Pagespeed Insights doesn't use gzip

Question

PageSpeed Insights doesn't request files with gzip encodings, which leads to a wrong estimation of files sizes(makes them much bigger then they actually are).

I looked through bunch of similar questions and checked various answers, but nothing helped.

Then I estimated in PSI some of Google applications - google.com itself, youtube and others - and it seems like PSI doesn't recognize gzip on these sites either!

Check this out: https://pagespeed.web.dev/analysis/https-www-youtube-com/1uxys155m3?use_original_url=true&form_factor=mobile

Find a little button "open performance card", it will show a visualization with files that are loaded from an application(youtube.com in this case).

Sizes on the map:

Actual sizes of biggest files in chrome devtools:

You can check it on any site.

So, if I'm correct it's a bug of PSI. Does anybody know a proper way to contact PSI team in this case?

Answer 1

The Treemap shows Resource Size, not Network size.

Network size is important as it correlates to download times.

But the uncompressed Resource size is also important since that impacts memory and processing time after it's downloaded.

For coverage checker in particular, this cannot really be done on a compressed file.

If you select "Big request rows" in Network Panel settings you'll see both the compressed and uncompressed sizes in that.

And there's a separate audit which raises if gzip/br is not used, but in that example it passed - because Lighthouse does know about compression and does use it where possible: