Documentation

Mermaid91.0k★

Mermaid turns plain text into diagrams: flowcharts, sequence diagrams, ER diagrams, Gantt charts, plus newer types like architecture diagrams, kanban boards and Wardley maps. It's MIT, and GitHub, GitLab, Obsidian and Notion render it natively, so a code block in a README becomes a picture with no image file to keep in sync. Cost to run: zero. Drop the library into a page, or do nothing when your platform already renders it. Version 12 (September 2026) made ELK the default layout engine, which re-lays out existing flowcharts; set layout: dagre to keep the old layout. The paid side is Mermaid Chart at mermaid.ai, a hosted editor with AI credits, billed annually only. Plus is $10 per user per month, Premium $20, and SSO now lives in custom-priced Enterprise. Solo and small teams: free library, skip the editor. Larger teams pay only when non-technical people want a visual editor or SSO. The catch: you steer the layout, you don't place nodes, so big diagrams need restructuring when the engine guesses wrong. For polished presentation work, Excalidraw wins. Rendering diagrams from untrusted users? Stay current: 2026 brought nine medium and low severity advisories.

AppFlowy78.3k★

AppFlowy is the closest open source thing to Notion: docs, wikis and databases with grid, kanban, calendar, timeline and chart views, plus formulas and AI, in native desktop and mobile apps. The apps are AGPL-3.0, and the desktop app runs completely offline for free. Self-hosting changed in 2026. The original AGPL server is archived; the maintained server is a closed-source commercial fork shipped as a dozen Docker containers. Its free tier gives one user seat per instance, three guest editors and web access only. Desktop and mobile apps need a paid plan. The free cloud plan is a one-owner workspace with 100MB of storage. Pro is $12 per member a month billed annually, $16 monthly. Self-hosted One is $6 a month and Team is $10 per seat a month, annual only. Solo: free desktop app. Small teams: Cloud Pro. Larger teams: self-hosted Team, up to 1,000 seats with SCIM and LDAP. The catch: AppFlowy now calls itself open-core. Every release since 0.13.0 is tagged to the same June 2026 commit, so downloads aren't built from public source. The old open source server has unpatched 2026 CVEs, including one that lets a logged-in user read other workspaces' documents.

Docusaurus66.7k★

Docusaurus turns a folder of Markdown into a full documentation site: versioned docs, a blog, search, translations and a sidebar built from your files, all output as static HTML you can host anywhere. Meta built it for its own open source projects, and it runs the React Native and Jest sites. MIT licensed and completely free. npm init docusaurus@latest gets you a working site, and Vercel, Netlify or GitHub Pages will host it. Pages are MDX, so you can drop React components straight into the docs. Search is Algolia DocSearch, free for developer docs, or a community local-search plugin if you'd rather skip Algolia. Builds used to be slow; the Rspack-based Docusaurus Faster work in 3.6 made them two to four times quicker. No paid tier exists: solo devs through large teams pay only for hosting. The catch: it's a React app wearing a docs costume. Customizing past the theme means writing React, and there's no web editor, so non-technical writers either learn Git or you move to a hosted platform like Mintlify or GitBook. Version 4 is in canary with breaking changes and a Node 24 floor, so budget an upgrade. Simple sites fit VitePress or MkDocs better.

outline41.2k★

Outline is a team wiki built on React and Node.js that actually feels like a modern writing tool. Real-time collaboration, slash commands, markdown support, nested collections, and deep integrations with Slack, Figma, and 20+ other services. The editor is fast and clean, closer to Notion than Confluence. Search works well. Permissions are granular enough for real teams. API and webhooks let you build on top of it. Self-hosting gives you full control over your data, which matters when your wiki holds internal strategy docs and onboarding playbooks. The alternatives here are Notion (polished but closed), Confluence (enterprise bloat), and BookStack (simpler, fully open). Outline sits in the middle: more capable than BookStack, less locked-in than Notion. The BSL license means you cannot offer it as a hosted service to others. The catch: self-hosting requires Postgres, Redis, and S3-compatible storage, not a one-click setup. And the cloud pricing starts at $10/month but jumps to $79/month once you pass 10 users.

