Reactive – Markdown to interactive web apps, running in-browser
Reactive compiles Markdown files into interactive web apps with forms, live data, real Python, and charts, entirely in your browser. No server, account, or build step required. It's git-friendly, self-hostable, and offers encrypted sync, a local AI assistant, and privacy-by-construction design.
One Markdown file. A working app.
Reactive compiles a Markdown file into a working app — forms, live data, real Python and charts — entirely in your browser. Git-friendly, self-hostable, no lock-in. No server, no account, no build step.
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Built for people who'd rather write a file than run a service
Every card is a real, working app. Click one — it opens in your browser, data and all, nothing to install or sign up for. Then read the source: it's a few lines of Markdown you'd have written anyway.
API endpoint monitor
Log checks and chart uptime and p50/p95 latency with real in-browser Python. No agent, no backend.
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Homelab inventory
Hosts, services, IPs and status in one file you can grep, diff and commit. The app is the file.
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Benchmark log
Record runs with config and result; min/max/avg update live and Python plots the trend so regressions pop.
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RFC & reading tracker
The scratch-file reading queue every engineer keeps — but reactive, ratable and shareable with the team.
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The app is text you can read
Source on the left, live app on the right: every keystroke recompiles instantly. What you see is an API endpoint monitor — form, editable table and real in-browser Python computing uptime and p50/p95 latency — in a couple dozen lines of Markdown. No JSX, no config, no toolchain.
The split editor: Markdown becomes forms, tables and statistics as you type.
How it works
1
Write
Standard Markdown plus a handful of directives: ::input, :::list, :sum, :::python. Or describe the app to the local AI assistant and let it write the source.
2
The browser compiles
No server, no build step, no bundler: the file becomes an interactive app as you type, and its data is persisted on your device.
3
Ship it as a file
An app is a file — commit it, diff it, share it with a link. Turn on encrypted sync and whoever opens it edits the same data in real time.
Why Reactive
Six reasons it's unlike the SaaS you'd otherwise reach for.
Apps are plain files
An app is a Markdown document — create it, git commit it, diff it in a pull request, grep it, back it up. No database, no proprietary format, no vendor to outlive your data.
Real Python in the browser
Actual CPython on WebAssembly, with numpy, pandas and matplotlib. Your code reads the app’s data and renders charts that recompute on their own — no kernel to run, no notebook server to babysit.
Encrypted sync you can self-host
A secret in the file turns on multi-user sync: edits merge without conflicts (CRDT) and a relay only routes end-to-end encrypted blobs — it can’t read them. The relay is a single dependency-free script you can run yourself.
A local AI copilot
An optional chat, running locally with Ollama, helps you build the document: it knows the directives and proposes targeted, reviewable diffs instead of rewriting everything. No cloud, no API key, no data leaving your machine.
No server, no account, no lock-in
Nothing to deploy, no sign-up, no subscription, no build pipeline. It opens and runs from a static file — host it anywhere, or just open the .md.
Privacy by construction
Every app stores its data only in your browser, isolated per app. Nothing is ever transmitted unless you switch on encrypted sync. It’s not a promise — it’s how the thing is built.
Your apps, one library
Every app you open or create lives in your library: launch it, rename it, duplicate it, export it as an .md file — and share it with a link.
The gallery: apps launch with one click and remain yours, in your browser.
A catalog of ready-made apps
Want a starting point instead of a blank file? Browse ready-made apps by category — open one with a click, then fork the source.
Developer tools7
Homelab & self-hosting7
Data & analysis6
DevOps & automation6
Engineering productivity6
Browse all 32 apps →
What you can build
Section titled “What you can build”
Data-entry forms with full CRUD, lists, cards and tables with filtered, sorted and grouped views, reactive statistics, Mermaid diagrams, math formulas and Python analysis with charts — all by writing text.
Start with the step-by-step guide or browse the complete tag reference.
Ready to try?
It opens and runs right in your browser: no install, no sign-up, and the data stays yours.
Open the app