative to Notion and Miro.

LogseqLogseq is an open-source, privacy-first outliner and knowledge tool that stores notes as local Markdown or Org-mode plain text, with desktop and mobile apps. The app is free (AGPL-3.0); encrypted official sync is an optional paid add-on.

AppFlowyAppFlowy is an AGPL-3.0 open-source Notion alternative built with Flutter and Rust, offering docs, multi-view databases, kanban project management and AI features across local offline workspaces, hosted cloud, and Docker self-hosting.

Cal.comCal.com is a scheduling platform: free booking links for individuals, routing forms and workflows for teams, APIs and embeds for developers. The commercial product went closed source in 2026; the code lives on as MIT-licensed Cal.diy.

DubDub is an open-source link attribution platform combining branded short links, click-to-conversion analytics, affiliate program management, and a developer API — a self-hostable, modern alternative to Bitly and Short.io.

TwentyTwenty is an open-source CRM positioned as an open alternative to Salesforce: customizable data model, email/calendar sync, kanban pipelines, workflows and AI agents, with REST/GraphQL APIs and MCP server, on cloud or self-hosted Docker.

PlanePlane is an AGPL-3.0 open-source project management platform positioned as an alternative to Jira and Linear — work items, cycles, modules, multiple layouts, wiki and AI in one workspace, on hosted cloud, self-hosted Docker, or air-gapped.

DocumensoDocumenso is an AGPL-3.0 open-source e-signature platform positioned as the open DocuSign alternative — documents, templates, teams, API/webhooks and embedded signing — self-hosted via Docker or hosted cloud with a 5-per-month free tier.

FormbricksFormbricks is an open-source survey platform from Germany focused on targeted micro-surveys inside websites and apps. The AGPLv3 core is fully self-hostable; the hosted cloud has a free tier and stores data in Germany.

PostizPostiz is an AGPL-3.0 open-source social media scheduling platform with cross-posting to 30+ networks, a visual calendar and team workflows, plus an MCP server, CLI and API for AI agents; hosted cloud from $29/month or free self-hosting.

Creative Tools

5 websites

ExcalidrawAn open-source virtual whiteboard with a hand-drawn feel — sketch diagrams for free without signing up, with real-time collaboration and end-to-end encryption.

TypstTypst is a markup-based typesetting system and collaborative online editor from a Berlin team, matching LaTeX's power with simpler syntax, instant preview, and helpful errors; the compiler is open source under Apache-2.0.

Google FontsGoogle's free, open-source font library, launched in 2010: 1,946 font families as of 2026-09-02 under libre licenses, free for commercial use via embedding, download, or self-hosting, plus 3,900+ Material Symbols icons.

tldrawA free online whiteboard that works the moment you open it: infinite canvas, hand-drawn strokes, no account needed, saved in the browser. It also showcases the source-available tldraw SDK behind ClickUp Whiteboards and other products.

RiveRive is an interactive animation platform: a web editor for design, animation and state-machine logic, plus MIT open-source runtimes playing .riv files on iOS, Android, web, Flutter, Unity, Unreal. Free editor; exports from $9/seat/month.

Explore the World

2 websites

OpenStreetMapOpenStreetMap (OSM) is a free, editable map of the world built by volunteers, with all data published under the open ODbL license. The official site is a reference map, a search and routing tool, and the gateway to the data.

WikivoyageFree, volunteer-written travel guide hosted by the Wikimedia Foundation, covering destinations, itineraries, and phrasebooks anyone can edit. Forked from Wikitravel in 2006, a Wikimedia project since 2013, in 27 language editions.

Developer Tools

12 websites

IT ToolsAn open-source, free collection of 86 online tools for developers and IT professionals: hashing, encoding, format conversion and network calculators, all running in the browser. No signup; self-hostable via one Docker command.

GitHubThe largest code-hosting and collaboration platform, launched in April 2008 and a Microsoft subsidiary since 2018; as of 2026-09-02 it serves 225M+ developers and 800M+ repositories, with free repos plus Actions and Copilot.

RSSHubAn open-source RSS generator created by DIYgod in 2018 that turns websites without native feeds into standard RSS sources; the code is on GitHub under AGPL-3.0, with an official demo instance and encouragement to self-host.

MDN Web DocsFree, open-source web platform documentation maintained by Mozilla: HTML, CSS, JavaScript, Web APIs, and HTTP, with per-page browser compatibility tables. Online since 2005, edited on GitHub with Open Web Docs and volunteers.

roadmap.shA community-maintained collection of developer learning roadmaps: 80+ career and technology paths as clickable skill trees, each node pairing a brief with curated links; free, with content updates flowing through a public GitHub repository.

