Get the browser extension

A lighter, browser-integrated version of the converter: it watches your downloads and offers a one-click "Convert to STEP" whenever you download an .stl or .3mf file from any site — no need to open a tab and drag the file in yourself. Everything still runs 100% locally, exactly like the web converter.

Chrome

Version 1.0.0

⬇ Download for Chrome

Microsoft Edge

Version 1.0.0

⬇ Download for Edge

1. Unzip the download

The extension isn't in the Chrome Web Store or the Edge Add-ons store — it's distributed directly as a .zip so anyone can install and inspect it for free. Unzip it anywhere you like (double-click it on Mac, or right-click → "Extract All" on Windows). You'll get a folder — keep it where it is, the browser will keep loading the extension from that folder.

2. Load it into your browser

Chrome:

Open chrome://extensions
Turn on Developer mode (top-right toggle)
Click Load unpacked
Select the unzipped folder

Edge:

Open edge://extensions
Turn on Developer mode (toggle in the left sidebar)
Click Load unpacked
Select the unzipped folder

3. That's it

The converter's icon appears in your toolbar. From then on, downloading an .stl or .3mf from any site (or a .zip from a 3D-model site) pops up a notification with a "Convert to STEP" button. You can also click the toolbar icon any time to open the converter directly and drag a file in by hand.

Browsers show a "Developer mode" warning because unpacked extensions skip the store review process — that's expected here, not a sign of anything wrong. This build is open source: you can read every line before installing it, in the same public repository that powers this website. It asks for no account, sends nothing to any server, and works exactly like the web converter — just with automatic download detection built in.

Why isn't it in the Chrome Web Store or Edge Add-ons yet?

Publishing to the official stores means creating a developer account with Google and Microsoft and going through their review process, which takes time. Rather than make people wait, the extension ships as a direct download in the meantime — the code you'd get from an official listing is exactly the code in this .zip, just without the store's review badge. Store listings are on the roadmap for this project.

What permissions does it ask for, and why?

Chrome's extension permission screen will show two things when you load it, and both map directly to how the extension works:

downloads — needed to notice when you download an .stl or .3mf file, and to read that file's bytes so it can offer to convert it. This is the same API every download-manager-style extension uses.
notifications — used to show the "Convert to STEP" popup after a matching download finishes.
Access to all sites (host_permissions) — this looks broader than it is: Chrome's Manifest V3 downloads API requires a matching host permission before an extension is allowed to read a downloaded file's contents at all, regardless of which site it came from. The extension does not read page content, track browsing, or run on pages you visit — it only ever touches a file after you've chosen to download it.

There's no analytics, no telemetry, and no network request in the extension's code — the actual STL/3MF → STEP conversion runs with the same local, in-browser OpenCascade + WebAssembly engine as the web converter, so a downloaded file never leaves your device.

← Back to the converter