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