Install on macOS, step by step

This page walks through the whole install on a Mac. It takes about ten minutes, most of it the one-time setup on the first start. Nothing is installed system-wide apart from Python itself, if you do not have it yet. The app lives in one folder.

Before you start

• About 2 GB of free disk space where you put the folder.
• An internet connection for the first start. After that the app runs offline.
• Chrome, Edge or Brave if you want the app in a window of its own. With Safari or Firefox as your only browser, it opens in a tab, and works the same.

Step 1: download and unpack

1. Open the Download page of this site and press the download button. The zip is saved in your Downloads folder.
2. Double-click the zip. macOS unpacks it next to the zip, into a folder named something like MeshOptimiser-main.
3. Move that folder where you want to keep it, for example into Documents.
4. Open the folder. You should see start.command, serve.py and index.html, among others. The folder .venv that appears later is hidden in Finder, because its name starts with a dot. Press CmdShift. to show hidden files if you want to see it.

Step 2: Python

The launcher needs Python 3.10, 3.11 or 3.12, and looks for python3.12, python3.11, python3.10 and then python3, in that order. The Python that comes with some Macs, or a newer one such as 3.13, is skipped if it is not a supported version.

You have a supported Python

Nothing to do.

You have none, and you have Homebrew

Homebrew is a tool for installing software from the Terminal. The launcher says “Homebrew is available - installing Python 3.12” and runs it for you. It takes about a minute. Python 3.12 is installed next to anything you already have.

You have neither

The launcher tells you to install Python 3.12 from https://www.python.org/downloads/. Download the macOS installer, run it, then double-click start.command again. Or install Homebrew first (https://brew.sh), and let the launcher do the rest.

Step 3: the first start

1. Double-click start.command. A Terminal window opens. This is the launcher and the server, so leave it open while you work.
2. If macOS says “Operation not permitted” or that it cannot open the file, right-click start.command, choose Open, and then Open again in the dialog. macOS blocks a double-click on a freshly unzipped script the first time. The launcher also removes the download flag from the folder, so this is only needed once.
3. macOS may ask whether Terminal can access files in the folder where you put the app, for example Documents. Allow it. The app cannot read its own files without it.
4. The launcher prints that it is creating a virtual environment in .venv, with the version of Python it found, and builds the app’s private Python environment (about 30 seconds).
5. Then it prints Installing/updating Python dependencies... and installs the three add-ons the converter needs: cadquery-ocp (the CAD reader), trimesh and numpy. This is the step that needs the internet, and takes one to three minutes. The text scrolls quickly. It is working, even if it looks quiet for a while.
6. Finally it prints Starting server.... The app opens in a window of its own (or in your browser) and shows the start screen.

Every later start skips the setup and takes a second or two.

Step 4: check that it works

1. On the start screen, click one of the four shapes (Cube, Sphere, Cylinder or Torus). It opens in the 3D view. This needs no file, so it is a quick way to know that the app itself is fine.
2. Press F1 to open the help window, and Esc to close it again.
3. Optional: drag a small STEP file onto the window, to test the converter as well. See Open your first file.

If something stopped on the way, find the message in Install problems, message by message.

Start it from the Terminal instead

You can also run the launcher from a terminal opened in the app folder. This is useful when you want to see every message, pass an option or open a file straight away:

A file name opens that file. Anything that starts with two dashes is passed on to the server; --tab opens the app in an ordinary browser tab instead of a window of its own.

What the install left on your computer

• The app folder, with a .venv folder (up to about 2 GB) and an inbox folder (converted files) inside it.
• Python 3.12, only if you or the launcher installed it for this.
• Nothing else. Your settings are kept by your browser.