"The Server Timing header provides a discrete and convenient way to communicate backend server performance timings to developer tools in the browser. Adding timing information to your application enables you to monitor back-end and front-end performance all in one place."

"we have set up a transversal performance monitoring system that provides the basis for actions and a direct assessment of their impact. We no longer address web performance optimization as a problem but rather as a continuous improvement initiative and it perfectly fits with our culture of innovation and excellence."

Measuring Web Performance for Wikipedia using synthetic testing tools

Preload Best Practice: Only use preload="auto" if there is a high probability that the video will be watched. In general, the use of preload="metadata" provides a good balance in data usage vs. startup time, but should be monitored for excessive data usage.

"This extensive review shows how little we really know about performance perception and how inadequate the metrics currently used as industry standards probably are"

"If you’re building a web experience and want to stay fast, a performance budget can be critical. For success, embrace performance budgets and learn to live within them. Network & CPU limits on mobile can require asking hard questions like, “what is really important to my users?”"

Altitude NYC 2018: Making Pinterest Fast | Sarah Dapul-Weberman, Michelle Vu, Pinterest

"Accurately measuring layout on the web is hard. There’s no perfect metric to capture style and layout – or indeed, rendering – even though all three can impact the user experience just as much as JavaScript.

However, it’s important to understand how the HTML5 event loop works, and to place performance marks at the appropriate points in the component rendering lifecycle."

"I hope that this post has extended your vision on web performance beyond the well known barrier app vs network, and that this help you to rethink or improve your app architecture."

"In a perfect world, none of our sites would ever block the main thread unnecessarily. We’d all be using web workers to do our non-UI work, and we’d have shouldYield() and a native Scheduling API) built into the browser.

But in our current world, we web developers often have no choice but to run non-UI code on the main thread, which leads to unresponsiveness and jank."

JavaScript is the web’s CO2.

"Improving performance doesn’t mean we should remove all fonts and images. It just means we should be more aware of how the design decisions we make impact user experience. Performance is a balance between content and design."

We have recently completed a milestone where we were able to drop jQuery as a dependency of the frontend code for GitHub.com. This marks the end of a gradual, years-long transition of increasingly decoupling from jQuery until we were able to completely remove the library.

One thing to take away is that web performance optimization is an art not a science. There is no one laid out path to implementing it . So go ahead, start optimizing your sites and have fun while you’re at it (if you can 💁.)

"Web performance is an intricate topic but well worth the effort. Cutting down initial network requests through progressive enhancement and lazy loading is useful to make initial rendering as fast as possible. Showing basic content first, and then loading enhancements like fonts, media, and scripts later, brings the user experience in harmony with aesthetic designs and business goals."

I thought it would be fun to rank the most troublesome technologies in order of tricksiness. I came up with a top four list.