Layout Shift GIF Generator
layout-shift-gif.js - Visualise the Core Web Vitals metric Cumulative Layout Shift (CLS) with a simple GIF.
Easily identify problematic layout shifts in the viewport on mobile and desktop. Available as a simple command line tool, or as an online tool.
Try the Layout Shift GIF Tool
Simply enter an URL and hit generate!
Note: This might take a few minutes depending on current usage. If you can't wait why not try the command line tool.
Not only is layout shift annoying and a bad user experience, it's now part of Google's Core Web Vitals which will become a ranking factor for Google Search in 2021.
Lighthouse is a great tool for identifying your Cumulative Layout Shift (CLS) score, but it's not so great for quickly visualising what's actually changing on a page. The Layout Shift GIF Generator allows you to quickly see which elements are moving around in the viewport and return your CLS metric.
The tool is able to check both a desktop and a mobile viewport.
- The desktop viewport is a standard 1920x1080 resolution.
- The mobile viewport is the Nexus 5X profile from Lighthouse.
Both the CPU and the network are throttled simulating a good 3G network.
Command Line Tool
The command line tool can be installed directly from NPM.
npm install -g layout-shift-gif
Once installed the tool can be used as per the following example.
layout-shift-gif --url https://blacklivesmatter.com/ --device mobile --output layout-shift.gif
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Now uses the updated maximum session window metric for CLS.
Updated to Chromium 90
Updated the boundaries to be inline with the Feb 17th changes to CWV.
- Ignore HTTPS errors. Allowing people to use the CLI tool with their own self-signed certificates.
- A cookie file can now be attached (in the Puppeteer JSON format). This is useful if you need to disable a deliberate pop-up such as a GDPR warning.
- The device viewport width and/or height can be overridden if you wish to generate a gif of different device sizes, or entire pages.
- Now available on NPM.
- All the changes.
- If there is a lot of vertical movement on a page it can be difficult to discern which elements have shifted.
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