Checkout Studio is a Shopify app that lets a merchant customise the checkout, thank-you, order-status and customer-account pages from one admin. Build a block in the app, place it in Shopify's checkout editor with a Block ID, and every later edit goes live without touching the editor again.
Under the hood it uses Shopify's own checkout UI extensions and Shopify Functions, so it runs inside checkout at native speed and never injects scripts into your theme. Discount, delivery, payment and validation rules run server-side and work on every Shopify plan. Checkout-page blocks and the branding editor use surfaces Shopify reserves for Shopify Plus stores.