What Does Your User Agent Say About You?


A user agent is a computer program representing a person, for example, a browser in a Web context.

Besides a browser, a user agent could be a bot scraping webpages, a download manager, or another app accessing the Web. Along with each request they make to the server, browsers include a self-identifying User-Agent HTTP header called a user agent (UA) string. This string often identifies the browser, its version number, and its host operating system.

Spam bots, download managers, and some browsers often send a fake UA string to announce themselves as a different client. This is known as user agent spoofing.

The user agent string can be accessed with JavaScript on the client side using the navigator.userAgent property.

A typical user agent string looks like this: "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0".


User Agent String

Browser Data

Googlebot User Agent String

Danielle Fletcher
• Tuesday, 05 July, 2022
• 48 min read

“Crawler” is a generic term for any program (such as a robot or spider) that is used to automatically discover and scan websites by following links from one webpage to another. This table lists information about the common Google crawlers you may see in your referrer logs, and how they should be specified in robots.txt, the robots meta tags, and the X-Robots-Tag HTTP directives.

string agent googlebot


Mozilla/5.0 (Linux; Android 4.2.1; en-us; Nexus 5 Build/JOP40D) Apple WebKit/535.19 (HTML, like Gecko; googleweblight) Chrome/38.0.1025.166 Mobile Safari/535.19 ‡ Chrome/ W.×.Y.Z in user agents Where several user -agents are recognized in the robots.txt file, Google will follow the most specific.

Some pages use multiple robots meta tags to specify directives for different crawlers, like this: Google uses a Chrome-based browser to crawl and render webpages so it can add them to its index.

Web servers can use user agent information to change how they serve the page. The useragentstring is also what helps Sees analyze their log files and understand which pages Google is visiting.

This means that not only will Google bot run the current version of Chrome, give or take just a few weeks, but its useragentstring will then update to include the current version numbers for identifying itself. An evergreen Google bot means leaps and bounds for your render budget.

Where JavaScript’s impact on SEO may have had negative consequences for your website previously, now Google bot can navigate more modern JS language as it continues to update alongside Chrome. This means that the updated user agent has opened the door to 1,000+ JavaScript features.


Additionally, you no longer need to use as many polyfills in JavaScript for functionality in older browsers for Google bot. Previously, when Google bot used an outdated version of Google Chrome, it was important to use polyfills.

Our rendering will always match or exceed Google bot ’s, giving you the most accurate picture of your SEO data. Google recommends that you use feature detection and progressive enhancement instead of user agent sniffing, a tactic sometimes used by smaller, non-enterprise websites.

Feature detection identifies Google bot by matching its capabilities to known features that Google bot supports, while progressive enhancement ensures that websites serve their preferred, full-feature experience to browsers that can handle it while serving a more simple webpage to those that can’t. Using feature detection and progressive enhancement are the more scalable options for enterprise websites long-term and make even more sense now that Google bot ’s useragentstring will continue to update.

At Notify, we’re always thinking ahead and doing our best to anticipate Google’s updates. Therefore, Google’s change to the useragentstring will have no impact on Notify’s reporting.

The only factors that Sees should consider in regard to the new string, and the previously announced evergreen Google bot, is a) reevaluating their usage of polyfills, b) implementing feature detection and progressive enhancement (if they don’t already), and c) keeping an eye on the two points above as suggested by Google. Google bot uses a Chrome-based browser to render webpages, as we announced at Google I/O earlier this year.


In December, we'll start periodically updating the above user agent strings to reflect the version of Chrome used in Google bot. In the following user agent strings, W.×.Y.Z will be substituted with the Chrome version we're using.

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.

Some common issues we saw while evaluating this change include: If you're not sure if your site is affected or not, you can try loading your webpage in your browser using the new Googlebotuseragent.

Posted by Zoe Clifford, Software Engineer in the Web Rendering Service team You might already know that Google’s search engine spiders use the Chrome-based browser to crawl and index webpages.

“In December we’ll start periodically updating the above user agent strings to reflect the version of Chrome used in Google bot. This version number will update on a regular basis,” says Google in the official blog post.


Usually, the updated version of Chrome provides better rendering capabilities, especially when it comes to reading JavaScript. It has to be noted that when Google announced the upgrade of Google bot to Chrome 74, it said the new version supports over 1,000 new features.

When a logged-out user first clicks through to Quora (likely from a search result, since Quora's traffic is heavily based on generating traffic from long tail KW's in the form of questions), the users can view the full page that they've clicked to. Upon clicking any link to another page, a log-in prompt will pop up, requiring that the user log in to continue.

This feature is useful for SEO professionals, for example, to identify issues with cloaking which is against Google’s Webmaster Guidelines or auditing websites which has different look depending on the device. User agent is an HTTP request header string identifying browser, application, operating system which connects to the server.

Get our daily newsletter from SEJ's Founder Loren Baker about the latest news in the industry! The bad bots you definitely want to avoid as these consume your CDN bandwidth, take up server resources, and steal your content.

Good bots (also known as web crawlers) on the other hand, should be handled with care as they are a vital part of getting your content to index with search engines such as Google, Bing, and Yahoo. Read more below about some top 10 web crawlers and user agents to ensure you are handling them correctly.


This file can help control the crawl traffic and ensure that it doesn't overwhelm your server. Google bot is obviously one of the most popular web crawlers on the internet today as it is used to index content for Google's search engine.

Patrick Sexton wrote a great article about what a Google bot is and how it pertains to your website indexing. One great thing about Google's web crawler is that they give us a lot of tools and control over the process.

Bingo is a web crawler deployed by Microsoft in 2010 to supply information to their Bing search engine. Access pages from sites across the Web to confirm accuracy and improve Yahoo's personalized content for our users.

DuckDuckGo is the Web crawler for DuckDuckGo, a search engine that has become quite popular lately as it is known for privacy and not tracking you. These include hundreds of vertical sources delivering niche Instant Answers, DuckDuckGo (their crawler) and crowd-sourced sites (Wikipedia).

They also have more traditional links in the search results, which they source from Yahoo!, Yandex and Bing. Baidu spider is the official name of the Chinese Baidu search engine's web crawling spider.


Soon Spider is the web crawler for, a leading Chinese search engine that was launched in 2004. Note: The Soon web spider does not respect the robots' exclusion standard, and is therefore banned from many websites because of excessive crawling.

Exact is a web crawler for Exiled, which is a search engine based out of France. Part of how this works on the Facebook system involves the temporary display of certain images or details related to the web content, such as the title of the webpage or the embed tag of a video.

One of their main crawling bots is Face bot, which is designed to help improve advertising performance. As you probably know they collect information to show rankings for both local and international sites.

You generally don't want to block Google or Bing from indexing your site unless you have a good reason. Key CDN released a new feature back in February 2016 that you can enable in your dashboard called Block Bad Bots.

Other Articles You Might Be Interested In

01: Screen Reader User Agent
02: Change Browser User Agent Javascript
03: Change Le User Agent Firefox Plugins
04: Change Of User Agent For Edge Browser
05: Change Opera User Agent
06: Change User Agent Bing
07: Change User Agent Ie11
08: Change User Agent Internet Explorer
09: Change User Agent Internet Explorer 10
10: Change User Agent In Brave
1 -
2 -
3 -
4 -
5 -
6 -
7 -
8 -
9 -
10 -