Debugging Complex JavaScript SEO Issues

How Do Search Engines Process JavaScript?

​Search engines like Google process JavaScript content through a series of following stages: 

• Crawling
• Rendering
• Indexing

Understanding these stages is crucial for optimizing websites that rely heavily on JavaScript.​

1. Crawling

Search engines use automated programs known as crawlers or spiders (e.g., Googlebot) to traverse the web and discover new or updated pages. 

Traditionally, crawlers retrieved the HTML content of a page without executing JavaScript. However, modern crawlers have evolved to execute JavaScript, enabling them to access content that is dynamically generated. 

This advancement allows search engines to discover and index pages that rely on client-side rendering. ​

2. Rendering

After retrieving a page's HTML, search engines proceed to render the page, similar to how a browser would. This involves executing JavaScript to construct the Document Object Model (DOM), apply styles, and load content. 

Rendering enables search engines to understand the fully loaded page, including content that JavaScript dynamically inserts. 

It's important to note that rendering JavaScript-heavy pages can be resource-intensive and may introduce delays in the indexing process. ​

3. Indexing

Once rendering is complete, search engines analyze the content to determine its relevance and store it in their index. 

This index is then used to serve search results to users. 

Pages that rely heavily on JavaScript for content delivery may experience delays in indexing, as search engines might defer rendering such pages to manage resources efficiently.

Do JavaScript Issues Hurt SEO? ​

JavaScript problems can mess up your website’s SEO big time. If search engines can’t properly load your content, they might not index it correctly. 

For example, when a site depends too much on JavaScript for displaying content but doesn’t use server-side rendering, search engines may only see a blank page or a few basic elements. 

This can push your rankings down or even keep your site out of search results. A common mistake is using JavaScript to create internal links without proper anchor tags. 

If search engines don’t recognize these links, they won’t crawl your pages, making it harder for your site to show up in searches.

How to Find JavaScript SEO Issues

Spotting websites that run on JavaScript frameworks is pretty easy. But finding specific pages or elements that change dynamically? That’s a whole different story. Unless, of course, you’ve got the right website audit tool to do the heavy lifting for you.

1. Google Search Console

Google Search Console (GSC) is a free tool from Google that helps website owners keep track of how their site appears in search results. 

One of its most useful features is the URL Inspection Tool, which gives detailed info on how Google views and indexes a page. 

Just enter a URL, and you’ll see if it’s indexed, any errors found, and even details about structured data or AMP versions. You can also test pages live to spot and fix issues that might be stopping Google from indexing them correctly. 

Another handy feature is the Page Indexing report, which shows all known pages on your site, which ones are indexed, and why some might not be—like crawl problems or server errors.

2. Sitebulb

Sitebulb is a powerful tool for website audits, helping users dig deep into technical SEO. It uses an evergreen Chromium engine, so it can render JavaScript just like search engines do. 

One of its coolest features is the "Response vs. Render" report, which shows the difference between a site's raw HTML and its fully loaded page—great for spotting SEO issues.

The tool also provides clear data visualizations, smart SEO suggestions based on 300+ factors, and easy connections to Google Analytics and Search Console. Whether you're working solo or in an agency, Sitebulb makes optimizing websites a whole lot easier.

3. Chrome DevTools

Chrome DevTools is a must-have for debugging JavaScript SEO issues right in your browser. 

The Elements panel lets you inspect and tweak the DOM and CSS on the spot, making it easy to spot hidden or messed-up elements. 

Over in the Console tab, you’ll see JavaScript errors and warnings, which help track down rendering problems and blocked resources. The Network panel shows how resources load, helping you find delays or missing JavaScript files.

If your site is running slow, the Performance tab breaks down page load times and script execution, giving you key insights to speed things up.

4. Google PageSpeed Insights

Google PageSpeed Insights is a free tool that checks how fast a web page loads on mobile and desktop. It gives a score from 0 to 100—higher scores mean better performance. Along with the score, it provides useful tips to make your site faster and smoother for users. 

The tool looks at two types of data: lab data, gathered in a controlled setup using Lighthouse, and real-world data from actual users through the Chrome User Experience Report (CrUX). It focuses on important speed metrics like Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS). These help measure loading speed, responsiveness, and visual stability. 

