JavaScript SEO: 6 Best Practices to Boost Rankings
6 Steps to Get AI to Recommend Your Brand
JavaScript has enabled highly interactive and dynamic websites. But it also presents a challenge: ensuring your site is crawlable, indexable, and fast.
That’s why JavaScript SEO is essential.
When applied correctly, these strategies can significantly boost organic search performance.
For instance, book retailer Follet saw a remarkable recovery after fixing JavaScript issues.
What Is JavaScript SEO?
JavaScript SEO is the process of optimizing JavaScript websites. It ensures search engines can crawl, render, and index them.
Aligning JavaScript websites with SEO best practices can boost organic search rankings. All without hurting the user experience.
Common JavaScript Misconceptions
| Misconception | Reality |
|---|---|
| Google can handle all JavaScript perfectly. | Since JavaScript is rendered in two phases, delays and errors can occur. These issues can stop Google from crawling, rendering, and indexing content, hurting rankings. |
| JavaScript is only for large sites. | JavaScript is versatile and benefits websites of varying sizes. Smaller sites can use JavaScript in interactive forms, content accordions, and navigation dropdowns |
| JavaScript SEO is optional. | JavaScript SEO is key for finding and indexing content, especially on JavaScript-heavy sites. |
Benefits of JavaScript SEO
Optimizing JavaScript for SEO can offer several advantages:
- Improved visibility: Crawled and indexed JavaScript content can boost search rankings
- Enhanced performance: Techniques like code splitting deliver only the important JavaScript code. This speeds up the site and reduces load times.
- Stronger collaboration: JavaScript SEO encourages SEOs, developers, and web teams to work together. This helps improve communication and alignment on your SEO project plan.
- Enhanced user experience: JavaScript boosts UX with smooth transitions and interactivity. It also speeds up and makes navigation between webpages more dynamic.
How Search Engines Render JavaScript
To understand JavaScript’s SEO impact, let’s explore how search engines process JavaScript pages.
Google has outlined that it processes JavaScript websites in three phases:
- Crawling
- Processing
- Indexing
Crawling
When Google finds a URL, it checks the [robots.txt](/content/hub/seo/robots-txt "Robots.txt and SEO: Complete Guide"/index.html) file and meta robots tags. This is to see if any content is blocked from being crawled or rendered.
If a link is discoverable by Google, the URL is added to a queue for simultaneous crawling and rendering.
Rendering
For traditional HTML websites, content is immediately available from the server response.
In JavaScript websites, Google must execute JavaScript to render and index the content. Due to resource demands, rendering is deferred until resources are available with Chromium.
Indexing
Once rendered, Googlebot reads the HTML, adds new links to the crawl list, and indexes the content.
How JavaScript Affects SEO
Despite its growing popularity, the question often arises: Is JavaScript bad for SEO?
Let’s examine aspects that can severely impact SEO if you don’t optimize JavaScript for search.
Rendering Delays
For Single Page Applications (SPAs) — like Gmail or Twitter, where content updates without page refreshes — JavaScript controls the content and user experience.
If Googlebot can’t execute the JavaScript, it may show a blank page.
To test how Google will see your SPA site if it can’t execute JavaScript, use the web crawler Screaming Frog. Configure the render settings to “Text Only” and crawl your site.
Indexing Issues
JavaScript frameworks (like React or Angular, which help build interactive websites) can make it harder for Google to read and index content.
For example, Follet’s online bookstore migrated millions of pages to a JavaScript framework.
Google had trouble processing the JavaScript, causing a sharp decline in organic performance:
Crawl Budget Challenges
Websites have a [crawl budget](/content/hub/seo/crawl-budget "What is Crawl Budget? And Why Does It Matter for SEO?"/index.html). This refers to the number of pages Googlebot can crawl and index within a given timeframe.
Large JavaScript files consume significant crawling resources. They also limit Google’s ability to explore deeper pages on the site.
Core Web Vitals Concerns
JavaScript can affect how quickly the main content of a web page is loaded. This affects Largest Contentful Paint (LCP), a Core Web Vitals score.
For example, check out this performance timeline:
JavaScript Rendering Options
When rendering webpages, you can choose from three options: Server-Side Rendering (SSR), Client-Side Rendering (CSR), or Dynamic Rendering. Let’s break down the key differences between them.