docsify31.6k★

Docsify serves your .md files directly in the browser. Drop an index.html file in your docs folder, push to GitHub Pages, done. Your Markdown becomes a website in minutes. Everything is free under MIT. No paid tier, no cloud service, no premium themes. Well-established with a solid plugin ecosystem. It's been around since 2016 and the community keeps it maintained. There's nothing to build or host in the traditional sense. Docsify loads a single JavaScript file that fetches your Markdown files at runtime and renders them in the browser. Host it on GitHub Pages ($0), Netlify ($0), or any static file server. The "deployment" is copying files. Solo developers: this is the fastest path from Markdown to docs website. If you already have docs in a GitHub repo, you can have a site live in 5 minutes. Small teams: great for internal docs, project wikis, runbooks. Growing teams: it works, but no build step means no type checking, no broken link detection at build time. The catch: because there's no build step, Docsify has worse SEO than static site generators. Search engines see a blank page until JavaScript loads and fetches the content. If public discoverability matters, use VitePress or Docusaurus instead. For internal docs where SEO doesn't matter, Docsify is perfect.

Swagger UI29.1k★

Swagger UI turns your OpenAPI spec into a live, interactive documentation page where anyone can try your API without writing code. Paste a spec file, get a browsable, testable doc site. This is the standard. Apache 2.0, used by basically every team that documents APIs. You drop it into your project, point it at your OpenAPI JSON or YAML, and your docs are live. It renders every endpoint, shows request/response schemas, and lets users hit your API right from the browser. The free version does everything most teams need. SmartBear (the company behind Swagger) sells SwaggerHub for hosted collaboration, versioning, and team management starting around $75/mo per user, but that's the platform, not the UI component. The open source UI itself has zero paywalls. The catch: it only works with OpenAPI specs. If your API isn't documented in that format, you need to write the spec first (or use a code-first tool that generates it). And the default styling looks like 2018. Functional, not pretty. Redoc looks better out of the box if aesthetics matter to you.

Redoc26.0k★

Redoc turns your OpenAPI spec into readable API documentation in one command. Drop in your spec file, get a fully rendered docs page with a three-panel layout: navigation, content, and code samples. The output is clean. Seriously clean. Better-looking than Swagger UI out of the box. It renders as a single HTML file, no server needed. Host it on GitHub Pages, Netlify, S3, or embed it in your existing site. One of the most popular API documentation generators. Used by companies from startups to enterprises. Redoc itself is free and MIT licensed. The commercial product is Redocly (the platform), which adds API linting, versioning, developer portals, and team collaboration, starting at $69/mo per project. The catch: Redoc only reads OpenAPI specs. If your API isn't documented in OpenAPI format, Redoc can't help you. It's also read-only, no "Try it" button for sending test requests like Swagger UI has. If interactive testing matters, Swagger UI or Stoplight Elements are better fits. But for pure documentation quality, Redoc wins.

MDX19.9k★

MDX is Markdown with JSX superpowers. Write normal Markdown, and when you need something dynamic, import a React component and use it inline. That's the whole pitch. MIT licensed, used by Docusaurus, Next.js docs, Gatsby, and half the documentation sites on the internet. It's the standard for component-enhanced content. Fully free. No paid tier, no hosted service. It's a compiler that transforms your .mdx files into JavaScript. Works with every major framework: React, Vue (via plugins), Svelte, and more. The catch: MDX adds build complexity. Your content now depends on a JavaScript build pipeline. You can't just render Markdown server-side anymore. Debugging MDX compilation errors is painful, especially when you mix complex JSX with Markdown. And if your content team isn't comfortable with JSX syntax, they'll hate it. For pure Markdown with no interactivity, stick with regular .md files.

