We labor tirelessly to make sure that this never happens, working with our CDN partner to ensure that kits are delivered in a reliable and timely manner around the world. The page will fail to render as long as the request for the kit fails to return a response. What was once a desirable delay in rendering to hide the FOUT becomes a serious problem when the script takes longer than a few seconds to load. Normally, this works great, but the downside of this approach becomes apparent in the rare event that the Typekit script takes too long to load. Once the script has finished loading and executing, the FOUT can be controlled with font events, as we’ve discussed in a previous post. While the Typekit script is loading, rendering of the page is blocked, so text won’t start to render with fallback fonts. This standard embed code takes advantage of the fact that tags block further rendering of the page to help prevent the FOUT. The second tag is a piece of inline JavaScript that actually kicks off font loading using the kit. The first is an external tag that loads the kit JavaScript from our content delivery network (or CDN). Typekit’s standard embed code is just a simple pair of tags. Modern browsers continue downloading other resources on the page while the script is executing, while older browsers put a hold on that too. Because the browser doesn’t know what executing the script will do, it waits until the script is done loading and executing before moving on. The script that’s executing could use document.write() to alter the page, or trigger a redirect to go to a different page entirely. This is because web browsers use a single-threaded model when executing JavaScript. When a web browser parses and renders a web page, a tag will block the rendering of elements and the execution of scripts further down the page. This will help to frame the differences between the standard embed code and asynchronous patterns. Standard Typekit embed codeīefore discussing asynchronous loading patterns, let’s take a detailed look at what happens when using the standard Typekit embed code. In fact, we use the font events asynchronous pattern described below on the Typekit status blog to ensure that our users can reliably read about our system status, even during a font network outage or degradation. But these approaches ensure that your page won’t wait for the kit in the unlikely event that something goes wrong somewhere between the font network and the user. Asynchronous patterns are longer, more difficult to implement, and require extra work to avoid the FOUT. The asynchronous loading patterns that we’ll discuss in this post provide a useful alternative in situations where you must eliminate any possibility that a problem loading the kit could interfere with loading the rest of the page. These advantages make it the right choice for the vast majority of sites. It’s simple, compact, very easy to implement, and automatically helps to prevent the flash of unstyled text (or FOUT). The standard Typekit embed code has many advantages. Update: We now offer an official asynchronous embed code through the Kit Editor, so you no longer have to create your own.
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