When we talk about web performance measurement, what we’re actually trying to determine is the moment when a user can effectively achieve his or her goal. Meaning the users can consult the content they are looking for and/or interact with the page  in a satisfactory way. Some metrics endorse rendering actions by the browser, others measure the progress of the display through the recording of a video. However, a great mystery remains: how to properly measure interactivity.

For a few years now, Google has been pushing an ambiguous metric: Time To Interactive. What does it mean? Let’s define it and explain how and when to use it (or not).

Images are a key content on your website? If you’re serious about your website performance, you have probably optimized them. But have you considered to lazy load your images? Lazy loading images improves the user experience by saving bandwidth for important content first.

Some reject the technique for SEO considerations. But properly lazy loading your images does not prevent them from being indexed. Let’s find out why you should implement lazy load, and how to make sure you build it in a SEO friendly way.

Improving the speed at which a web page is displayed often means making the browser’s life as easy as possible. When the browser receives an HTTP response, it actually receives text encoded in bytes, where each byte or sequence of bytes represents a given character. If the browser does not have a clear information about the used encoding, it will waste time trying to guess and may fail in some cases.

Continue reading Content Encoding: why and how to use the meta charset tag and the Content-Type header →

This article is a transcript of my conference about Performance Budgets, held during the We Love Speed event (Bordeaux, October 9, 2018). Continue reading Performance Budgets – We Love Speed 2018 →