BookStack19.1k★

BookStack organizes documentation into a hierarchy that actually makes sense: shelves hold books, books hold chapters, chapters hold pages. It is a wiki built for people who think in structure, not chaos. The WYSIWYG editor works out of the box, no markdown gatekeeping required. Role-based permissions let you lock down who sees what, which matters once your team grows past five people. Multi-factor auth, audit logging, LDAP and SAML support ship built in. Diagrams.net integration, API access, and full-text search round it out. If you have tried Notion or Confluence and wanted something you actually own, this is the answer. GitBook gives you hosted convenience but locks your docs behind their platform. Outline looks slicker but needs more infrastructure to run. Wiki.js is the other serious self-hosted option but feels more generic. The catch: it is PHP and Laravel, so you need a traditional LAMP-style server. No official hosted version exists. You run it or you do not use it.

scalar16.4k★

Scalar turns an OpenAPI file (the machine-readable spec of your API's endpoints) into a clean, interactive reference page where readers can send real requests. It also ships an offline-first API client for Windows, macOS and Linux that its own README calls a Postman alternative. Both are MIT licensed and free. Setup is light. One HTML file loading it from a CDN, a plugin for your framework (FastAPI, Express, ASP.NET Core, Laravel and dozens more), or docker run scalarapi/api-reference. Elysia, Litestar and Nitro ship it as their default docs UI. Nothing to babysit. The paywall is the hosted platform. Free covers hosted docs for 3 APIs and 1 editor seat. Pro is $150/month ($1,500/year) for custom domains, Git Sync and 5 editors; Business is $600/month ($6,000/year) for SSO and 10 editors. Solo and small teams: free. Teams pricing out ReadMe or SwaggerHub: Pro, or Business once you need SSO. The catch: the quickstart routes those requests through proxy.scalar.com, which carries your auth headers, and in September it patched a bug that forwarded credentials across redirects. That's one of eleven advisories since early September, including a critical code-execution bug in the mock server. Run your own proxy and stay current.

md13.5k★

Publishing to WeChat means pasting into an editor that mangles your formatting, and doocs/md exists because that experience is miserable. Write Markdown on the left, watch WeChat-ready styled output appear on the right, then copy it into the official editor with the formatting intact. It is released under the WTFPL, about as permissive as licensing gets. The feature list runs well past its original job. KaTeX math, Mermaid and PlantUML diagrams, custom CSS themes, local draft autosave, and image upload to whichever host you already pay for: GitHub, S3, Cloudflare R2, MinIO, Aliyun, Tencent, or Qiniu. Self-hosting is one Docker command or a global npm install, and there is a Chrome extension build if you would rather it live in the browser. Writers and small content teams get everything for nothing at md.doocs.org with no account required. Sign in only if you want editor preferences synced across devices. The AI assist features route through DeepSeek, OpenAI, Qwen, and others on your own API key. The catch is the audience. Everything is built around WeChat's rendering quirks, the docs and issues are primarily in Chinese, and outside that publishing channel most of the value evaporates.

Markdoc8.5k★

Built by Stripe for their docs (stripe.com/docs runs on it), then open-sourced. Everything is free under MIT. No paid tier, no cloud service. It's a parsing library you integrate into your build pipeline. Stripe maintains it alongside their docs infrastructure. There's nothing to host. Markdoc is a library that transforms .md files into a renderable tree. Plug it into Next.js, React, or any framework. The source files are still readable Markdown. The custom tags look like {% callout %} rather than <Component>, which means non-developers can still edit the docs. Solo developers: if standard Markdown works, you don't need this. Use it when you need variables ({% $version %}) or conditional rendering in docs. Small teams: great for maintaining docs with reusable components: define a callout once, use it everywhere. Growing teams: this is built for docs at scale. The catch: smaller community than MDX. If you want React components directly in Markdown, MDX has a bigger ecosystem. Markdoc's advantage is that source files stay readable as plain text. MDX files are basically JSX with Markdown mixed in.

codebase-to-course5.8k★

This Claude Code skill turns any repository into a beautiful, interactive single-page HTML course. Point it at a codebase, and it generates a structured learning experience that walks through the architecture, key files, and how everything connects. Built specifically for non-technical 'vibe coders' who learn by doing and want to understand what they built (or what someone else built). The output is a single HTML file you can share, host, or open locally. No language specified in the repo. It's a Claude Code skill file, not a traditional software project. The catch: the quality depends entirely on Claude's understanding of the codebase. Complex, poorly-documented codebases will produce courses with gaps. And 'single-page HTML' means everything is in one file. Great for sharing, awkward for very large codebases. This is a skill, not a product. It runs inside Claude Code only.

