Markdown Editor

The Markdown editor writes in plain text on one side and shows the rendered preview, the heading outline and a document summary on the other — all in your browser, with no upload.

What is Markdown Editor?

A Markdown editor is worth having because Markdown is legible before it is rendered. You type plain text with a few marks, and the editor shows what those marks will become while you can still read and diff the source. This markdown editor puts the source on the left and the rendered preview on the right, and adds a heading outline and a document summary below so you can see the shape of the draft as you build it.

The renderer implements CommonMark plus the extensions writers reach for: tables, strikethrough, autolinks and task lists. Raw HTML in the source is escaped rather than executed, so a pasted tag is shown as text — which means the preview needs no separate sanitising pass, because there is nothing unsafe to strip. Links are checked by the renderer's own rules, so a javascript: URL in a link destination is not turned into a live link.

The outline is the part that is easy to underrate. Headings are pulled out as a nested list with anchors, so a long document shows its own table of contents without you maintaining one by hand. The summary counts words, lines, headings, links, code blocks and list items, which is enough to tell at a glance whether a section has grown past its budget. Copy the outline or the source with one click.

Because the source is plain text, Markdown travels well. The same file that renders here can become a README, a documentation page, a note in a code review or the body of a static site, and the marks that give it structure stay readable in any plain editor. That portability is the reason to draft in Markdown at all, and the reason the editor keeps the source, the preview and the outline on one screen: you edit the text rather than a formatted document, and you can see the result without leaving the page. Reading the preview also makes a long draft's inconsistencies obvious — a heading used where emphasis was meant, a list that should have been a table — before a renderer turns them into structure.

Nothing on the page is uploaded and nothing is stored beyond the tab: the draft lives in the text area and in whatever you copy or download. There is no account and no network call, so the editor works the same offline as online. The .md file downloads as plain text and renders anywhere Markdown is understood, from a README to a static site.

What the editor does not do is as clear as what it does. It does not syntax-highlight code blocks, render diagrams or typeset mathematics; those are separate concerns with their own tools. It does not export to Word or PDF, and it does not publish anywhere. It is a writing and preview surface for Markdown, and the page says so rather than implying a full desktop editor's feature set. Because the source is plain text, any other Markdown tool can pick it up unchanged, which is the point of choosing this format in the first place.

How to use Markdown Editor

1. Write or paste Markdown into the source pane; the preview updates as you type.
2. Use headings to build the outline; levels one to three are shown in outline form.
3. Read the summary to check words, lines, headings and links.
4. Copy the source or download the .md file; render it wherever you publish.

When to use Markdown Editor vs related tools

Use the Markdown editor when the draft is Markdown and you want the rendered preview and structure beside the source. When you need to see what changed between two versions of a Markdown file, the Document Diff Viewer compares them line by line, and for a plain word and character tally the Word Count Tool is the lighter option.

For prose that wants no chrome at all, the Distraction-Free Writing Editor drops the preview and the panels so only the text is on screen.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.

Frequently asked questions about Markdown Editor