How to Fix "Warning: Extra Attributes from the Server" in Your Web App

If you’re a web developer, you might’ve run into this pesky message in your console: “Warning: Extra attributes from the server: data-new-gr-c-s-check-loaded, data-gr-ext-installed, cz-shortcut-listen, data-lt-installed”. It’s not a full-blown error, but it’s annoying—and it hints that something’s off in your app. Maybe you’re using React, Next.js, or another framework, and this warning popped up out of nowhere. Don’t worry—you’re not alone, and it’s fixable!

In this guide, we’ll break down what this warning means, why it shows up, and how to get rid of it step-by-step. We’ll keep it simple, so even if you’re new to coding, you’ll get it. By the end, you’ll have a clean console and a smoother app. Let’s dive in and tackle this in 2025 style!

What Does the Warning Mean?

First, let’s decode the message: “Warning: Extra attributes from the server: data-new-gr-c-s-check-loaded, data-gr-ext-installed, cz-shortcut-listen, data-lt-installed”. Here’s the gist:

“Extra attributes from the server”: Your server sent HTML with attributes (like data- tags) that your client-side code didn’t expect.
The attributes: Those funky names (data-new-gr-c-s-check-loaded, etc.) are clues about where they came from.
“Warning”: It’s not breaking your app—just a heads-up that something’s mismatched.

Think of it like ordering a plain burger but getting one with extra toppings you didn’t ask for. It still works, but it’s not what you planned. In tech terms, this often happens with hydration—when server-rendered HTML meets client-side JavaScript.

Why Does This Warning Happen?

This warning pops up in frameworks like React, Vue, or Next.js when there’s a mismatch between what the server renders and what the client expects. Let’s look at the usual suspects behind those specific attributes:

1. Browser Extensions Messing with Your HTML

Those data- attributes scream “browser extension.” Here’s what they likely mean:

data-new-gr-c-s-check-loaded, data-gr-ext-installed: From Grammarly, a popular writing tool. It injects these to track its script loading.
cz-shortcut-listen: Linked to Click-to-Zapier or similar automation extensions, adding shortcuts.
data-lt-installed: LanguageTool, a grammar and spelling checker, marking its presence.

When you (or your users) have these extensions installed, they sneak extra attributes into your HTML after the server sends it but before your app hydrates. Your framework notices the difference and cries foul.

2. Server-Side Rendering (SSR) or Static Site Generation (SSG)

If you’re using SSR or SSG (common in Next.js), the server pre-renders your HTML. But if a client-side extension tweaks that HTML before hydration, React or Vue sees “extra” attributes it didn’t render, triggering the warning.

3. Third-Party Scripts Gone Wild

Maybe you’ve added a script—like an analytics tool or chatbot—that injects attributes into your DOM. If it runs on the client before your app takes over, you’ll see this warning.

4. Testing Environments

Running your app locally with extensions active? That’s a hotbed for this issue. Production might be fine, but your dev setup flags it.

In 2025, with tools like Next.js 14 and React 19 pushing SSR harder, this clash is more common than ever.

Why Should You Care?

It’s just a warning, so why bother? Here’s why it’s worth fixing:

Clean Code: A tidy console builds confidence—no clutter, no doubts.
User Experience: Extensions causing mismatches might slow hydration or confuse your app.
Debugging: Warnings can hide real errors—clearing them keeps your logs sharp.
SEO: Clean HTML matters for crawlers; extra junk might trip them up.

Let’s get that console sparkling clean!

How to Fix the Warning: Step-by-Step Solutions

Here’s a practical roadmap to squash this warning. Start simple, then dig deeper if needed.

Solution 1: Disable Browser Extensions (Quick Test)

Since extensions like Grammarly are prime suspects, let’s rule them out:

Open your app in an incognito/private browser window (Ctrl+Shift+N).
Extensions usually don’t run here—check if the warning vanishes.
If it’s gone, the culprit’s an extension!

