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Everything You Need to Know About JavaScript SEO

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If you used JavaScript for your website, be sure you’ve properly taken search engine optimization (SEO) into account. Otherwise, missteps with JavaScript could prevent your site, or at least a part of it, from being indexed on Google and other search engines.

How will your prospects find your website if it’s nowhere in the search results?

That’s why you need to ensure that your use of JavaScript isn’t impeding your SEO.

But first, let’s understand what JavaScript is and how it can impact your search rankings. We will share some useful tips and then explain how to fix common JavaScript SEO mistakes.

What is JavaScript?

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JavaScript is a key component of modern web pages, the others being HTML (HyperText Markup Language) and CSS (Cascading Style Sheets).

There are two ways in which engineers use JavaScript on web pages—embedding it in HTML within <script> tags, or inserting references to it. A gamut of JavaScript libraries and frameworks are currently in use, including jQuery, EmberJS, and AngularJS.

Asynchronous JavaScript combines with XML to enable web applications to have seamless communication with the server, without interfering with the page that appears in the browser.

Async JavaScript code allows other functions to run while it’s functioning. You can have XML deployed for passing data. AJAX is the popular term for this technology. Google Maps is a good example of AJAX in action.

Why JavaScript is Important

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JavaScript is a means of creating powerful applications that are dynamic in the true sense of the word. However, no website can succeed unless it is fully accessible to search engine bots.

Though JavaScript handles bots well, it is important to ensure your script does not obstruct search engine crawlers. This can prevent search engines from properly indexing your pages. If this happens, your pages won’t appear in the search results at all.

Search engine bots process JavaScript web apps in three phases—crawling, rendering, and indexing.

I recommend working with SEO professionals in all these phases to make your JavaScript-backed web applications searchable via Google. 

Understanding the Process

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When a Googlebot visits a web page, it first checks whether you’ve allowed crawling by reading the robots.txt file or the meta robots tag. If this file carries instructions to skip the page, Googlebot will abort the task.

The classic bot approach of making an HTTP request and fetching the URL works efficiently for server-side rendered pages.

However, many JavaScript pages may be using the app shell model, and the initial HTML may not contain the actual content.

In this scenario, the Googlebot would need to execute the JavaScript before it can find the actual page content generated by the script.

The bot would then parse the rendered HTML for links and queue the discovered URLs for crawling. Then the back end processing will use the rendered HTML indexing the page.

Now let’s find out how we can optimize web pages for search engines:

  1. Recheck Robots.txt and Meta Robots Tag

Before launching the website, check your robots.txt file and meta robots tags to make sure someone hasn’t inadvertantly blocked the bots.

Many sites use JavaScript to append a meta robots tag to a page or alter its content. You can change the meta robots tag with JavaScript to facilitate indexing of the web page when an API call returns content.

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Not sure when to use the robots.txt file and meta robots tags? Here is a tip: The .txt file works best for blocking entire sections of websites, while meta tags are used for disallowing individual pages.

All major search engines like Google, Yahoo!, Bing, Baidu, and Yandex support robots meta tag values like index, noindex, follow, nofollow, etc.

You may also issue different instructions to various search engines. For this purpose, you may put in the value of the content attribute to the intended search engine such as Googlebot.

Be careful. Search engine bots will simply ignore instructions that they’re unable to understand.

  1. Use HTTP Status Codes to Interact with Bots

Bots use HTTP status codes to determine what has gone wrong during the crawling process.

Use a meaningful status code to convey to bots if a certain web page should not be crawled or indexed, such as a 401 code for pages requiring a login or 410 for content that has been removed permanently.

HTTP status codes can also inform bots when a page has been moved to a new URL, instructing it to index the new page accordingly.

Here’s a list of meanings of various HTTP codes for your reference:

  • 401/403: Page unavailable due to permission issues
  • 301/302: Page now available at a new URL
  • 404/410: Page unavailable now/forever
  • 5xx: Issues on the server side
  1. Ensure Your Code is Compatible

When writing JavaScript code, you need to ensure it’s compatible with all browsers possible. These browsers use several APIs and your code should be able to hook with most, if not all of these APIs.

Your SEO professionals should be aware of the limitations of these bots regarding various features. At the least, your code should be written to align with the limitations of major search engines like Google and Bing.

Your team needs to be able to identify and resolve JavaScript issues that hinder indexing or display of your page on search engines. In some cases, the code may be blocking specific content on JavaScript-powered pages.

Keep in mind that your perception vs. what the crawlers are actually accessing and rendering may differ unexpectedly. It pays to keep your eyes and your mind open to what may actually be happening.

