My favorite CSS hack

There is one CSS snippet that I have been copy-pasting for 5 years:

* { background-color: rgba(255,0,0,.2); }
* * { background-color: rgba(0,255,0,.2); }
* * * { background-color: rgba(0,0,255,.2); }
* * * * { background-color: rgba(255,0,255,.2); }
* * * * * { background-color: rgba(0,255,255,.2); }
* * * * * * { background-color: rgba(255,255,0,.2); }
* * * * * * * { background-color: rgba(255,0,0,.2); }
* * * * * * * * { background-color: rgba(0,255,0,.2); }
* * * * * * * * * { background-color: rgba(0,0,255,.2); }

^ This is one of my favourite inventions.

Update 2020 October. I have since adopted a bit more elaborate snippet:

* { outline: 1px solid rgba(255,0,0,.2); :hover { outline: 1px solid rgba(255,0,0,0.6); } }
* * { outline: 1px solid rgba(0,255,0,.2); :hover { outline: 1px solid rgba(0,255,0,0.6); } }
* * * { outline: 1px solid rgba(0,0,255,.2); :hover { outline: 1px solid rgba(0,0,255,0.6); } }
* * * * { outline: 1px solid rgba(255,0,255,.2); :hover { outline: 1px solid rgba(255,0,0,0.6); } }
* * * * * { outline: 1px solid rgba(0,255,255,.2); :hover { outline: 1px solid rgba(0,255,0,0.6); } }
* * * * * * { outline: 1px solid rgba(255,255,0,.2); :hover { outline: 1px solid rgba(0,0,255,0.6); } }
* * * * * * * { outline: 1px solid rgba(255,0,0,.2); :hover { outline: 1px solid rgba(255,0,0,0.6); } }
* * * * * * * * { outline: 1px solid rgba(0,255,0,.2); :hover { outline: 1px solid rgba(0,255,0,0.6); } }
* * * * * * * * * { outline: 1px solid rgba(0,0,255,.2); :hover { outline: 1px solid rgba(0,0,255,0.6); } }

I first shared it on Quora in 2014 (What are the most interesting HTML/JS/DOM/CSS hacks that most web developers don't know about?) and I still get notifications of someone upvoting this answer daily.

But what does this horrible thing do?

It is meant to be used when you are working with layout, e.g.

The problem is that unless the element on the page has a solid background or it is a picture, you do not see how does it fit into the layout, e.g. most of the text nodes, pictures with transparency, etc.

With the above CSS applied you will see something along the lines of:

Different depth of nodes will use different colour allowing you to see the size of each element on the page, their margin and their padding. Now you can easily identify inconsistencies.

Comments

[Cos]

pretty cool!

[Murrough Foley]

A great little tip.

[jstewart8053]

Genuis!

[Vuong]

It's so nice! :)

[Siarhei Bobryk]

Thanks for sharing!

[co0kie]

I do this often and I just add a new style rule directly in devtools as simple as
*{box-shadow: 0 0 0 1px red}

[polemius]

Thank you! This is very useful!

[нιтєѕн кυмαя]

Reminds me of Addy's CSS Layout debugger

$$('*').map((A,B)=>A.style.outline=`1px solid hsl(${B*B},99%,50%`)

gist.github.com/addyosmani/fd3999e...

[Madison Courto]

This is great, I wrote a quick extension
chrome.google.com/webstore/detail/...

[Josh Humble]

VERY interesting and cool. Thanks for this!