Type or paste Markdown on the left and the rendered HTML appears on the right as you type. Tables, task lists, strikethrough, and fenced code blocks all work. Copy the HTML to your clipboard, or download a complete standalone page with styling already inlined. The conversion runs in your browser, so drafts of unpublished writing are never sent anywhere.
Most online text tools send whatever you paste to a server, run the work there, and send a result back. Your words sit in someone else's logs, backups and databases, and you have to trust a privacy policy.
Local-first means the opposite: the whole tool is downloaded to your browser and runs on your own device. Nothing you type is transmitted anywhere: not to us, not to anyone. There is no server that could receive it, which is a stronger guarantee than a promise not to look.
Three consequences worth knowing:
You do not have to take that on trust. Open your browser's developer tools, watch the network panel, and type: nothing appears in it.The network's verify page walks through the same check on every Jamuny tool.
A heading, emphasis and a link
# Release notes Fixed the **login** bug — see [issue 42](https://example.com/42).
<h1>Release notes</h1> <p>Fixed the <strong>login</strong> bug — see <a href="https://example.com/42">issue 42</a>.</p>
CommonMark, plus the GitHub extensions people actually use: tables, task lists, strikethrough, fenced code blocks with language labels, and automatic linking of bare URLs. That covers what you will have written in a README, a pull request description or a documentation site.
What it is not is a renderer for one specific platform's dialect. Reference-style footnotes, definition lists and inline HTML attributes vary between implementations, so if your source depends on a niche extension, check the preview rather than assuming.
Markdown permits raw HTML, and raw HTML permits scripts. Everything rendered here passes through DOMPurify first, which strips script tags, iframes, inline event handlers like onerror, and javascript: URLs from both the preview and the exported file.
That matters more than it sounds. An exported page usually ends up open in someone else's browser: a colleague, a client, a reader. Passing through unsanitised HTML would make this converter a way to hand them something hostile. Safe formatting HTML is preserved untouched; only the executable parts are removed.
The preview itself renders inside a sandboxed iframe with scripts disabled, so even a bypass of the sanitiser has nowhere to run.
Copy produces the body fragment on its own: headings, paragraphs and lists with no doctype or wrapper. That is what you want when pasting into a CMS field or an existing template that already has its own head.
Download produces a standalone document: doctype, character encoding, a title taken from your first heading, and minimal readable styling inlined so it looks intentional when opened directly from a file system. Nothing is fetched from a CDN, so it renders the same offline.
CommonMark plus the GitHub extensions people actually use: tables, task lists, strikethrough, fenced code blocks, and automatic linking of bare URLs.
Safe HTML is preserved. Scripts, iframes, inline event handlers, and javascript: links are stripped from both the preview and the exported file, because an exported page often ends up open in someone else's browser.
Copy gives you the HTML fragment: the body content on its own, ready to paste into an existing page. Download gives you a complete standalone .html document with a doctype, a title, and minimal styling already inlined.