Fixing the issues highlighted by the tool can speed up a website, improve user experience, and even help with search rankings.

Other Helpful Tools for JavaScript SEO

1. Lighthouse

Lighthouse is an open-source, automated tool integrated into Chrome DevTools that evaluates web pages on performance, accessibility, SEO, and more. It provides actionable insights to enhance site quality, ensuring better user experiences and search engine visibility. ​

2. Screaming Frog SEO Spider

Screaming Frog SEO Spider is a website crawler that efficiently analyzes site architecture, identifying issues like broken links, duplicate content, and rendering problems. It supports JavaScript rendering, offering insights into how search engines interpret dynamic content.​

3. View Rendered Source Chrome Extension

This extension displays a web page's raw HTML alongside its rendered DOM, highlighting JavaScript-induced modifications. It's invaluable for developers and SEOs to understand how browsers and search engines perceive and process page content. ​

4. JetOctopus JavaScript SEO Page Analyzer

JetOctopus's tool assesses how JavaScript affects page loading metrics, such as First Paint and First Contentful Paint. It identifies if essential content or internal links are obscured from crawlers due to JavaScript, helping in optimizing site accessibility.​

5. Wappalyzer

Wappalyzer is a browser extension that identifies technologies and frameworks used on websites. By detecting JavaScript libraries and platforms, it helps developers and SEOs understand potential implementation impacts on site performance and SEO.

Most Common JavaScript SEO Issues

Since we have established that JavaScript issues can negatively impact SEO, it is essential to examine the key challenges that often arise.

1. Blocked JavaScript and CSS Files

Search engines need to see your website just like a regular visitor does. If Google can’t properly load your pages, it might misinterpret your content, leading to indexing issues. One common mistake? Blocking important files, like JavaScript and CSS, in your robots.txt file.

Googlebot relies on these files to render pages correctly. If they’re restricted, your site might not display as it should, which can hurt your rankings.

To check if everything’s working right, use Google’s URL Inspection Tool in Search Console. Test different pages, especially ones that use unique templates. Ask yourself: Are blocked resources actually important for the content? If so, make sure they’re accessible to search engines.

Also, review your robots.txt file to see if critical directories are blocked. If they are, remove those restrictions so Google can crawl and index your site properly.

2. Non-Standard Link Implementations

​Non-standard link implementations refer to the use of JavaScript to create or manage links in ways that deviate from traditional HTML anchor (<a>) tags with href attributes. Such practices can hinder search engine crawlers from effectively discovering and indexing content, leading to potential SEO challenges.​

Here is an example of Non-Standard Link Implementation: 

In this example, a <span> element is used with an onclick event to navigate to a new page. While this approach may function correctly for users with JavaScript enabled, it poses significant issues for SEO:​

• Crawlability: Search engine bots may not execute JavaScript events like onclick, rendering such links invisible to crawlers. Consequently, the linked pages might remain undiscovered and unindexed.​
• Accessibility: Users with disabilities relying on assistive technologies may find it challenging to navigate these links, as such tools are optimized to recognize standard anchor tags.

So, what is the recommended standard link implementation? Here is what it go:

Using a regular <a> tag with an href makes a big difference. Search engines can easily find and index your page, helping your site rank better. It also makes things smoother for users who rely on assistive tech, making navigation easier. 

Sticking to standard link setups keeps your site both user-friendly and search-engine-friendly.

3. Reliance on Fragment Identifiers

Fragment identifiers, also called hash fragments or anchors, help users jump to a specific part of a web page without reloading everything. This makes navigation smoother and is super useful for linking to certain sections of a page. 

Developers often use them in single-page applications (SPAs) to change content without needing a full page refresh.

But here’s the catch—Googlebot doesn’t treat URLs with hash symbols as separate pages. If the content isn’t already in the source code, it won’t be indexed. To make sure search engines can find and rank your content properly, stick to static URLs without hash symbols. 

Instead of using a hash, try using a question mark (?) or another method to guide search engines to the right page.

4. JavaScript-Based Redirects

​JavaScript-based redirects are client-side mechanisms that instruct browsers to navigate to a different URL by executing JavaScript code, typically using commands like window.location.href. 