WarpWarp is an open-source, Rust-based agentic development environment: a GPU-accelerated terminal with built-in AI coding agents and a code editor for macOS, Windows, and Linux. The terminal is free, no account needed; agents use credits.

SupabaseSupabase is an open-source Postgres backend platform (BaaS): a full database with auto REST/GraphQL APIs, plus auth, storage, realtime, edge functions, and vector search. Free tier; Pro from $25/org/month; Apache-2.0, self-hostable.

ZedZed is a fast, open-source code editor in Rust from Zed Industries, founded in 2021 by the creators of Atom and Tree-sitter. Built for speed, real-time multiplayer collaboration, and model-agnostic AI. Free editor; hosted AI from $10/month.

PlausibleOpen-source, privacy-first web analytics from Estonia's Plausible Insights — no cookies, no personal data, a lightweight script, pageview-based pricing, and a free self-hosted edition.

Learn Git BranchingAn open-source browser app for learning Git visually: ~34 levels plus a free sandbox, with a commit tree that animates as you type real commands. MIT-licensed, in Simplified and Traditional Chinese.

OllamaDownload and run open-weight LLMs such as Qwen, DeepSeek, GLM, and Gemma on macOS, Windows, and Linux, with a desktop app, CLI, and local OpenAI-compatible API. Local usage is free; cloud models are billed per token.

GhosttyGhostty is a free, open-source terminal emulator pairing GPU-accelerated rendering with platform-native UI on macOS and Linux. Started by HashiCorp co-founder Mitchell Hashimoto, written mainly in Zig, MIT licensed.

Fun & Games

3 websites

Online-Go.com (OGS)A free online Go (baduk) server in the browser: real-time and correspondence games, spectating and game study, roughly 59,000 user-made tsumego puzzles, an interactive beginner course and tournaments, with an AGPL-licensed web client.

LichessA free, ad-free, open-source online chess platform with games at every time control, 8 variants, tactical puzzles, engine analysis, tournament broadcasts and collaborative study tools, run by a French non-profit association.

MusicBrainzAn open music encyclopedia run by the nonprofit MetaBrainz Foundation — a volunteer-maintained structured music metadata database whose core data is public domain (CC0), with a free API, full data downloads, and the Picard tagging app.

Cultural Heritage

1 websites

Standard EbooksVolunteer-driven project producing carefully typeset, proofread public domain ebooks from Project Gutenberg transcriptions with public domain cover art; every title is free in epub, azw3, and kepub, dedicated to the public domain.

Science Exploration

1 websites

Stellarium WebThe browser-based edition of the open-source Stellarium planetarium: nothing to install, just open a page to see a real-time sky for any time and place, with planets, constellations, deep-sky objects, and upcoming celestial events.

Health & Living

1 websites

MeditoMedito is a non-profit meditation app from the Netherlands: hundreds of guided meditations, sleep stories, courses and breathing exercises, all free with no ads and no account — and the code is open source. 4.1M users in 190+ countries.

Career Development

1 websites

Reactive ResumeA free, open-source (MIT) resume builder with no ads or tracking, offering 15 templates, 55 interface languages, an in-browser ATS checker, and job application tracking; self-hostable with Docker, AI features require your own API key.

Design Inspiration

1 websites

Stack SortedA free web design inspiration library created in July 2023 by design YouTuber Juxtopposed. It catalogs specific UI elements — buttons, cards, hover effects — from real websites, some with CodePen links. Submissions via form or GitHub PRs.

Website Builders

1 websites

YcodeA visual website builder and CMS by Ycode, Inc., open-sourced under MIT in 2026. Self-host the full feature set free on Vercel + Supabase, or pay per project for Ycode Cloud. Built-in database, multilingual sites, forms and a BYOK AI agent.

Personal Finance

3 websites

Sure (formerly Maybe)Open-source personal finance app: aggregates bank, investment, crypto and property accounts to track net worth, transactions and budgets; self-hostable via Docker. Born as Maybe (2021), open-sourced 2024, now a community fork.

Actual BudgetOpen-source (MIT), local-first budgeting app built on envelope (zero-based) budgeting: data stays on your devices and works offline; optional self-hosted sync and bank imports via SimpleFIN and others. Free since 2022.

GhostfolioPrivacy-first, open source portfolio tracker: record stocks, ETFs and crypto across platforms to see net worth, performance and allocation, with X-ray analysis and FIRE calculator. AGPL-3.0, self-hostable; cloud Premium $48/yr.