JavaScript is an essential programming language for adding dynamic features to websites. However, if not properly optimized for SEO, it can affect crawling and indexing.

In this article, we will discuss the impact of JavaScript on SEO and the key points for optimizing websites using JavaScript.

What is JavaScript SEO?

JavaScript is one of the programming languages ​​​​used to execute actions in a web browser. It controls “actions” like enlarging images for better visibility or setting up input forms to send messages.

While it is as popular as HTML and CSS globally, neglecting SEO can impact crawling and indexing. This concern brings JavaScript SEO into focus.

JavaScript SEO refers to the optimization of websites built with JavaScript to enhance their visibility in search engines.

Since JavaScript can affect essential page elements and ranking factors for SEO, the concept that SEO measures should be applied within JavaScript has gained attention.

Impact of JavaScript on SEO

As mentioned above, JavaScript can significantly influence SEO by affecting page elements and ranking factors.

Its use can lead to bulky code that might stop Google’s crawlers in their tracks or cause difficulties for Googlebot in reading JavaScript, impacting SEO in various ways.

If crawling is halted, the website may not appear in search results. Furthermore, if Googlebot struggles to process JavaScript, it could slow down page loading and image display times, negatively affecting SEO.

The process of Googlebot processing JavaScript

When implementing SEO with JavaScript, understanding how Googlebot processes JavaScript is crucial. Here’s an explanation of the process

Crawling

The process begins with Googlebot, the search engine crawler, navigating through web pages. This process, known as ‘crawling,’ allows Googlebot to understand the content of web pages.

Googlebot first checks if crawling is permitted by reading the robots.txt file and robots meta tags.

Related article: Explaining the Importance of Crawl Budget and 4 Methods to Optimize It!

Rendering

The next step is rendering, which involves processing numerical data to display images, videos, and sounds in the browser.

The crawler analyzes the rendered HTML links and only then moves to the indexing process. The rendering process affects page load time, so if JavaScript loading is slow and Googlebot cannot render correctly, the rendering results need to be checked.

Related article: What is Rendering? Explaining the Relationship between Google Crawler and Rendering

Dynamic Rendering

Handling JavaScript can be complex, and not all search engine crawlers can process JavaScript instantly and correctly. If rendering takes too long, dynamic rendering is recommended.

Dynamic rendering is a method that bypasses rendering for users by creating files with JavaScript for user detection and non-JavaScript HTML files for Googlebot detection.

Sites that frequently post content can implement dynamic rendering to improve the time it takes for their content to appear in search results.

Indexing

Finally, Googlebot performs the indexing of web pages. Indexing refers to registering the page in the search engine’s database. Googlebot analyzes the URL and understands its relevance to the content, then evaluates the page during indexing, which affects its ranking.

These processes are essential for a page to appear in search results, highlighting the importance of having the page crawled and rendered by Googlebot for effective SEO.

Related article: [Advanced SEO Tactics] Controlling Crawling and Indexing

Nine Points for SEO with JavaScript

When using JavaScript, it’s crucial to ensure that Googlebot can correctly crawl and render the content. Here are nine points for SEO with JavaScript

Unique Title and Meta Description

The page title and meta description are often the first elements seen by users. It’s important to make them unique to help users find what they’re looking for easily.

Structured data and meta tags are vital for proposing website snippet content, making it easier for Google to recognize the content of a page.

Be careful not to stuff keywords or make the information too complex and voluminous, as it can detract from user and Google evaluations.

Ensure Code Compatibility. 

When writing JavaScript code, consider browser compatibility. Many APIs are provided by browsers, and your code needs to be compatible with them. Also, be aware of the limitations of search engine crawlers like Google and Bing.

Consider if certain content on your JavaScript-enabled page might be blocked by the code, which could prevent indexing or display of the webpage. Identify and resolve any JavaScript issues that could impede web page indexing or visibility.

Using the appropriate HTTP status codes

Googlebot uses these codes to determine if there are any issues when crawling a page. Websites using JavaScript should also return the correct HTTP status codes.

It’s necessary to understand the meanings of different status codes, such as 301 and 404. HTTP status codes can also communicate to crawlers when a web page has moved to a new URL, facilitating the indexing of the new page.

Recheck robots meta Tags

robots meta tags control how crawlers interact with a page, including whether Googlebot should index it or follow its links. For example, adding a robots meta tag at the top of a page can prevent Googlebot from indexing it.

Therefore, checking the robot.txt file and robots meta tags to ensure they are not accidentally blocking crawlers is crucial.

Test Lazy Loading for Images

Lazy loading for images means loading them as needed, rather than all at once, to improve website performance. However, if not set up correctly, lazy loading can hide content from search engines.

Using JavaScript libraries that support content loading is recommended to prevent this issue. 

Additionally, employing the History API to update URLs can effectively support dynamic content loading.

Instead of using fragments, it’s recommended to utilize the History API

When Googlebot searches for links within a page, it only considers URLs in the href attribute of HTML links. Using fragments to load different content can make it harder for Googlebot to find these links.

The History API facilitates navigation in the browser history, such as going back to a previously viewed page and then returning to the original page. Implementing the History API ensures Googlebot can access link URLs reliably.

Use Long-Term Caching

Googlebot actively stores in cache to reduce network requests and resource usage. However, the Web Rendering Service (WRS) may use outdated JavaScript or CSS resources and ignore cache headers. 

By incorporating a content fingerprint into file names, you can save cache without ignoring cache headers.

Make Web Components Search Engine Friendly

By placing content in the Light DOM, web components become more search engine friendly. Web components are a set of browser APIs that allow encapsulation and reuse of HTML elements within web pages or applications.

While HTML, CSS, and JavaScript are widely used, they have vulnerabilities. Using the Light DOM helps eliminate these vulnerabilities in web application development.

Test for Mobile Friendliness

Mobile friendliness refers to Google’s algorithm, implemented in 2015, that demotes pages not optimized for smartphone viewing. With the increase in smartphone users, the ease of viewing and navigating pages on mobile devices has become crucial.

Making your website mobile-friendly can lead to better evaluations from search engines. Therefore, using Google’s ‘ Mobile-Friendly Test ‘ to thoroughly check the site before launch is important.

Enhancing user experience with Ajax usage

JavaScript is essential for web development, and currently, the technology known as Ajax is gaining attention. Ajax allows asynchronous communication with the server using JavaScript.

It employs a combination of XML, HTML, CSS, and JavaScript to create faster web applications, enabling data transmission to and from the server without disrupting the current page display.

Thus, applying Ajax can enhance the performance and usability of web applications. Although JavaScript usage has been considered problematic for SEO due to potential crawling issues, Ajax has improved the situation. It allows Googlebot to correctly detect and process content loaded from other URLs within a page.

Summary

It was once thought that content powered by JavaScript could be detrimental to SEO. However, with proper SEO strategies, such content can be accurately evaluated by Google. Understanding how Googlebot processes JavaScript and its impact on SEO is crucial. By following the SEO tips discussed, you can effectively utilize JavaScript in your web development.

Author Profile

International Web Consultant Paveena Suphawet

A trilingual professional in English, Thai, and Japanese, she has numerous achievements in international SEO. She studied the latest IT technologies at Assumption International University, Thailand, and majored in International Business at the University of Greenwich, UK. Following her tenure at ExxonMobil’s Thai branch, she became a key member of Admano from its establishment.

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