How to see design differences after changing CSS?

Question

css

Now I'm doing layout using SASS and Live.js. In a text editor, I change the SCSS file, 'sass --watch' automatically compiles the CSS, and Live.js loads it into the browser. Conveniently.
But sometimes you need to compare the changed design with what it was before the change. For example I am a refractor and I want to get the exact same design. Or see which of the two options is better.
In principle, you can take screenshots of the page, but it's inconvenient to do it every time and I don't know of good screenshot extensions for Chrome.
I would like to first find some easier way to save previous versions of the design.
Secondly, a certain tool that draws "visual diffs" of two design options.
Do such things exist in nature? How do you solve such problems yourself?

Answer 1

I think that for such cases people use different browser tabs: one leaves the original one, and the second is updated after changing the css.

Answer 2

According to the banal, you do it with Live on the local. What has already been approved is uploaded to the hosting (temporary, original, any, or even another folder on localhost, git or directly). Then you experiment further, you will always have the previous version + its backup comes out, and you change the current version