See Google crawlers (user agents) and Make sure Google can index JavaScript for background reading about user agent strings and rendering.
Googlebot user agents today
Mobile:
Mozilla/5.0 (Linux; Android 6.0.1; Nexus 5X Build/MMB29P) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.96 Mobile Safari/537.36 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
Desktop:
Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
OR
Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; Googlebot/2.1; +http://www.google.com/bot.html) Safari/537.36
The new evergreen Googlebot and its user agent
In December we’ll start periodically updating the above user agent strings to reflect the version of Chrome used in Googlebot. In the following user agent strings, “W.X.Y.Z” will be substituted with the Chrome version we’re using. For example, instead of W.X.Y.Z you’ll see something similar to “76.0.3809.100“. This version number will update on a regular basis.
Mobile:
Mozilla/5.0 (Linux; Android 6.0.1; Nexus 5X Build/MMB29P) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/W.X.Y.Z Mobile Safari/537.36 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
Desktop:
Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
OR
Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; Googlebot/2.1; +http://www.google.com/bot.html) Chrome/W.X.Y.Z Safari/537.36
How to test your site
We’ve run an evaluation, so are confident that most websites will not be affected by the change.
Sites that follow our recommendations to use feature detection and progressive enhancement instead of user agent sniffing should continue to work without any changes.
If your site looks for a specific user agent, it may be affected. You should use feature detection instead of user agent sniffing. If you cannot use feature detection and need to detect Googlebot via the user agent, then look for “Googlebot” within the user agent.
Some common issues we saw while evaluating this change include:
- Pages that present an error message instead of normal page contents. For example, a page may assume Googlebot is a user with an ad-blocker, and accidentally prevent it from accessing page contents.
- Pages that redirect to a roboted or noindex document.
If you’re not sure if your site is affected or not, you can try loading your webpage in your browser using the new Googlebot user agent. These instructions show how to override your user agent in Chrome.
If you have any questions, be sure to reach out to our webmaster help community, join our webmaster office hours on YouTube or follow us on Twitter.