How JavaScript Can Break (or Boost) Your SEO

JavaScript is behind some of the most impressive and interactive websites on the internet. But when it comes to SEO, it can either be your best friend—or your worst enemy. In 2025, with Googlebot’s rendering capabilities better than ever, many assume JavaScript no longer poses any SEO issues. Unfortunately, that’s far from the truth.

In this guide, we’ll explain how JavaScript interacts with Google’s crawling and indexing processes, where things can go wrong, and how to ensure your dynamic content is visible and SEO-friendly.

🔍 What Is JavaScript SEO?

JavaScript SEO is the practice of optimising websites that use JavaScript for better visibility in search engines. This includes making sure content rendered with JavaScript is crawlable, indexable, and doesn’t block critical page information from being seen by bots.

🧠 How Googlebot Handles JavaScript

Googlebot now supports JavaScript rendering—but with caveats. It uses a three-phase process:

1. First, it crawls the page and collects the raw HTML.
2. Next, it queues the JavaScript for rendering (this can take time).
3. Finally, once rendered, Googlebot extracts the updated content.

This delay means important JavaScript-rendered content may be missed or delayed in indexing.

⚠️ Common SEO Problems Caused by JavaScript

• 🚫 Hidden Content: If key content loads only after user interaction, Googlebot may never see it.
• 💀 Fragmented Pages: If navigation depends on JavaScript without proper fallbacks, your internal linking structure could be invisible.
• ⏱️ Slow Rendering: Heavy JS scripts delay page rendering, impacting Core Web Vitals and SEO performance.

🔁 SSR vs CSR: Which Is Better for SEO?

Server-Side Rendering (SSR) and Client-Side Rendering (CSR) are two different ways of delivering JavaScript content:

• 🖥️ SSR: Renders the page on the server before sending it to the browser. Best for SEO as search engines get fully-formed HTML.
• 📲 CSR: Loads a blank shell and fills it using JavaScript in the browser. Faster for users but risky for search engines.

If SEO is a priority, SSR or hybrid frameworks like Next.js are generally safer choices.

🧪 JavaScript SEO Tests You Can Run

• 🔎 Use Google Search Console to inspect URLs and compare HTML vs rendered content.
• 🧰 Use SEO tools like Screaming Frog with JavaScript rendering enabled to crawl your site.
• 👁️ Manually view your page with JavaScript disabled—can you still see your content?

🛠️ How to Make JavaScript SEO-Friendly

• 💡 Make core content visible in HTML whenever possible.
• 📜 Use structured data (like FAQ or Article schema) directly in the page’s HTML.
• 🚀 Optimise script loading with lazy loading and defer tags.
• 🌐 Ensure internal links and navigation work without JavaScript.
• 📈 Monitor indexation using tools like Index Coverage in Google Search Console.

📱 Why This Matters in a Mobile-First World

Google’s mobile-first indexing means if your JavaScript content doesn’t work on mobile—or loads too slowly—it may never get indexed at all. Prioritising mobile rendering performance is no longer optional.

✅ Final Thoughts

JavaScript doesn’t have to be a roadblock for SEO—but it can be if you’re not careful. The key is understanding how search engines interact with your content and ensuring they can access, render, and index what matters most. Keep performance high, structure logical, and never assume bots see what users do.

“Modern SEO isn’t just about keywords—it’s about visibility. If search engines can’t see your content, they can’t rank it. JavaScript can help or hinder—make sure it’s working in your favour.”
– David Roche