Introduction to Google’s JavaScript SEO Update
Google has updated its JavaScript SEO documentation with new guidance on handling canonical URLs for JavaScript-rendered sites. This update also adds corresponding guidance to Google’s best practices for consolidating duplicate URLs. The main focus of this update is to address a timing issue specific to JavaScript sites, where canonicalization can happen twice during Google’s processing.
What’s Changed
The updated documentation notes that Google evaluates canonical signals once when it first crawls the raw HTML, and then again after rendering the JavaScript. If the raw HTML contains one canonical URL and the JavaScript sets a different one, Google may receive conflicting signals. Injecting canonical tags via JavaScript is supported but not recommended, as incorrect implementations can cause issues. Multiple canonical tags or changes to an existing canonical tag during rendering can lead to unexpected indexing results.
Best Practices for JavaScript-Rendered Sites
Google recommends two best practices depending on the site’s architecture. The preferred method is setting the canonical URL in the raw HTML response to match the URL the JavaScript will ultimately render. This gives Google consistent signals before and after rendering. If JavaScript must set a different canonical URL, Google recommends leaving the canonical tag out of the initial HTML to avoid conflicting signals between the crawl and render phases. It’s also essential to ensure only one canonical tag exists on any given page after rendering.
Why This Matters for Developers
This guidance addresses a subtle detail that can be easy to miss when managing JavaScript-rendered sites. The gap between when Google crawls the raw HTML and when it renders the JavaScript creates an opportunity for canonical signals to diverge. If you use frameworks like React, Vue, or Angular that handle routing and page structure client-side, it’s worth checking how your canonical tags are implemented. Look at whether your server response includes a canonical tag and whether your JavaScript modifies or duplicates it. In many cases, the fix is to coordinate your server-side and client-side canonical implementations so they send the same signal at both stages of Google’s processing.
Looking Ahead and Taking Action
This documentation update clarifies behavior that may not have been obvious before. It doesn’t change how Google processes canonical tags. If you’re seeing unexpected canonical selection in Search Console’s Page indexing reporting, check for mismatches between your raw HTML and rendered canonical tags. The URL Inspection tool shows both the raw and rendered HTML, which makes it possible to compare canonical implementations across both phases. By following Google’s best practices and ensuring consistent canonical signals, developers can improve their site’s visibility and indexing.
Conclusion
Google’s update to its JavaScript SEO documentation provides valuable guidance for developers working with JavaScript-rendered sites. By understanding how Google processes canonical URLs and following best practices, developers can avoid common pitfalls and ensure their sites are indexed correctly. This update is a reminder of the importance of attention to detail in SEO and the need for developers to stay up-to-date with the latest best practices. By taking the time to review and implement these guidelines, developers can improve their site’s performance and visibility in search results.