> ## Documentation Index > Fetch the complete documentation index at: https://docs.squid-id.com/llms.txt > Use this file to discover all available pages before exploring further. # React, Next.js, or custom > Add the Squid ID snippet to a React, Next.js, or custom-built app using the Script component or a layout head so it loads once on every route. For a code-built app, add the script to the document head so it loads once and covers client-side navigation. Copy your snippet from [Install the snippet](/getting-started/install-snippet), then: In Next.js, add the snippet to the head in `app/layout` (App Router) or `pages/_document` (Pages Router). In a plain React app, add it to the `` of `index.html`. Because it lives in the shared document head, it loads once and stays active across client-side navigation. Deploy, then [verify](/getting-started/verify).