markdown-online-editor4.0k★

Arya (the repo is markdown-online-editor) handles the Markdown things most editors punt on: flowcharts, Gantt charts, sequence diagrams, ECharts graphs, and sheet music, all from fenced code blocks. Paste HTML and it converts to Markdown on the way in. Flip a setting and Reveal.js turns the document into a slide deck. Export lands as PDF, PNG, JPEG, or Word. MIT, and the hosted version is free with no account. Self-hosting is about as easy as it gets, because there is no backend. It is a static build, so a Docker image, Cloudflare Pages, or GitHub Pages all work, and the Docker route is a single command. Documents live in the browser's local storage, which means nothing leaves your machine and also that there is no sync. Solo writers and note-takers: free either way, hosted or self-hosted. Teams: this is a single-player editor with no collaboration, so pair it with something else for shared docs. The catch: it is built on Vue 2, and the build still pins Node to 16 or 17 and needs the openssl-legacy-provider flag to compile. It is actively maintained, but you are running a frontend on a framework the ecosystem moved past. The interface is also Chinese only, with no translation layer in the codebase.

md-editor-v32.6k★

Md-editor-v3 gives you a split-pane editor with preview, toolbar, and syntax highlighting out of the box. Drop it into your Vue app and you have a working editor in minutes. MIT license, TypeScript. Features include live preview, table editing, code block syntax highlighting, emoji picker, image upload hooks, Mermaid diagram support, KaTeX math rendering, and customizable toolbars. Also supports React via a companion library (md-editor-rt). Dark mode included. Fully free. No paid tier, no premium features. Everything (all toolbar options, all rendering modes, all plugins) is included. Solo to large teams: free. It's a component library, not a service. Your only decision is whether it fits your needs. The catch: this is a Vue-first library. The React port exists but has fewer stars and less community attention. If you're on React, there are more mature options (Tiptap, Milkdown, react-md-editor). Also, the documentation is partially in Chinese; the English docs are functional but not comprehensive. If you hit an edge case, you might be reading source code.

rspress2.4k★

Rspress is a static site generator built on Rust-powered tooling (Rspack) that compiles your Markdown into a blazing-fast React site. It's Docusaurus but with build times that don't make you reconsider your career. It uses MDX, supports full-text search out of the box, has i18n, and generates an optimized site with automatic code splitting. The developer experience is solid: hot reload is near-instant because Rspack (the Rust bundler underneath) handles the heavy lifting. MIT. Fully free. No paid tier, no cloud service, no account. Build your docs site and deploy it wherever you want. The catch: it's emerging. The ecosystem is tiny compared to Docusaurus . Fewer themes, fewer plugins, fewer community answers when you get stuck. If you need extensive customization beyond what ships out of the box, you're on your own. And the ByteDance backing (web-infra-dev) means long-term governance isn't community-driven.

llm-wiki-compiler2.2k★

llm-wiki-compiler turns a pile of raw sources into a clean, interlinked wiki you can browse and search. Feed it markdown, URLs, PDFs, images, even AI chat transcripts, and it runs an LLM pipeline to compile typed pages with wikilinks and citations that point back to the exact source lines. It's MIT licensed, and you bring your own LLM key. It's a Node CLI, so setup is light: install it, point it at your sources, run compile. The engineering touches are what stand out. It does hybrid semantic and keyword retrieval, tracks changes by hash so re-compiles are incremental, scores the result's health and citation coverage, and ships a read-only local viewer plus an MCP server for Claude or Cursor. You can run it free against a local Ollama model or pay per token with Claude or GPT. There's no clean commercial equivalent. Hosted tools like Mintlify, GitBook AI, and Notion AI live in the same neighborhood, but they're managed docs platforms, not a local compiler that turns arbitrary sources into a cited wiki. Solo builders and small teams drowning in scattered notes and docs: this is worth a real try. The catch: the author calls it early software, and it shows in the edges. Quality depends on the model and its citation judgments, every recompile costs LLM tokens unless you run local, and the viewer is read-only with no freshness watchdog yet.