Unlike server-side redirects (such as HTTP 301 or 302), which are processed immediately upon the server's response, JavaScript redirects require the browser to load and execute the page's JavaScript, introducing potential delays in redirection. This reliance on client-side execution can pose challenges for search engine crawlers; while modern crawlers like Google's can process JavaScript, there is no guarantee that all crawlers will execute these scripts consistently. 

Consequently, some crawlers might not recognize or follow JavaScript redirects, leading to indexing issues or reduced visibility in search results. 

Due to these potential pitfalls, Google's documentation advises using JavaScript redirects only when server-side or meta refresh redirects are not feasible, emphasizing that they should be considered a last resort. ​

5. Dependence on User Interactions

When crucial website content depends on user interactions such as clicking, hovering, or scrolling, search engine crawlers may be unable to access it. These crawlers do not engage with interactive elements; instead, they process only the static HTML that loads initially. 

As a result, content requiring user input to appear may remain unseen by search engines, leading to incomplete indexing and reduced visibility in search rankings.

For example, an e-commerce website might place product descriptions within collapsible sections or tabs that expand only when clicked. If these details load dynamically through JavaScript, search engines may fail to detect them. This lack of visibility can weaken a page’s relevance in search results, ultimately impacting its SEO performance.

To fix this, make sure important content is included in the page’s initial HTML. JavaScript should enhance the experience, not hide valuable information from search engines. That way, both users and crawlers can access the content easily.

6. Hidden Content Under Tabs or Accordions

Keeping content in tabs or accordions is a great way to keep a webpage neat and easy to navigate. But when it comes to SEO, there's been a lot of debate. 

In the past, search engines like Google didn’t give much importance to content that wasn’t immediately visible. 

Back in 2014, Google’s John Mueller even said that hidden content might not carry as much weight. Things started changing with mobile-first indexing. By 2016, Google’s Gary Illyes clarified that content hidden for user experience wouldn’t be treated differently. 

Even so, some SEO experts have noticed that making all content fully visible sometimes leads to better rankings. That means visibility could still play a role in SEO performance.

So, if you’re using tabs or “click here to see more” buttons to hide content, it’s better to avoid it. Instead, try using CSS and HTML to keep the content in the code but just hidden from view until someone clicks a tab. This way, search engines are more likely to index everything on your page. 

To check if Google can see your hidden content, grab a small piece of text from one of the tabs and search for it using the site: operator along with your webpage’s URL.

When your content pops up on Google Search, that means it’s indexed. Simple as that! If you can find it there, Google has already added it to its system.

7. Dynamic Rendering Challenges

Dynamic rendering might seem like a smart way to handle JavaScript-heavy sites, but it comes with its own headaches. It basically means you’re serving a fully interactive site to users while giving Googlebot a pre-rendered version.

That means you now have two versions of your site to manage, which takes extra time and effort. 

You also have to make sure both versions show the same content because if Google finds major differences, it could index outdated information or even penalize your site for being misleading. 

As of 2023, Google doesn’t recommend this method anymore, so it’s not a great long-term fix.

So, how do you know if your website is using dynamic rendering? To determine if your website employs dynamic rendering:

• User-Agent Testing: Configure your browser to mimic a search engine crawler's user agent, such as Googlebot. If the content served differs from what regular users see, dynamic rendering might be in use. ​
• Disable JavaScript: Access your site with JavaScript disabled. If essential content remains visible, it suggests that crawlers receive a pre-rendered version, indicating dynamic rendering. ​
• Inspect Network Requests: Utilize browser developer tools to monitor network activity. If you observe that content loads without additional JavaScript requests, it may indicate server-side rendering or dynamic rendering.​
• Review Server Configuration: Examine your server settings or consult with your development team to check for configurations that detect user agents and serve different content accordingly.​
• Use Third-Party Tools: Employ services like BuiltWith to analyze your site's technologies. These tools can identify if dynamic rendering solutions, such as Prerender.io, are implemented. 

8. Soft 404 Errors

A soft 404 error occurs when a webpage displays a "not found" message to users while returning a 200 OK HTTP status code to search engines. This mismatch can cause search engines to index pages that do not contain valuable content, potentially affecting SEO performance. 

For instance, in an AJAX-based website, if a data request fails and the page presents a "No results found" message while still sending a 200 OK response, search engines may mistakenly recognize it as a valid page. 