Fix:

Disable Grammarly, LanguageTool, etc., in your dev browser.
Ask users to whitelist your site if it’s a production issue (tougher, but possible).

Solution 2: Suppress the Warning (Fast Hack)

If you can’t control extensions (e.g., it’s your users’ browsers), suppress the warning in React or Next.js:

For React

Wrap your app with suppressHydrationWarning:

<div suppressHydrationWarning>
  <YourApp />
</div>

Or, if it’s one element (like <body>):

<body suppressHydrationWarning>
  {children}
</body>

For Next.js

In app/layout.js, add it to the root:

export default function RootLayout({ children }) {
  return (
    <html lang="en" suppressHydrationWarning>
      <body>{children}</body>
    </html>
  );
}

Warning: This hides the symptom, not the cause—use it as a last resort.

Solution 3: Clean Up Client-Side Scripts

Third-party scripts might be injecting those attributes. Check your codebase:

Look in <head> or <body> for <script> tags.
Common culprits: Grammarly widgets, analytics (e.g., Google Tag Manager), or chat tools.
Test by removing them temporarily—does the warning stop?

Fix:

Defer scripts until after hydration with async or defer:

<script src="third-party.js" defer></script>

Or load them dynamically in a useEffect (React):

useEffect(() => {
  const script = document.createElement("script");
  script.src = "third-party.js";
  document.body.appendChild(script);
}, []);

This delays the injection until your app’s ready.

Solution 4: Use a Content Security Policy (CSP)

A CSP locks down what scripts can run, blocking extension meddling:

Add a <meta> tag in your HTML:

<meta
  http-equiv="Content-Security-Policy"
  content="script-src 'self' 'unsafe-inline';"
/>

Or set it in your server config (e.g., Next.js next.config.js):

module.exports = {
  headers: () => [
    {
      source: "/(.*)",
      headers: [
        {
          key: "Content-Security-Policy",
          value: "script-src 'self' 'unsafe-inline';",
        },
      ],
    },
  ],
};

Note: Test carefully—too strict, and legit scripts might break.

Solution 5: Match Server and Client Rendering

If you’re using SSR/SSG, ensure the server and client render the same HTML:

Check Hydration: Extensions might alter HTML post-server but pre-client.
Fix: Pre-render with expected attributes (tricky with extensions) or delay hydration slightly.

For Next.js, try next/script to control timing:

import Script from "next/script";

export default function Page() {
  return (
    <>
      <Script src="third-party.js" strategy="afterInteractive" />
      <div>Your content</div>
    </>
  );
}

Testing Your Fix

After trying a solution:

Clear your console (Ctrl+L or Cmd+K).
Reload your app (F5).
Check for the warning—gone? You’re golden!

Test in production too—local fixes might not catch user-side extensions.

Real-Life Example

Say you’re building a Next.js blog:

Problem: You see the warning with Grammarly active.
Steps:

Test in incognito—warning’s gone.
Add suppressHydrationWarning to <html> in layout.js.
Reload—console’s clean!

Bonus: Switch to defer for Grammarly’s script if you control it.

Fixed in 5 minutes—sweet!

Why This Matters in 2025

With React 19 and Next.js 14 pushing SSR and hydration harder, these warnings are popping up more. Extensions like Grammarly are everywhere, and users won’t disable them. Fixing this keeps your app smooth, your console quiet, and your SEO on point—Google loves clean code!

Final Thoughts

The “Warning: Extra attributes from the server” message—whether it’s data-new-gr-c-s-check-loaded or friends—is a nudge to tidy up. Whether you disable extensions, tweak scripts, or suppress it, you’ve got options. Pick what fits your app and roll with it.

Ever hit this warning? How’d you fix it? Drop a comment—I’d love to hear your story or help with any snags!

How to Fix “Warning: Extra Attributes from the Server” in Your Web App

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