"Time to Interact" metric in web performance measurements

Question

Apparently "Time to Interact" is the new metric to use when measuring the perceived speed of a webpage. I'm interested in understanding a bit more about what this actually is.

The term was apparently coined by Radware, and is being pushed as the most meaningful performance measurement (compared to things such as Time to First/Last Byte, Time to Render etc.).

It is described as:

the point which a page displays its primary interactive (think clickable) content, rather than full page load.

This seems pretty subjective to me; what is the "primary interactive content" of a webpage for example?

There have been reports citing results for the measurement, so some how this is being measured, and further, it must be automated as the result sets are pretty big (~500 sites were tested).

Other than the above quote, I cannot find any more information on how to measure this.

As Google are placing more emphasis on above the fold content (or visible content), I am wondering whether this metric is actually more like "Time to First Meaningful Render", i.e. it is contextual to the current page goal. So for example, on an eCommerce site's product page, this could be the main image, and an add to basket link.

I am keen to understand this metric, as to me it does seem like the most useful one. My question is therefore whether anyone is measuring this, and if so how are they doing so?

Answer 1

You kind of answered your own question, it is subjective, and contextual to you current project.

What if I'm testing a site with only HTML without any complex resources? There is no point measuring TTI there. On the other hand, let's see this demo site.

Bigger picture here.

Blue line is marking the "COMContentLoaded" event (main document is loaded and markup parsed), red line indicates the load event, where all page resources are loaded. The TTI line would go in-between the two lines, that is defined differently for each project, based on some essential to interact resources loaded event.

For example, let's say that the pictures on the demo site are not essential to the core features of the site. While the main site loaded in 0.8 seconds, the 3 big pictures took 36 extra seconds to load, so in this case using the overall response time as a KPI would yield ~36second response time, while if you define TTI excluding those big, non essential resources, you end up with < 1s response time.

I am keen to understand this metric, as to me it does seem like the most useful one.

Definitely useful, but as you said it in your question, it's specific to the project. You wouldn't measure TTI on a simple, relatively static web app, you would probably measure overall response time. I always define KPIs "tailored" for the current project, instead of trying to use common metrics, and "force them" on a project.

My question is therefore whether anyone is measuring this, and if so how are they doing so?

Definitely used it before, you should identify the essential resources for your site, and when the last of those resources are loaded, that is your TTI. This could be a javascript file, a css, etc...

Answer 2

Websites are getting more complex. Whereas they might not always contain more content they still have more resources to load as the user interaction/user experience is more complex from a technical point of view. Ajax helps us to load different parts separately. So rather than one page load we have the loading of several small things. And for each of these parts we can measure the loading performance. But there might some parts on the site that might be more important than others. The "primary interactive content" is that part of your view that enables the user to do what he intends to do, for example buy a train ticket. If some advertisement or a special animation on the left side of the screen hasn't loaded this does not prevent the user to buy start buying a ticket. But of course "primary interactive content" as a term is quite vague and you have to define it for your specific application. It is the point an average user can and will start to interact with the website while some parts are sill loading.

This is how I understand the concept and I see the difference to "Time to First Meaningful Render" here: you might have a basket rendered on your eCommerce page but the GUI is not yet responsive. So you see something meaningful but the interactivity is not yet there. Therefore TTI >= TtFMR.

Measuring TTI requires you to define what elements are required for interactivity which not only depends on what the site does but also HOW it does it. So it highly depends on your implementation/technology.