Can I add a before-after slider to Squarespace?

Yes. Use Code Injection to add the OneType Transforms script tag site-wide, then add a Code Block set to HTML with two images inside a div with the ot="before-after" attribute. Requires a Core plan or higher.

Which Squarespace plan do I need for a before-after slider?

You need a Core plan ($23/mo) or higher. Basic and Personal plans do not support Code Injection or JavaScript in Code Blocks, which are required to load the slider script.

Why does the slider not show in the Squarespace editor?

Custom code does not render inside the Squarespace editor. You need to preview or publish your page to see the before-after slider working. This is normal behavior for all custom code on Squarespace.

Before-After Slider for Squarespace - Step by Step