Show HN: OverType – A Markdown WYSIWYG editor that's just a textarea

The problem I had was simple: I wanted a low-tech way to type styled text, but I didn't want to load a complex 500KB library, especially if I was going to initialize it dozens of times on the same page.

Markdown in a plain <textarea> was the best alternative to a full WYSIWYG, but its main drawback is how ugly it looks without any formatting. I can handle it, but my clients certainly can't.

I went down the ContentEditable rabbit hole for a few years, but always came to realize others had solved it better than I ever could.

I kept coming back to this problem: why can't I have a simple, performant, beautiful markdown editor? The best solution I ever saw was Ghost's split-screen editor: markdown on the left, preview on the right, with synchronized scrolling.

Then, about a year ago, an idea popped into my head: what if we layered a preview pane behind a <textarea>? If we aligned them perfectly, then even though you were only editing plain text, it would look and feel like you were editing rich text!

Of course, there would be downsides: you'd have to use a monospace font, all content would have to have the same font size, and all the markdown markup would have to be displayed in the final preview.

But those were tradeoffs I could live with.

Anyways, version 1 didn't go so well... it turns out it's harder to keep a textarea and a rendered preview in alignment than I thought. Here's what I discovered:

- Lists were hard to align - bullet points threw off character alignment. Solved with HTML entities (• for bullets) that maintain monospace width

- Not all monospace fonts are truly monospace - bold and italic text can have different widths even in "monospace" fonts, breaking the perfect overlay

- Embedding was a nightmare - any inherited CSS from parent pages (margin, padding, line-height) would shift alignment. Even a 1px shift completely broke the illusion

The solution was obsessive normalization:

    // The entire trick: a transparent textarea over a preview div
    layerElements(textarea, preview)
    applyIdenticalSpacing(textarea, preview)

    // Make textarea invisible but keep the cursor
    textarea.style.background = 'transparent'
    textarea.style.color = 'transparent'
    textarea.style.caretColor = 'black'

    // Keep them in sync
    textarea.addEventListener('input', () => {
      preview.innerHTML = parseMarkdown(textarea.value)
      syncScroll(textarea, preview)
    })

That experiment turned into OverType (https://overtype.dev), which I'm showing to you today -- it's a rich markdown editor that's really just a <textarea>. The key insight was that once you solve the alignment challenges, you get everything native textareas provide for free: undo/redo, mobile keyboard, accessibility, and native performance.

So far it works surprisingly well across browsers and mobile. I get performant rich text editing in one small package (45KB total). It's kind of a dumb idea, but it works! I'm planning to use it in all my projects and I'd like to keep it simple and minimal.

I would love it if you would kick the tires and let me know what you think of it. Happy editing!

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Demo & docs: https://overtype.dev

GitHub: https://github.com/panphora/overtype