How do I fix Core Web Vitals on Squarespace?

What to do about it

1. Open Settings, then Advanced, then Code Injection. Every script in the Header field loads on every page of your site. Remove what you no longer need.
2. Upload images close to the size they display. Squarespace builds responsive versions automatically, but a giant original still costs more to process and store than a right-sized one.
3. Use Squarespace’s built-in image and gallery blocks instead of embedded widgets and custom code where you can.
4. Cut back on web fonts: pick one or two families and a few weights. Every font family adds files that delay text and can shift layout.
5. Remove third-party plugins and scripts you bought or pasted years ago. Like Code Injection, they load on every page.
6. Remember the limit: server configuration and caching belong to Squarespace. If server response is the problem, the levers left to you are images, code injection, and fonts.

What WebVitalist checks

The free scan runs 19 technical checks on one public URL. These are the ones that matter for this question:

• HTML size (html-size): The free scan warns when the HTML document is larger than 400 kB, which the browser must download and parse before it can paint anything.
• Server response time (ttfb): Squarespace controls the hosting, so you cannot change the server. The free scan still records server response time, so you know whether delivery or page weight is your problem.

A paid audit ($9 and up) also runs a real mobile Lighthouse test through Google PageSpeed Insights and reads field data for LCP, INP and CLS, where Google has it.