GitHub - swimmingbrain/texbrain: FOSS browser-based latex editor with live preview, real-time collaboration, and git integration.

A free, open-source LaTeX editor that runs entirely in your browser.
No accounts. No installs. No servers. Just open a tab and write.

Try it now → tex.swimmingbrain.dev

I built this because I was tired of paying for features that should be free. I wrote my thesis last year in LaTeX and spent more time fighting tooling than actually writing. Online solutions lock git sync behind a paywall. Local setups break between machines. I wanted something that just works. Open a browser, write LaTeX, get a PDF.

So I built it.

What it does

texbrain is a full LaTeX editor that compiles your .tex files to PDF directly in the browser. There is no backend. No server processing your files. Everything (the editor, the compiler, the git client) runs client-side.

You can open a local project folder, edit your files, see the PDF update, commit your changes, and push to GitHub. All from one tab.

Features

• LaTeX compilation in the browser. Uses a WebAssembly port of pdfTeX (SwiftLaTeX). Your .tex files are compiled to PDF without ever leaving your machine. Packages are loaded on demand and cached locally, so the first compile only downloads what your document actually uses. Recompilations take 1 to 5 seconds depending on project complexity.
• Most of CTAN, loaded on demand. Common packages ship with the app. Anything else (memoir, abntex2, KOMA-Script, you name it) is resolved automatically from a TeX Live mirror the first time a document needs it, then cached locally for offline use.
• Live PDF preview. Rendered with pdf.js. Multi-page, zoomable, with text selection.
• Full git integration. Clone repos, create branches, stage files, commit, push, pull, merge. All powered by isomorphic-git running in the browser. No CLI needed.
• Local file system access. Uses the File System Access API to read and write directly to your project folder on disk (Chrome/Edge).
• Multi-file projects. File tree, tabs, drag-and-drop. Supports .tex, .bib, .sty, .cls and more.
• CodeMirror 6 editor. Syntax highlighting, autocomplete for 70+ LaTeX commands, bracket matching, code folding, snippets, dark/light theme.
• Command palette. Quick access to actions via keyboard shortcut.
• Snippet picker. Math environments, document structures, Greek letters, common commands. Searchable and categorized.
• Works offline. Once loaded, the app works without an internet connection. Compilation is local, editing is local. Packages you've compiled with before are cached; only a package you've never used needs the network once.
• Project templates. Start from scratch or pick a template (article, thesis, beamer, report, CV, letter, minimal).

How it works under the hood

There's no magic and no backend.

Editor. Built on CodeMirror 6 with a custom LaTeX grammar (Lezer parser), autocomplete provider, and theme system. The editor supports multiple open files via tabs and syncs content with both the local filesystem and the in-memory git working tree.

Compiler. LaTeX compilation uses SwiftLaTeX's pdfTeX engine compiled to WebAssembly. The engine runs in a memory filesystem (MEMFS), where your project files are written before each compilation. When the engine asks for a file it doesn't have (a class, package, font, ...), the service worker resolves it through a chain: previously cached files first, then the package subset bundled with the app, then a TeX Live mirror (a texmf-dist mirror on jsDelivr, with a community SwiftLaTeX server as fallback). Every resolved file is stored in the browser's cache storage, so each package is downloaded at most once. After the first successful compile, the bundled subset is also prefetched in the background so the core package set works offline.

Git. All git operations use isomorphic-git, a pure JavaScript implementation of git. The repository lives in an in-memory filesystem (LightningFS) backed by IndexedDB. Your project files are synced between the local filesystem and the git working tree. Remote operations (push/pull/clone) go through a CORS proxy since browsers can't speak the git protocol directly.

PDF viewer. Rendered with pdf.js, Mozilla's PDF rendering library. Supports multi-page rendering with a text layer for selection and search.

File system. The app uses the File System Access API to read/write your actual files on disk. This requires a Chromium-based browser (Chrome, Edge, Arc, Brave). For other browsers, there's a fallback using the Origin Private File System (OPFS).

Frontend. SvelteKit with the static adapter. The entire app is pre-built to static HTML/CSS/JS and deployed to GitHub Pages. No SSR, no API routes, no server. Tailwind CSS handles styling.

Known limitations

• pdfTeX only. No XeTeX or LuaTeX, so fontspec, polyglossia and anything else that needs them won't compile.
• No bibtex or biber. The engine doesn't ship either. Documents using biblatex get a plain thebibliography generated from the .bib file, so references show up but the citation style is ignored. Classic bibtex workflows need a .bbl in the project. A real bibtex in WASM is next on the list.
• TeX Live 2020 era. Packages are pinned to the same era as the engine's format file, so newer package versions aren't available.
• Git remotes need a CORS proxy. Browsers can't speak the git protocol directly. The default proxy is configurable, see below.
• Direct folder access is Chromium only. Firefox and Safari fall back to a virtual filesystem, see Browser support.

Security and privacy

Everything runs in your browser. Your files never leave your machine unless you explicitly push to a remote.

• No telemetry, no analytics, no tracking.
• No accounts, no cookies, no data collection.
• Git authentication tokens are stored in your browser's localStorage. They never touch a server I control.
• LaTeX compilation happens in a WebAssembly sandbox. There are no shell commands being executed. No pdflatex, no exec(), no spawn().
• Git operations use a JavaScript library, not CLI commands. No command injection is possible.
• The CORS proxy for git remotes is a known trade-off. By default it uses cors.isomorphic-git.org (the isomorphic-git project's public proxy). You can point it at your own if you prefer.
• Packages that aren't bundled are fetched from public TeX Live mirrors on demand. Only package filenames are sent, never your document content. Fetched files are cached locally, so this happens once per package. The fallback server can be changed or disabled entirely via the texliveMirror preference (empty string turns it off).
• LaTeX and TeX are free and open-source software. This project uses them. It doesn't redistribute or modify their source.

Tech stack

Layer	Technology
Framework	Svelte 5 + SvelteKit (static adapter)
Editor	CodeMirror 6 + custom LaTeX language support
Compiler	pdfTeX via WebAssembly (SwiftLaTeX)
Git	isomorphic-git + LightningFS
PDF	pdf.js
Styling	Tailwind CSS 4
Language	TypeScript
Deployment	GitHub Pages

Running locally

git clone https://github.com/swimmingbrain/texbrain.git cd texbrain pnpm install pnpm dev

Open http://localhost:5173 in Chrome or Edge.

Browser support

Full functionality requires the File System Access API, which is available in Chromium-based browsers (Chrome, Edge, Arc, Brave, Opera). Firefox and Safari can still use the editor with the virtual filesystem fallback, but won't be able to read/write directly to local folders.

License

MIT

Built by Braian Plaku