Since DPC handles tracking by observing the DOM it can only run in the browser. This requires DPC to be loaded in a way so that it’s not executed on the server when using a framework capable of Server-side rendering (SSR) like Next.js.

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Initializing DPC in your entry point

In Next.js you can make sure code is only executed client-side by checking typeof window !== "undefined". Since we are importing DPC as a module we can’t do it the with the normal import { DPC } from "depict-ai/dpc" syntax. Instead, we can use dynamic imports. This is also documented by Next.js.
TypeScript
// pages/_app.tsx

import "../styles/globals.css";

/**
 * Initialize Depict Performance Client
 * doc:performance-client
 * Note that this is a client-side only library.
 */
(async function initDepictTracking() {
  if (typeof window !== "undefined") {
    const { DPC } = await import("@depict-ai/dpc");
    new DPC("[MERCHANT_ID]", { market: "se" });
  }
})();

export default function App({ Component, pageProps }) {
  return <Component {...pageProps} />;
}