blume1.8k★

Blume turns a folder of Markdown files into a full docs website: navigation, search, themes, API reference pages, social images, and an llms.txt so AI tools can read your docs too. It's MIT licensed and there's no paid version. The pricing page literally says "Blume is free." Run npx blume init, write Markdown, build, and you get static files you can drop on Vercel, Netlify, Cloudflare Pages, GitHub Pages or any CDN. Under the hood it generates a hidden Astro project, and npx blume eject hands that project to you when you outgrow the defaults. Search runs locally with Orama, so there's no Algolia bill. The optional AI assistant and MCP server need a server deployment and your own model API key. This is the free answer to Mintlify, whose Pro plan runs $450 a month. Solo devs and small teams that write docs in Git get most of what Mintlify sells. Teams with non-technical writers should look harder, because there's no web editor. Docusaurus (facebook/docusaurus) is the safe, boring default; Fumadocs and Starlight are the closest newer options. The catch: one main maintainer, launched in mid-2026 and already on version 2, so expect breaking config changes. Turn on the assistant and you own the token bill and the rate limiting.

retype1.3k★

Documentation lives in Markdown files, and something still has to turn them into a website. Retype does that. Point it at a folder of .md files and it generates a searchable, themed site with navigation, syntax highlighting, and a table of contents. Basically, it's "Markdown in, website out." The free tier lets you build a site with up to 100 pages. That covers most small projects. Beyond that, Pro is $149/project or Business is $249/project (one-time, not subscription). The source code is visible on GitHub but the license is proprietary, not open source despite being on GitHub. There's no cloud hosting from Retype: it generates static files you deploy anywhere: GitHub Pages, Netlify, Vercel, your own server. The build step runs locally or in CI. Solo developers: the free tier works for personal projects and small docs sites. Small teams: 100 pages is tighter than you think; once you add API references and guides, you hit it. The $149 one-time cost is reasonable. Growing teams: Business tier adds custom domains for docs, priority support. The catch: it's not open source. The source is on GitHub for transparency, but the license restricts modification and redistribution. If that matters to you philosophically, Docusaurus or VitePress are fully open source alternatives that do the same thing with more setup.

xwiki-platform1.3k★

XWiki is the heavyweight open source answer to Confluence: a full company wiki with a WYSIWYG editor, realtime co-editing, nested pages, sub-wikis and fine-grained permissions. App Within Minutes lets non-developers build small structured apps, forms plus tables, inside the wiki. The platform is LGPL and free to self-host with no user cap. Self-hosting means Java: Tomcat or Jetty plus PostgreSQL, MySQL or MariaDB, or the official Docker image with those combos prebuilt. Versions ship monthly; run the previous cycle's stable line (17.10.x), which XWiki recommends for production, and patch promptly. It's more work than BookStack or Wiki.js, and does far more. XWiki SAS sells support plus Pro apps, same price cloud or on-prem. Starter is about $346 a year for 10 users, XWiki Cloud only, capped at 25. Basic, about $1,665 a year for 25 users, adds the Pro apps (diagrams, forum, Office 365 and Google connectors). Solo and small teams: free. Big orgs leaving Confluence: Business, from about $12,560 a year for 250 users. The catch: Pro apps are priced by your wiki's total active users, so ten diagram users in a 500-person wiki pay the 500 tier. Confluence macro compatibility is the paid Pro Macros package.

docs727★

This is the documentation site for Prometheus, not Prometheus itself. If you're looking for the monitoring system, you want prometheus/prometheus. This repo contains the source files for prometheus.io, the website that explains how to use Prometheus. That said, if you're contributing to Prometheus documentation or want to run the docs site locally for reference, this is what you'd clone. It's built with Hugo and TypeScript, hosted at prometheus.io. The catch: this is a documentation repo with . It's not a tool you deploy or use in production. If you ended up here looking for the actual monitoring system, head to prometheus/prometheus, that's the 56K-star project you want.