Autonomía digital y tecnológica

Código e ideas para una internet distribuida

Linkoteca. Web Performance Optimization

Web font optimization is a critical piece of the overall performance strategy. Each font is an additional resource, and some fonts may block rendering of the text, but just because the page is using WebFonts doesn’t mean that it has to render slower. On the contrary, optimized fonts, combined with a judicious strategy for how they are loaded and applied on the page, can help reduce the total page size and improve page rendering times.

To compress for web at a reasonable broadband bitrate of about 1.5Mbps video / 128kbps audio:

ffmpeg -i source.mp4 -c:v libx264 -b:v 1.5M -c:a aac -b:a 128k target.mp4

To scale down a high-resolution source video to something more reasonable for Web (qHD for cellular, HD for broadband), the -filter:v argument is used:

ffmpeg -i source.mp4 -c:v libvpx-vp9 -b:v 0.33M -c:a libopus -b:a 96k \
-filter:v scale=960x540 target.webm

The loading attribute allows a browser to defer loading offscreen images and iframes until users scroll near them. loading supports three values:

lazy: is a good candidate for lazy loading.
eager: is not a good candidate for lazy loading. Load right away.
auto: browser will determine whether or not to lazily load.

Not specifying the attribute at all will have the same impact as setting loading=auto.

Native lazy loading of images and iframes is super cool. Nothing could be more straightforward than the markup below:

<img src="myimage.jpg" loading="lazy" alt="..." />
<iframe src="content.html" loading="lazy"></iframe>

As you can see, no JavaScript, no dynamic swapping of the src attribute’s value, just plain old HTML.

The loading attribute gives us the option to delay off-screen images and iframes until users scroll to their location on the page. loading can take any of these three values:

lazy: works great for lazy loading
eager: instructs the browser to load the specified content right away
auto: leaves the option to lazy load or not to lazy load up to the browser.