GA4 Support

[paulirish]

I looked into this briefly and figured we should have a tracking issue.. At the very least to point to relevant resources.

As mentioned in the site and readme…

At the moment, the Web Vitals Report only supports Universal Analytics properties. Google Analytics 4 (GA4) is not supported as it's APIs are still in alpha preview and some required features are missing.

I poked at the new Data API, which has a newish 'beta' release (as of July '22). And I'm starting to see hints that it may work here too. (I completely defer to you Phil on what's actually real) :)

I did get https://developers.google.com/analytics/devguides/reporting/data/v1/rest/v1beta/properties/batchRunReports running with a GA4 property of mine. (Though sadly I don't have a wv.js + GA4 combo myself…)

I'm seeing support for Custom Dimensions and metrics.. and it appears to connect with the custom "event"s that are used w/wv.js in GA4?

• https://developers.google.com/analytics/devguides/reporting/data/v1/api-schema#custom_dimensions
• https://developers.google.com/analytics/devguides/reporting/data/v1/api-schema#custom_metrics

If that's true, then perhaps we have all the ingredients we need?

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Separately, in a previous conversion, @philipwalton mentioned there's a Bigtable Export for GA4. https://support.google.com/firebase/answer/7029846?hl=en & https://measuremindsgroup.com/bigquery-with-google-analytics-4 That, at least, could be feasible if a backend is in-scope. ;)

[philipwalton]

I believe it will be possible with the new GA4 APIs, but I think there will be a higher barrier to entry.

The secret sauce that allows this entire tool to work (given GA's lack of support for reporting on percentiles, e.g. p75) is that you can (in most cases) manually calculate percentiles yourself if you have a dimension that is unique per user visit.

The Metric.id property allows you to do that, and in Universal Analytics (UA) we could take advantage of the fact that there were 3 event dimensions (category, action, and label), which allow us to recommend setting this ID as the event label when sending the data to GA (see: UA usage instructions).

With GA4, the only build-in event dimension is the event name, so if we want to use the same strategy with GA4, our only option is to recommend users explicitly set the metric ID via a custom event parameter, which we currently do (see: GA4 usage instructions).

However, the catch with GA4 is that, since this isn't a built-in dimension, we can't query for it out of the box. The site owner has to explicitly create a custom dimension that maps to this event parameter before it's available via API. This isn't difficult to do, but it's yet another step in the setup process that raises the barrier to entry. Also, once you create this custom dimension mapping, the data isn't immediately available so if someone doesn't realize this new step is required, they'll have to wait a few days before this tool will be able to show them any data.

On the plus side, it looks like the limit for high-cardinality dimensions in GA4 is 2 million rows instead of 1 million, which should make it possible for more sites to use this tool than could in the past.

Ultimately I think it's still doable, but I imagine fewer people will use this tool as a result.

[philipwalton]

Another big different between GA4 and UA is the change from segments to audiences. In UA there were a number of useful, built-in segments that made it easy/possible to create default comparisons (e.g. desktop vs. mobile, new vs returning users, converters vs. non-converters, etc.).

In GA4 there is no such thing as segments, now there are audiences, which are entirely user-defined and thus present the same challenges as custom event properties. We could probably "recreate" most of the default segment comparisons using filters, but it's unclear whether/how we could support audience comparisons given that there isn't (at least not yet, AFAICT) any API that lets you query the list of audiences the user has created.

[paulirish]

Thanks for dropping all this knowledge.

the site owner has to explicitly create a custom dimension that maps to this event

Maybe the app could help do that for 'em? https://developers.google.com/analytics/devguides/config/admin/v1/rest/v1beta/properties.customDimensions/create

Dunno.. maybe that's overkill

[tullibo]

Hey guys. 6-7 weeks until UA is turned off, do you guys have an insights/updates on GA4 API timeline? Looks like API still won't be available when UA is turned off in July

We've been using a custom version of the tool extensively at our seo agency wpspeedfix.com and its now a critical part of our workflow and can't live without it so thinking of redevving to use a different underlying analytics product

[tunetheweb]

At present we're not working on porting this tool to GA4. You can see an alternative in this post: https://web.dev/vitals-ga4/