How to ignore whitespace in github when comparing?

git diff -w (alternately git diff --ignore-all-space) ignores whitespace. You can also add --ignore-blank-lines if there are a lot of those.

For more details and many more options, check out the docs.

On github, you simply append the w=1 parameter to the URL for it to ignore whitespace.

That would look something like:

https://github.com/account_name/repo/pull/14/files?w=1

There is a Chrome plugin GitHub Whitespace by jackchuka that appends ?w=1 to the PR URLs so whitespace is always turned off

Since Oct. 2021, this option is now persistent!

Hiding whitespace is now remembered for each pull request

The diff setting to hide whitespace changes in the pull request Files Changed tab is now remembered for you for that pull request.

You no longer need to re-enable it when you switch to another tab or when you come back to the same pull request later.

Learn more about reviewing proposed changes in a pull request.

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Since May 2018, this option is now more visible:

A diff view with reduced white space has been available since 2011 by adding ?w=1 to the URL.
The new button builds on this view to better support your existing workflows.

Select the new option "Hide whitespace changes" in that "Diff settings" new button, and you will see only the relevant changes you want.

Note: since 2018, that setting has been relocated to the setting "gear" symbol: