How to download Chromium source code?

As of today, you can get it from GitHub:

The official GitHub mirror of the Chromium source: https://github.com/chromium/chromium

Per https://chromium.googlesource.com/chromium/src

git clone https://chromium.googlesource.com/chromium/src

Easy peasy lemon squeezy

Cloning with git clone is a tad slow. See bolded text below.

https://chromium.googlesource.com/chromium/src/+/lkcr/docs/linux_build_instructions.md#get-the-code

Create a chromium directory for the checkout and change to it (you can call this whatever you like and put it wherever you like, as long as the full path has no spaces):

$ mkdir ~/chromium && cd ~/chromium

Run the fetch tool from depot_tools to check out the code and its dependencies.

$ fetch --nohooks chromium

If you don't want the full repo history, you can save a lot of time by adding the --no-history flag to fetch.

Expect the command to take 30 minutes on even a fast connection, and many hours on slower ones.