Fix Search-related JavaScript problems

This guide helps you identify and fix JavaScript issues that may be blocking your page, or specific content on JavaScript powered pages, from showing up in Google Search. While Googlebot does run JavaScript, there are some differences and limitations that you need to account for when designing your pages and applications to accommodate how crawlers access and render your content.

Googlebot is designed to be a good citizen of the web. Crawling is its main priority, while making sure it doesn't degrade the experience of users visiting the site. Googlebot and its Web Rendering Service (WRS) component continuously analyze and identify resources that don’t contribute to essential page content and may not fetch such resources. For example, reporting and error requests that don’t contribute to essential page content, and other similar types of requests are unused or unnecessary to extract essential page content.

If you suspect that JavaScript issues might be blocking your page, or specific content on JavaScript powered pages, from showing up in Google Search, follow the steps below:

To test how Google crawls and renders a URL, use the Mobile-Friendly Test or the URL Inspection Tool in Search Console. You can see loaded resources, JavaScript console output and exceptions, rendered DOM, and more information by clicking the more information link on the page verdict card.

Optionally, we also recommend collecting and auditing JavaScript errors encountered by users, including Googlebot, on your site to identify potential issues that may affect how content is rendered.

Show example

Here's an example that shows how to log JavaScript errors that are logged in the global onerror handler.

window.addEventListener('error', function(e) {
    var errorText = [
        e.message,
        'URL: ' + e.filename,
        'Line: ' + e.lineno + ', Column: ' + e.colno,
        'Stack: ' + (e.error && e.error.stack || '(no stack trace)')
    ].join('\n');

    // Example: log errors as visual output into the host page.
    // Note: you probably don’t want to show such errors to users, or
    //       have the errors get indexed by Googlebot; however, it may
    //       be a useful feature while actively debugging the page.
    var DOM_ID = 'rendering-debug-pre';
    if (!document.getElementById(DOM_ID)) {
        var log = document.createElement('pre');
        log.id = DOM_ID;
        log.style.whiteSpace = 'pre-wrap';
        log.textContent = errorText;
        if (!document.body) document.body = document.createElement('body');
        document.body.insertBefore(log, document.body.firstChild);
    } else {
        document.getElementById(DOM_ID).textContent += '\n\n' + errorText;
    }

    // Example: log the error to remote service.
    // Note: you can log errors to a remote service, to understand
    //       and monitor the types of errors encountered by regular users,
    //       Googlebot, and other crawlers.
    var client = new XMLHttpRequest();
    client.open('POST', 'https://example.com/logError');
    client.setRequestHeader('Content-Type', 'text/plain;charset=UTF-8');
    client.send(errorText);

});

Make sure to prevent soft 404 errors. In a single-page application (SPA), this can be especially difficult. To prevent error pages from being indexed, you can use one or both of the following strategies:
- Redirect to a URL where the server responds with a 404 status code.
  Show example
```
fetch(`https://api.kitten.club/cats/${id}`)
 .then(res => res.json())
 .then((cat) => {
   if (!cat.exists) {
     // redirect to page that gives a 404
     window.location.href = '/not-found';
   }
 });
```
- Add or change the robots meta tag to noindex.
  Show example
```
fetch(`https://api.kitten.club/cats/${id}`)
 .then(res => res.json())
 .then((cat) => {
   if (!cat.exists) {
     const metaRobots = document.createElement('meta');
     metaRobots.name = 'robots';
     metaRobots.content = 'noindex';
     document.head.appendChild(metaRobots);
   }
 });
```
Tell me more: When an SPA is using client-side JavaScript to handle errors they often report an HTTP status code 200 instead of the appropriate status code. This can lead to error pages being indexed and possibly shown in search results.
Expect Googlebot to decline user permission requests.
Tell me more: Features that require user permission don't make sense for Googlebot, or for all users. For example, if you make the Camera API required, Googlebot can't provide a camera to you. Instead, you should provide a way for users to access your content without being forced to allow camera access.
Don't use fragment URLs to load different content.
Tell me more: A SPA may use fragment URLs (for example https://example.com/#/products) for loading different views. The AJAX-crawling scheme has been deprecated since 2015, so you can't rely on fragment URLs to work with Googlebot. We recommend using the History API to load different content based on the URL in an SPA.
Don't rely on data persistence to serve content.
Tell me more: WRS loads each URL (refer to Introduction to Indexing for an overview of how Google discovers content), following server and client redirects, same as a regular browser. However, WRS does not retain state across page loads:
- Local Storage and Session Storage data are cleared across page loads.
- HTTP Cookies are cleared across page loads.
Use content fingerprinting to avoid caching issues with Googlebot.
Tell me more: Googlebot caches aggressively in order to reduce network requests and resource usage. WRS may ignore caching headers. This may lead WRS to use outdated JavaScript or CSS resources. Content fingerprinting avoids this problem by making a fingerprint of the content part of the filename, like main.2bb85551.js. The fingerprint depends on the content of the file, so updates generate a different filename every time. Check out the web.dev guide on long-lived caching strategies to learn more.
Ensure that your application uses feature detection for all critical APIs that it needs and provide a fallback behavior or polyfill where applicable.
Tell me more: Some web features may not yet be adopted by all user agents and some may intentionally disable certain features. For example, if you use WebGL to render photo effects in the browser, feature detection shows that Googlebot doesn't support WebGL. To fix this, you could skip the photo effect or decide to use server-side rendering to prerender the photo effects, which makes your content accessible to everyone, including Googlebot.
Make sure your web components render as expected. Use the Mobile-Friendly Test or the URL Inspection Tool to check if the rendered HTML has all content you expect.
Tell me more: WRS flattens the light DOM and shadow DOM. If the web components you use aren't using <slot> mechanism for light DOM content, consult the documentation of the web component for further information or use another web component instead. For more information, see best practices for web components.
After you fix the items in this checklist, test your page with the Mobile-Friendly Test or the URL inspection tool in Search Console again.
If you fixed the issue, a green check mark appears and no errors display. If you still see errors, post in the JavaScript Sites in Search Working Group.