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To find out how Googlebot is viewing your page, try the URL inspection tool in Google Search Console.

  1. Use Unique Titles and Snippets

Use JavaScript to generate unique titles and snippets, which will help users identify the page. Here is some advice for managing your titles:

  • Every page on your site should have a specific title.
  • Make page titles descriptive and concise.
  • Avoid boilerplate titles such as ‘cheap products for sale’.
  • Avoid any inkling of keyword stuffing.
  • Use titles to provide additional information about your website.

The Google algorithm creates snippets directly from the page content. The search engine may show different content for different searches, depending on the user’s typical search behavior.

There are two techniques to suggest content for these snippets—structured data and meta description tags.

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Structured data [See above image] will help Google understand the page better. It may also use meta tags for presenting a snippet if it decides appropriate content is available there.

  1. Try Lazy-Loading of Images

Images take a toll on your bandwidth and performance. A solution to this issue comes in the form of lazy-loading, which involves loading images later and in a search-friendly manner.

However, be sure lazy-loading does this correctly, or you may inadvertently end up hiding content from the search engine. Use a JavaScript library that supports loading of content when it enters the viewport.

If you favor an infinite scroll experience for your viewers, implement a mechanism to support paginated loading.

It enables your users to share and re-engage with your content. Use the History API to update the URL when your system facilitates dynamic loading of content.

How to Fix Common JavaScript SEO Mistakes

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Now that you’re aware of how to optimize JavaScript-powered web pages for search engines, let’s find out how to fix common JavaScript SEO errors.

Using this guide, you should be able to quickly identify and resolve JavaScript issues that may be preventing rendering of your web pages.

  1. Expecting a Bot to Index Content Requiring User Permission

Googlebot will ignore any content that requires users’ consent. Googlebot and its Web Rendering Service (WRS) clear local storage, HTTP cookies, and session storage data across page loads, so you cannot rely on data persistence to serve content.

Googlebot doesn’t support WebGL. If you’re using WebGL to render photo effects in the browser, deploy server-side rendering to pre-render the photo effects.

  1. Struggling to Ensure Web Components are Search-Friendly

You can resolve this by putting your content into a light DOM (Document Object Model) whenever possible.

Light DOM resides outside the component’s shadow DOM. The markup is written by a user of your component.

Shadow DOM defines the component’s internal structure and scoped CSS. It encapsulates the implementation details.

These techniques eliminate the brittleness of building web apps emanating from the global nature of HTML, CSS, and JavaScript.

For example, when putting a new HTML id/class to use, it may cause a conflict with an existing element on the page.

There may be unexpected bugs, style selectors may go awry, and CSS specificity may become a problem. You can correct these issues by using light and shadow DOMs.

  1. Not Testing Websites for Mobile-Friendly Features

Mobile-friendliness is a key feature of successful websites. Yet many fail to test it before release.

Google offers a tool where you can paste the URL in the provided space, click ‘Analyze,’ and wait a few seconds to find out how mobile-friendly your site is.

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You may also use mobile-friendly test tools offered by independent, third-party service providers. Just be sure it’s mobile-friendly, because Google has already shifted to mobile-first indexing for most domains.


Search engine bots are designed to crawl and index web content in the optimum manner. Unfortunately, they can stumble for a number of reasons, and JavaScript is one of those reasons.

The incorrect or imprecise use of JavaScript could prevent Google crawlers from seeing your web page as a user perceives them, leading to bad organic performance.

Meticulous testing is the best way to ensure that JavaScript on your page is easily accessible to Google.

As the site owner, it is up to you to ensure that your web pages are SEO-friendly. That way, you can derive maximum mileage out of your website investment.

A string of tools are available to assist you in your goal of creating a website that search engines love. That said, your SEO professional’s skills and experience can play a major role as well.

Feature Image Credit: CC 0; Public Domain, sourced from

Disclaimer: The views and opinions stated in this post are that of the author, and Return On Now may or may not agree with any or all of the commentary.

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Vishal Vivek

Founder at SEO Corporation
Vishal Vivek is an eminent Indian serial entrepreneur. Despite having to shoulder huge family responsibilities at a tender age, lack of proper training, and a dearth of resources and funding, he started SEO Corporation and scaled it up to a well-known SEO Company with sheer will power and integrity of character. In the uncertain world of search engine optimization, he is one of the few experts who gives guarantees and honors them. The Times Group recognized him as a legendary entrepreneur and published his biography in the book I Did IT (Vol 2) when he was just 30!

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