Performance testing new theme for theme store is getting hit with Shopify redirect on speed scores

Short description of issue

Redirects on Shopify previews of development store

Reproduction steps

Hi, I’m helping a developer prepare their theme for submission to the theme store. I’m running tests according to the protocol in this doc Performance best practices for Shopify themes, but having a few challenges:

A. It’s unclear how you’re running Lighthouse and with which settings. I chatted with Mateusz Krzeszowiak, and we think you run testing using PageSpeed Insights (PSI), not Lighthouse in Dev Tools or using the Lighthouse CI. If it’s not PSI, then we need the test emulation settings for device and network speed.

B. The instructions state to create a preview and test with the URL which contains the _bt query param. This theoretically works, but our performance scores are getting hit with an extra redirect on the Shopify side so all of our speed-related metrics are slower by 0.2-5s depending on the server redirect time on your side which seems to vary quite a bit.

Additional info

Lighthouse doesn’t report TTFB directly, but we can see some of the details in the specifics for these 2 audits (Document request latency and Network dependency tree) - see screenshot 1.

In this waterfall from WebPageTest, we can see that the time impact is even greater - the circled part is all the waste from the redirects (minus the early hint link header) - see screenshot 2

Since there is no way to remove the password on the development store, is there a different way we should be testing this? Or was the redirect a recent change that didn’t impact testing profiles before?

What type of topic is this

Troubleshooting

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I am facing the exact same problem. The redirect penalty on preview links makes it impossible to get an accurate Lighthouse/PSI score. Looking forward to hearing how we should properly test this.

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Looks like the docs have changed. Here’s the updated link to the testing process (no change to the process and issue still exists):

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Hi all!

Thank you for your patience. We released a change that lets site speed testing tools (PageSpeed Insights, GTMetrix, WebPageTest, SpeedCurve) access development store preview themes via the .shopifypreview.com domain without having to provide a password.

The new flow would be to copy a preview domain link from a preview bar and append the ?pb=0 to it to hide the bar for the analysis.

Please test the feature and share any feedback. If all goes well and stable, I’ll update the documentation to reflect the new approach.

Cheers!

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