When using defer, scripts are executed in the same order that they are called. This means that the file starts downloading while the HTML document parsers, and even if finished loading, the file waits to be executed until after the HTML is fully parsed.
Using the async attribute to load a resource may look something like this:ĭefer downloads the file asynchronously but is only executed after the HTML document parsing is complete. This means the file starts downloading while the HTML document parsers, and once downloaded, parsing is stopped for the script to execute and then continues parsing. Async and defer attributes can be used to control how and when external files are fetched and executed.Īsync allows for the file to be downloaded asynchronously and then executed as soon as it’s downloaded. If that’s not possible, you may use async or defer attributes to load scripts in the tag. This will allow the page to load first and eliminate any render-blocking from JavaScript. It’s best practice to load all script resources below the fold and above the tag. Using Async and Defer Attributes to Load Script Web Font Loader will then load the actual font after JavaScript runs. To account for this, I’ve added arial and sans-serif as a fallback for Google’s Open Sans font:Īs I mentioned, it’s crucial to have a fallback font to rely on in your CSS styles in the case (and likelihood) the custom font is taking some time to retrieve and load. NOTE: In this instance, it is possible that the rest of the page may render before the Web Font Loader is executed, which can cause a Flash of Unstyled Text (FOUT) or Flash of Invisible Text (FOIT) so it’s important to have fallback fonts in your CSS.įlash of Unstyled Text (FOUT) will occur when the font starts loading and immediately shows the text with the font-family fallback until the web font loads and the fallback font is replaced with the default font called from your CSS styles.įlash of Invisible Text (FOIT) will occur when the font starts downloading and appears as non-existent until the web font loads and replaces that “invisible” text. Simply add in your custom Google fonts into the families array or specify your Typekit id to load the external font package.
#Render blocking css automize code
You’ll need to reference the JavaScript library, and then you’ll be able to add in your fonts using the WebFont object.Ĭheck out the following webfontloader code example: By adding this code outside of the head section, we can mitigate penalized render-blocking of custom fonts. If you’re having trouble loading external fonts like Typekit or Google Fonts, using a webfontloader allows for some added control when injecting a with JavaScript. Using Webfontloader to Load Fonts into JavaScriptĪnother common performance ding is in the way a page loads fonts.
Again, preload attributes are great to start fetching resources we know that the browser is going to need soon. We specified the preload value using the rel attribute, loaded the source in the href, used the as attribute to specify what type of resource we’re preloading, and then used the onload event to load the source when it’s ready. I’ve also added a noscript fallback for browsers blocking script:
Now, here’s how you can preload that request. Preload attributes allow you to specify resources that will be used shortly after loading them and ensure they are executed in a designated order, ultimately boosting page speed performance.įirst, here’s an example of the common way to load a CSS resource into the head section of a page: Thankfully, using preload attributes in the HTML head, you can define critical resources that should be fetched, including when and how each resource should be applied. Most resources that are specified within JavaScript and CSS penalize performance due to the initial shallow document parser. Using the Preload Attribute for Critical Resources
#Render blocking css automize how to
I will be showing how to pass a few common audit failures to help increase page performance. I highly recommend using PageSpeed Insights to audit which sources may be problematic for your page’s overall performance.
Based on the reactions I received in my first blog, I thought I’d share how to pass Google’s eliminating render-blocking resources task to boost page speed performance. I’ve talked a bit about using Google’s PageSpeed Insight’s tool before and how to eliminate render-blocking CSS in above-the-fold content. As the largest and most influential search engine, Google has a lot of say in the expectations on how businesses present themselves online.
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