ShowDev: I built a bulk HTML-to-Markdown converter that runs entirely in the browser

#go #ai #webassembly #webdev

Most HTML-to-Markdown tools handle one file at a time. You paste some HTML, get Markdown back, repeat. That works for a quick snippet but not when you have 200+ pages from a help center export sitting in a folder.

I needed exactly that. I had a full site mirror (grabbed with wget --mirror) and wanted clean Markdown I could feed into an LLM knowledge base. Nothing I found could handle it without uploading files to a server or converting one by one.

So I built HTML to Markdown AI.

How it works

You drop a ZIP file (or individual HTML files) into the browser
A Go-based conversion pipeline compiled to WebAssembly processes everything locally
You get a ZIP back with clean GitHub-Flavored Markdown, folder structure preserved

No server involved. Your files never leave your machine.

The conversion pipeline

The heavy lifting happens in Go/WASM. The pipeline:

Strips navigation, footers, scripts, styles, and other boilerplate noise
Extracts the main content from the page
Converts to GFM with proper heading hierarchy, tables, code blocks, and links
Handles batch processing so you can throw hundreds of files at it

Why no built-in crawler?

Intentional decision. Downloading HTML from someone else's site has legal implications depending on jurisdiction and terms of service. I don't want to be in that business.

Downloading is also the easy part:

wget -r -l 0 -np -k -E -p -e robots=off \
  --reject-regex '\.(png|jpe?g|gif|svg|webp|woff2?|ttf|css|js|zip|pdf)$' \
  -w 0.5 --random-wait \
  https://docs.example.com/

That gives you a local folder with all the HTML. The hard and annoying part is turning that into clean, usable Markdown. That's what this tool solves.