SEO JavaScript Checker

Reliable audits for JavaScript-rendered SEO

SEO JS Checker is a Chrome extension that helps you identify critical JavaScript-related SEO issues. It fetches the page’s raw HTML and compares it to the live, client‑rendered DOM, highlighting differences across head tags, visible text, and links. Use it to quickly spot SEO risks introduced by client‑side rendering.

Quick overview

Manifest V3 Chrome Extension — runs a background service worker, a content script, and a popup UI.
Compares server HTML vs. live DOM to reveal Added/Removed/Changed/Unchanged items.
Audits head tags (title, meta, canonical, robots, preload, preconnect, hreflang, JSON‑LD, Open Graph, Twitter), links, and visible text blocks.
Badge shows change counts or HTTP/unsupported status at a glance.
CSV export from the popup for lightweight reporting.

Why SEO JS Checker?

Modern websites often rely on JavaScript to inject or modify critical HTML tags, from meta descriptions and canonical URLs to structured data and internal links. While convenient for development, this poses real risks for SEO. Search engines may see different content than users if critical tags or text only appear after JavaScript runs, or if server responses differ from the final DOM.

This tool makes those gaps obvious and fast to debug. SEO JS Checker compares the raw HTML delivered by your server against the rendered DOM in your browser, so you can:

Surface SEO‑critical DOM differences without diving into DevTools.
Catch regressions when frameworks or tag managers alter metadata.
Speed up QA across environments and cache states.

Every difference is clearly labelled and grouped, with collapsible sections that make the report easy to scan.

Designed for real-world debugging

SEO JS Checker isn’t just a visual diff tool – it’s built to support practical debugging for dynamic sites:

Re‑fetches the page using the page’s own cookies/credentials (via an injected script) for realistic server HTML.
Groups and filters head/link/text changes so you can focus on what matters.
Works on most http(s) pages; gracefully indicates non‑HTML/unsupported contexts.
Lightweight: vanilla JS, inline CSS in the popup, no bundlers.

Who it’s for

This tool is ideal for:

SEO consultants validating rendering and metadata parity.
Developers shipping SSR/CSR apps who want quick sanity checks.
Technical teams verifying metadata consistency across frameworks like React, Vue, or Next.js
QA and content teams checking links and visible text differences.

Features

Head-tag comparisons: title, meta description, robots, canonical, preload, preconnect, hreflang, JSON‑LD, Open Graph, Twitter Card.
Visible text block diffs for major blocks/headings.
Link grouping: internal vs. external, with Added/Removed/Changed/Unchanged status.
Badge indicators: count of changed head items, HTTP status for non‑200, or an unsupported marker.
Popup tabs: Head, Changes, Links, Text – with filters and CSV export.

How it works

Click the SEO JS Checker icon in your Chrome toolbar.
Review the Head tab to compare raw vs. rendered metadata, headings and structured data.
Switch to Links to filter and inspect internal/external link changes.
Export your findings as JSON, CSV or TXT, or copy a plain-text report.

No setup required – everything runs in your browser, on any valid HTTP or HTTPS page.

Built with clarity and control

SEO JS Checker is intentionally minimal and transparent in its output. There are no external dependencies, no data collection, and no reliance on third-party APIs. Everything happens in-browser, using the page you’re viewing.

Developed by Adam King

This plugin was built by Adam King, a technical SEO consultant with over a two decades of experience helping websites navigate complex SEO issues, including JavaScript and indexing challenges.

Install now

You can get the extension from the Chrome Web Store.

  1. Open Chrome and go to the Chrome Web Store.
  2. Search for SEO JS Checker or visit https://chromewebstore.google.com/detail/seo-js-checker/mllilfpgoolaefgngamnamojfgpggglo.
  3. Click Add to Chrome and confirm.
  4. Navigate to any web page and click the extension icon to run your first audit!

Copyright © 2025 Adam King