I'm writing a script to scrape some data from this. I'm wondering if this file changes often or is different between distros.
The Linux kernel strives to have stable interfaces for everything that applications use. This includes not only system calls but also files under
/proc and under select parts of
/sys (some parts of
/sys are officially unstable and do change, refer to the documentation for details).
/proc/net/dev is documented so it's a stable interface. You can count on it not changing.
It hasn't changed since at least the 2.4 series, more than 10 years ago.