Recently, metrics like Time to Interact (TTI) and Time to First Meaningful Paint (TTFMP) have gotten a lot of attention. Not surprisingly, we sometimes get asked if we'll be adding these metrics to SpeedCurve Synthetic.
We've talked about TTI and TTFMP quite a bit internally. We've decided to hold off on them for a couple of reasons:
- TTI doesn't consistently and accurately measure user experience. Also, because it's based on measurements that are only available in Chrome, it can only give you a partial snapshot.
- While TTFMP – which is available through the new Paint Timing API – measures when content becomes visible in the browser, its weakness is that it gives equal value to every pixel. In other words, it doesn't discriminate between useful and non-useful content.
Having said all that, we're in the process of reviewing TTI for reliability. If it passes scrutiny, we'll definitely consider adding it (with the caveat mentioned above: that it's based on Chrome measurements only).
If not TTI or TTFMP, then what?
If your goal is to understand how users perceive the speed of your site, then SpeedCurve gives you some solid options.
Custom metrics are an extremely reliable measure of user experience, so we strongly encourage our users to explore that option. Custom metrics can be tracked with both Synthetic and LUX Real User Monitoring.
You can also use custom timers to create your own custom Time to Interactive metric, which will be much more meaningful and reliable for your site.
- Steve wrote a great blog post about User Timing and custom metrics.
- He also did a side-by-side evaluation of different rendering metrics.
- Steve and Mark talk about the benefits of custom metrics in this short video:
Hero Rendering Times
We've also created a new set of synthetic metrics – Hero Rendering Times – that are available by default to SpeedCurve users. These metrics measure how quickly critical page assets, such as hero images and H1 elements, render in the browser and they're a solid measure of user experience.
Our RUM tool, LUX, supports custom metrics, as well as measuring Interaction Times based on the behavior of your real users. We feel that Interaction Time is an extremely valuable measure of user experience. The only way to reliably measure this is with RUM, and right now, LUX is the only RUM tool that offers this capability.
You can see how Interaction Times work in the Performance Dashboard our LUX demo:
We're always working to create better UX metrics for performance. We'd love to get your feedback about these metrics and any others on your wishlist.