Server-Side Rendering (SSR)
SSR creates the full HTML on the server. It then sends this HTML directly to the client, like a browser or Googlebot.
Client-Side Rendering (CSR)
In CSR, the client—like a user, browser, or Googlebot—receives a blank HTML page. Then, JavaScript runs to generate the fully rendered HTML.
Dynamic Rendering
Dynamic rendering, or prerendering, is a hybrid approach.
Tools like Prerender.io detect Googlebot and other crawlers. They then send a fully rendered webpage from a cache.
Which Rendering Approach is Right for You?
The right rendering approach depends on several factors.
| Rendering Option | Best for | When to Choose | Requirements |
|---|---|---|---|
| Server-Side Rendering (SSR) | SEO-critical sites (e.g., ecommerce, blogs)\nSites relying on organic traffic\nFaster Core Web Vitals (e.g., LCP) | Need timely indexing and visibility\nUsers expect fast, fully-rendered pages upon load | Strong server infrastructure to handle higher load\nExpertise in SSR frameworks (e.g., Next.js, Nuxt.js) |
| Client-Side Rendering (CSR) | Highly dynamic user interfaces (e.g., dashboards, web apps)\nContent not dependent on organic traffic (e.g. behind login) | SEO is not a top priority\nFocus on reducing server load and scaling for large audiences | JavaScript optimization to address performance issues\nEnsuring crawlability with fallback content |
| Dynamic Rendering | JavaScript-heavy sites needing search engine access\nLarge-scale, dynamic content websites | SSR is resource-intensive for the entire site\nNeed to balance bot crawling with user-focused interactivity | Pre-rendering tool like Prerender.io\nBot detection and routing configuration\nRegular audits to avoid cloaking risks |
JavaScript SEO Best Practices
So, your site looks great to users—but what about Google?
If search engines can’t properly crawl or render your JavaScript, your rankings could take a hit.
1. Ensure Crawlability
Avoid blocking JavaScript files in the robots.txt file to ensure Google can crawl them.
2. Choose the Optimal Rendering Method
It’s crucial to choose the right approach based on your site’s needs.
3. Reduce JavaScript Resources
Reduce JavaScript size by removing unused or unnecessary code. Even unused code must be accessed and processed by Google.
4. Defer Scripts Blocking Content
You can defer render-blocking JavaScript to speed up page loading.
5. Manage JavaScript-Generated Content
Managing JavaScript content is key. It must be accessible to search engines and provide a smooth user experience.
6. Create Developer-Friendly Processes
Working closely with developers is key to integrating JavaScript and SEO best practices.
JavaScript SEO Resources + Tools
Educational Resources
Understand JavaScript SEO Basics
Google’s JavaScript basics documentation explains how it processes JavaScript content.
Rendering on the Web
The web.dev article Rendering on the Web is a comprehensive resource.
Diagnostic Tools
Screaming Frog & Sitebulb
Crawlers such as Screaming Frog or Sitebulb help identify issues affecting JavaScript.
Semrush Site Audit
Semrush’s Site Audit is a powerful tool for diagnosing JavaScript SEO issues.
Google Search Console
[Google Search Console’s](/content/google-search-console#:~:text=Get%20The%20Most%20Out%20of%20%E2%80%9CURL%20Inspection%E2%80%9D "Google Search Console: The Definitive Guide"/index.html) Inspection Tool helps analyze your JavaScript pages.
Performance Optimization
You may need to test your JavaScript website’s performance.
WebPageTest
WebPageTest helps analyze website performance, including how JavaScript affects load times and rendering.
GTMetrix
GTmetrix helps measure and optimize website performance, focusing on JavaScript-related delays and efficiency.
Chrome DevTools & Lighthouse
Chrome DevTools and Lighthouse are free Chrome tools. They assess site performance and accessibility.
Specialized Tools
Prerender.io helps JavaScript-heavy websites by serving pre-rendered HTML to bots.
Find Your Next JavaScript SEO Opportunity Today
Most JavaScript SEO problems stay hidden—until your rankings drop.
Is your site at risk?
Don’t wait for traffic losses to find out.
Run an audit, fix rendering issues, and make sure search engines see your content.