How to configure SeaText for server-side rendering with Next.js

SeaText is a client‑side AI snippet that rewrites headlines, offers, and calls‑to‑action after the page loads. When you run a Next.js app with server‑side rendering (SSR) or static site generation (SSG), the snippet must stay out of the server render path. Otherwise the HTML produced on the server will differ from the HTML that the browser later receives, causing hydration mismatches.

Prerequisites

• A Next.js project (either the Pages Router or the App Router) created with npm create next-app or yarn create next-app.
• Your SeaText snippet (the SEATEXTCODEINTEGRATION block) copied from the SeaText dashboard.
• Basic familiarity with React hooks, useEffect, and dynamic imports.

Why SSR matters and what hydration mismatches are

During SSR, Next.js renders React components on the server and sends the resulting HTML to the browser. The browser then “hydrates” that HTML by attaching React’s event listeners and state. If the HTML that the server sent does not match the HTML that the client generates, React logs a warning like “Hydration failed because the initial UI does not match what was rendered on the server.”

SeaText modifies the DOM after the initial paint – it may change text content, add attributes, or insert new elements. If those changes happen during the server render, the server‑generated markup will already contain the modified text, while the client will apply the same modification a second time, producing a mismatch.

Keeping SeaText strictly client‑side avoids the mismatch. The pattern is:

1. Render a placeholder on the server (often an empty div).
2. Load SeaText only after the component mounts in the browser.
3. Tell React to ignore the part of the tree that SeaText will touch by using suppressHydrationWarning.

Step 1: Create a client‑only SeaText provider

Make a new file components/SeaTextProvider.jsx. Mark it as a client component with the "use client" directive. Inside, use useEffect to inject the script tag. The provider also renders a div that has suppressHydrationWarning so React will not compare its children during hydration.

"use client";
import { useEffect } from "react";

export default function SeaTextProvider() {
  useEffect(() => {
    // Create the script element only in the browser
    const script = document.createElement("script");
    script.src = "https://cdn.seatext.ai/seatext.js"; // replace with your URL
    script.async = true; // Asynchronous loading (source S1)
    script.id = "seatext-snippet";
    document.body.appendChild(script);

    // Cleanup on unmount – useful for hot‑module replacement
    return () => {
      const existing = document.getElementById("seatext-snippet");
      if (existing) existing.remove();
    };
  }, []);

  // The wrapper tells React to ignore any DOM changes SeaText makes
  return 
;
}

Trade‑offs: Using useEffect guarantees the script runs after the first paint, which keeps the initial load fast. The downside is that any SEO‑critical text that SeaText would rewrite will not be present in the server HTML. If that text is required for crawlers, you must provide a static fallback.

Troubleshooting: If the script does not appear in the Network tab, verify that the URL is correct and that your CSP allows script-src https://cdn.seatext.ai. Also check the console for Refused to load the script errors.

Step 2: Load the provider with a dynamic import (ssr:false)

Next.js offers next/dynamic to load components lazily. By passing { ssr: false }, the component is never rendered on the server. This is the core guard against hydration mismatches.

import dynamic from "next/dynamic";

// The dynamic import returns a component that only renders on the client
const SeaText = dynamic(() => import("../components/SeaTextProvider"), {
  ssr: false,
});

Place the SeaText component near the top of your component tree so it runs early, but after the html and body tags have been rendered.

Step 3: Append the script safely with useEffect

The provider’s useEffect (shown in Step 1) does three things:

• Creates a script element with async attribute – this matches the asynchronous loading recommendation from SeaText’s documentation (source S1).
• Appends the script to document.body so it runs in the global scope.
• Removes the script on component unmount to avoid duplicate loads during development hot‑reloading.

Why async matters: An async script does not block the main thread, preserving First Contentful Paint (FCP) and Core Web Vitals. SeaText’s own script is under 15 KB, so the network impact is minimal (source S1).

Step 4: Suppress hydration warnings where SeaText rewrites

SeaText may change the text of headings, button labels, or meta tags. Wrap the area that can change in a div with suppressHydrationWarning={true}. This tells React to skip the strict HTML comparison for that subtree.

<div suppressHydrationWarning={true}>
  <h1>Original headline</h1>
  <button>Buy now</button>
</div>

If you forget this attribute, you will see warnings in the console and possibly a full page re‑render, which can cause flicker.

Step 5: Complete App Router example

The App Router (available from Next.js 13) uses layout.js as the top‑level component. Because layout.js runs on the server by default, you cannot call dynamic(..., { ssr:false }) directly inside it. Instead, create a client‑only wrapper that performs the dynamic import, then mount that wrapper inside the layout.

