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How to Optimize the Performance (Core Web Vitals) of a Webflow Page

  • #technology
  • #web
  • #performance

Starting last month (June 2021), your page’s Core Web Vitals will be taken into account by Google Search ranking. That means that if you have bad performance results your page might be ranked lower on Google results. You can check how your pages perform on Google Search Console.

If you’re using Webflow, it’s not very clear what are the most effective changes you can bring to improve the performance of your website. That’s why I compiled a list of what I believe are the most impactful improvements for most Webflow websites.

1. Use Image Elements Over Background Images

Image elements have better optimization capabilities than background images. For getting the best results, you will want to replace all background images for image elements. In some cases, you might need to use the object-fit property to reproduce the background behavior.

2. Resize and Compress Images

Image size is often what slows down the load time the most. That’s why it’s important to compress and correctly size them.

There are many tools to resize and compress images, however, none of them were good at optimizing images just by handing an URL of a page. That’s why I built a CLI tool named web-img-optimizer that makes it easy and that works with PNG, JPEG, SVG, and GIF files. You just need to pass the URL of a page you want to optimize and it will download, resize and compress all images that are loaded by an image element.

wio optimize https://webflow.com/

Then you just need to upload the new images into your assets and replace the images with the optimized ones.

3. Preconnect to assets’ origin

Webflow serves uploaded assets such as images and fonts from the domain assets.website-files.com. For loading the assets, the browser needs to make an extra connection to that domain. A preconnect tag informs the browser that your page intends to establish a connection to another origin, and that you'd like the process to start as soon as possible.

Improve the page load speed by adding the following to the top of the head tag in your project’s settings.

<link rel="preconnect" href="https://assets.website-files.com/">

Further reading: Preconnect to required origins

4. Preload LCP Image

Preload allows you to inform the browser about critical resources you want to load as soon as possible. Preload can be a game-changer for improving your page speed.

If the largest visible element within the viewport (LCP) is an image, you can preload it by adding a preload tag to your page such as the one below.

<link rel="preload" as="image" href="https://assets.website-files.com/...hero.png" imagesrcset="https://assets.website-files.com/...hero-p-800.png 800w, https://assets.website-files.com/...hero.png 1400w" imagesizes="(max-width: 479px) 100vw, (max-width: 767px) 100, (max-width: 991px) 600px, 55vw">

web-img-optimizer can automatically identify the LCP image of a page and generate the preload tag that you should add to the top of the head tag in your page’s settings.

wio preload https://webflow.com/

5. Lazy Load Images

Lazy loading is a technique for loading images when they are needed rather than all at once. This can considerably improve your loading speed by deferring the loading of off-screen images.

Webflow lazy load new images by default, but you might still need to update older images. You can set your images to lazy load by updating the “Load” setting on the image settings pane.

You also need to declare the image elements’ width and height, otherwise, lazy loading might not work properly.

The issue is that before the images are loaded, their height on the page is unknown. The browser needs to download the image, observe its aspect ratio, and calculate its height. Before this, all the images have a height of 1px. Since all images have a height of 1px, they are all considered as "within the viewport" and are immediately loaded.

To counter that, you need to indicate the images’ width and height values. web-img-optimizer can list all the width and height values for a page’s image elements with the following command:

wio dimensions https://webflow.com/

You only need then to update your images’ height and width on your image elements’ settings.

It’s also important that you have either height or width set explicitly as Auto in your image’s style settings so that the image resizes without breaking its aspect ratio.

Further Optimizations

If there’s enough demand for the following optimizations, I will post a new blog post covering them. Tweet me @i_gassmann to let me know if you want to see me cover these topics.