PageSpeed Insights 99/100 because of Google Analytics - How can I cache GA?

Here is a really simple solution using JS, for basic GA tracking, which will also work for edge caches/proxies (this was converted from a comment):

if(navigator.userAgent.indexOf("Speed Insights") == -1) {
  (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
  (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
  m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
  })(window,document,'script','https://www.google-analytics.com/analytics.js','ga');

  ga('create', 'UA-XXXXXXXXX-X', 'auto');
  ga('send', 'pageview');
}

Note: This is the default GA script. You may have other ga() calls, and if so, you would need to always check the user agent before calling ga(), otherwise it may error out.

There's a subset of Google Analytics js library called ga-lite that you can cache however you want.

The library uses Google Analytics' public REST API to send the user tracking data to Google. You can read more from the blog post about ga-lite.

Disclaimer: I am the author of this library. I struggled with this specific problem and the best result I found was to implement this solution.

Well, if Google is cheating on you, you can cheat Google back:

This is the user-agent for pageSpeed:

“Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.8 (KHTML, like Gecko; Google Page Speed Insights) Chrome/19.0.1084.36 Safari/536.8”

You can insert a conditional to avoid serving the analytics script to PageSpeed:

<?php if (!isset($_SERVER['HTTP_USER_AGENT']) || stripos($_SERVER['HTTP_USER_AGENT'], 'Speed Insights') === false): ?>
// your analytics code here
<?php endif; ?>

Obviously, it won't make any real improvement, but if your only concern is getting a 100/100 score this will do it.