This misinterpretation can lead to indexing errors and reduced search visibility.

To identify this issue, conduct a website crawl using your preferred software. Focus on pages that return a 200 HTTP status code but provide no real value. A clear indication is when multiple pages have the same duplicate title stating that the page does not exist. If JavaScript is involved, ensure that you perform a JS crawl rather than a standard one.

Google Search Console is another useful tool for detecting these errors. It highlights URLs that incorrectly return a 200 status code instead of a proper 404. These are typically categorized as “Soft 404” in the Page Indexing report.

After identifying such pages, update them to return the correct 404 status code. This ensures search engines handle them appropriately.

9. Large or Unoptimized JavaScript Files

Big, clunky JavaScript files can slow down a website, making pages take longer to load. When a browser opens a webpage, it has to download, process, and run all the JavaScript files linked to it. 

If those files are too large, it takes more time and uses up more data, delaying how quickly content appears. This can annoy visitors, causing them to leave before exploring the site. Slow load times also affect SEO since search engines like Google favor faster pages.

To fix this, JavaScript needs to be optimized. One way is minifying, which removes extra spaces and comments to shrink file sizes. 

Compressing files makes them even lighter, improving speed. Asynchronous loading helps by letting the page load without waiting for every script to finish. On top of that, deferring non-essential scripts allows the main content to appear first, making the site feel faster. 

These simple tweaks can improve user experience and help a site rank better in search results.

10. Infinite Scrolling Without Pagination

Googlebot doesn’t interact with web pages like a human. It can’t click buttons or scroll to load more content. If something only appears after a user scrolls or clicks, chances are, Google won’t index it.

Take infinite scroll pages, for example. If products load only when a user scrolls down, Google won’t trigger that action. However, Google does use a tall viewport—about 10,000 pixels—so if content loads within that range, it might get indexed. Anything below that? Probably not. And even then, there’s no guarantee Google will always use that tall viewport. Some pages may get fully rendered, while others won’t.

If your site relies on lazy-loading, make sure important content—like product links and details—is already in the initial HTML. Images can load later, but key information should be there from the start. This helps Google index your site properly without needing extra actions like clicking or scrolling.

To check what Google sees, use the Inspection Tool in Google Search Console. If your important content isn’t in the rendered HTML, search engines won’t pick it up.

Keep Your Site Optimized—Schedule an SEO Audit Today​

JavaScript SEO can be tricky, making it tough for both developers and marketers to keep websites running smoothly and ranking well. 

Since JavaScript changes how content loads, search engines sometimes struggle to crawl and index pages correctly. Fixing these issues takes time and technical know-how. The best way to stay ahead is by running regular SEO audits. 

Tools like those from Jaggery Consulting can help you spot problems early and keep your site in top shape. Staying on top of SEO updates and fixing issues as they come up will help your website stay visible and perform its best.

FAQs

​How does client-side rendering impact search engine indexing of JavaScript-heavy websites?​

JavaScript-heavy websites can be tricky for search engines. Since client-side rendering depends on browsers to load JavaScript, search engines might not see the content right away. That delay can slow down indexing.

​What challenges do infinite scrolling implementations present for SEO, and how can they be mitigated?​

Infinite scrolling is another headache for SEO. Search engines don’t always trigger the JavaScript needed to load more content, making it invisible to crawlers. The fix? Combine infinite scrolling with paginated links so all content gets indexed.

​Why might search engines struggle with indexing JavaScript-generated internal links?​

Internal links made with JavaScript can be a problem too. If they aren’t actual HTML anchor tags, search engines might miss them completely. Sticking to standard links makes navigation smoother for crawlers.

​How can the use of JavaScript frameworks affect SEO performance?​

JavaScript frameworks like React and Angular also bring SEO challenges. Since they rely on client-side rendering, search engines may struggle to process the content. Server-side rendering or pre-rendering can help make pages more search-friendly.

​What role does the 'robots.txt' file play in JavaScript SEO, and how can misconfigurations affect site indexing?​

The ‘robots.txt’ file controls what search engines can access. If it blocks JavaScript or CSS, pages might not load properly, hurting SEO. Making sure essential resources are crawlable keeps everything running smoothly.