FIT 14.5.3 & Web Accelerator: Delayed iframes and more
In addition to fixing bugs FIT 14.5.3 introduces new and improved Web Accelerator features.
In many modern projects, iframes are used for social media widgets and user tracking. They usually have no impact on the perceived performance of a web page. But there are also sites that have iframes with heavy-weight media content such as youtube videos. Loading megabytes of videos slows down page loading tremendously, even in iframes.
To ensure that users will only load content they are about to see, we introduce delayed iframes. The delayed loading for iframes works exclusively with visibility based loading: The source of the iframe is going to be loaded when the iframes comes close to or into the browser’s viewport, for example by scrolling the page. Due to the unknown nature of the included content of iframes (small tracking and social media vs large videos), the feature cannot be activated globally. You have to enable it in
config.xml and mark the individual
iframe element with the
Probably even more exciting is an improvement we made for delayed images. If the dimensions of images are already known (i.e. the image is in the FIT cache) FIT will generate an SVG image with the same intrinsic size as the final image (instead of a transparent 1x1px GIF). Hence, the layout of the page will remain unchanged when the final image is loaded and replaces the placeholder. This saves a lot of browser reflows and avoids “jumping pages”. The SVG placeholder also clears the way for more promising improvements to the delayed image placeholders, so stay tuned for further news on the topic in upcoming releases.
The SDK for 14.5.3 is available from Github.
Refer to the full changelog for a more detailed list of changes.