// components/SeaTextProvider.jsx (already shown above)

// components/SeaTextDynamicWrapper.jsx
"use client";
import dynamic from "next/dynamic";

const SeaText = dynamic(() => import("./SeaTextProvider"), { ssr: false });

export default function SeaTextDynamicWrapper() {
  return ;
}

Now edit app/layout.js:

import "./globals.css";
import SeaTextDynamicWrapper from "../components/SeaTextDynamicWrapper";

export const metadata = {
  title: "My Next.js Site",
  description: "Example with SeaText SSR integration",
};

export default function RootLayout({ children }) {
  return (
    
      
        {/* The wrapper loads SeaText only on the client */}
        
        {children}
      
    
  );
}

Why we need the extra wrapper: The dynamic call itself must be executed in a client component; otherwise Next.js will try to evaluate it on the server and throw an error. By placing the dynamic import inside SeaTextDynamicWrapper (which has "use client"), we keep the import client‑only while still being able to reference it from the server‑rendered layout.

Step 6: Pages Router example (with _app.js vs layout.js note)

If you are using the traditional Pages Router, the entry point is pages/_app.js. The same dynamic import works here because _app.js runs on both server and client, but the component itself is rendered only on the client thanks to ssr:false.

import dynamic from "next/dynamic";
import "../styles/globals.css";

const SeaText = dynamic(() => import("../components/SeaTextProvider"), { ssr: false });

function MyApp({ Component, pageProps }) {
  return (
    <>
      {/* SeaText runs before the page content */}
      
      
    
  );
}

export default MyApp;

Note: In the App Router, the top‑level file is layout.js, not _app.js. The difference matters because layout.js is a server component by default, while _app.js is a hybrid that always renders on the client after the initial server pass. That is why the App Router needs the extra SeaTextDynamicWrapper client component.

Step 7: Verify the integration

1. Run npm run dev and open the site in a browser.
2. Open DevTools → Network and confirm a request to seatext.js appears and has a status of 200.
3. Check the Console for any errors such as "Failed to load script" or CSP violations.
4. Inspect a headline that SeaText is expected to rewrite. The text should change after the page paints (usually within 15 ms, as described in SeaText’s performance docs).
5. View the page source (Ctrl+U). The raw HTML should NOT contain the SeaText script tag – it is injected client‑side only.

Limitations and practical considerations

• SEO‑critical copy: If a headline is essential for search indexing, rely on static content or Next.js metadata instead of SeaText rewrites, because crawlers may not execute the client script.
• Local storage usage: SeaText stores a visitor ID in localStorage. Ensure your site is not served inside an iframe with the sandbox attribute that blocks storage (source S1).
• Cross‑origin policies: Add script-src https://cdn.seatext.ai to your Content Security Policy. If your site serves multiple domains, verify that the script is allowed on each origin (source S1).
• Performance trade‑off: Loading SeaText asynchronously means the rewrite happens after the first paint. In most cases this is fine, but if you need the rewritten copy to be visible before the user can interact, you can poll for window.SeaText and delay UI interactions until the script reports readiness.
• Testing environments: In Jest or Cypress, you may need to mock the dynamic import or the global window.SeaText object to avoid false failures.

Frequently asked questions

Do I need to change my Next.js webpack or Babel config?

No. The dynamic import and client component work with the default Next.js configuration.

Can I use SeaText with static generation (next export)?

Yes. The snippet runs only in the browser, so next export produces static HTML that later loads SeaText client‑side.

What if I still see hydration warnings?

Make sure every element that SeaText may modify is wrapped with suppressHydrationWarning={true}. Also verify that the provider component is truly client‑only (the file must start with "use client").

Will SeaText affect Core Web Vitals?

The script loads asynchronously and runs in under 15 ms, so it has negligible impact on Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS). Keep suppressHydrationWarning to avoid layout shifts caused by React re‑rendering.

How do I handle multiple SeaText agents on the same page?

Load the script once; the global window.SeaText object can manage several agents. Configure each agent via the snippet’s JSON payload as described in the SeaText dashboard.

Is there a size limit for the snippet?

SeaText’s script is under 15 KB, which keeps transfer size low and aligns with the asynchronous loading recommendation (source S1).

Further reading

• Next.js Server‑Side Rendering documentation
• SeaText integration guide for SPAs (source S1)
• Next.js App Router overview