[🐞] High Total Blocking Time (TBT) using Google Analytics and partytown

[benmccann]

Describe the bug

I don't know if this is purely unavoidable. However, it surprised me as I thought Partytown was supposed to move all computations off the main thread.

My page speed score is a couple of points better without Partytown + GA. However, Partytown + GA is still several points better than GA alone.

Reproduction

https://partytown.builder.io/google-tag-manager

Steps to reproduce

Setup Google Analytics with Partytown. E.g. I followed https://partytown.builder.io/sveltekit

Then use https://pagespeed.web.dev/ (look under "Avoid long main-thread tasks") or https://webpagetest.org/ to see that Partytown is significantly blocking the main thread.

Browser Info

Chrome

Additional Information

No response

[benmccann]

Looks like Lighthouse has gotten stricter on its scoring. That amount of blocking time is now taking 7 points of the Lighthouse score

[gioboa]

Can you try with the new release pls? Thanks

[benmccann]

Thank you for taking a look. Unfortunately no improvement

[gioboa]

Here is my result. This is your website, right?

[benmccann]

Yes, that's my site that I've been testing with. The overall score is somewhat variable with some runs doing better than others. Obviously the site scores well overall, but I can't help but want to get to 100 :grin: Probably the most useful piece to look at rather than the overall score is the "Avoid long main-thread tasks" section and see whether Partytown is listed there as contributing to Total Blocking Time. My expectation was that Partytown shouldn't block, but I have limited insight into the internals, so perhaps there's some reason it's not possible for Partytown to operate in a non-blocking way.

[stefan9541]

have the same issue, in my case overall TBT by partytown-sandbox-sw.htm same as I had with Google Analytics and google-tag-manager scripts together)