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

User Agent Txt

Elaine Sutton
• Thursday, 29 October, 2020
• 23 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.

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Txt to match a crawler type when writing crawl rules for your site. If you need to verify that the visitor is Google bot, you should use reverse DNS lookup.

Mozilla/5.0 (Linux; Android 8.0; Pixel 2 Build/OPD3.170816.012; DuplexWeb-Google/1.0) Apple WebKit/537.36 (HTML, like Gecko) Chrome/74.0.3729.131 Mobile Safari/537.36 (Retrieves favicons for various services) Mozilla/5.0 (X11; Linux x86_64) Apple WebKit/537.36 (HTML, like Gecko) Chrome/49.0.2623.75 Safari/537.36 Google Favicon Web Light error Does not respect robots.

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 If you are searching your logs or filtering your server for an user agent with this pattern, you probably should use wildcards for the version number rather than specifying an exact version number.

Device Atlas Cloud offer a great way to start detecting mobile device traffic to your site: Txt is one of the simplest files on a website, but it’s also one of the easiest to mess up.

Txt file tells search engines where they can and can’t go on your site. Primarily, it lists all the content you want to lock away from search engines like Google.

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Directives are rules that you want the declared user -agents to follow. Disallow Use this directive to instruct search engines not to access files and pages that fall under a specific path.

For example, if you wanted to block all search engines from accessing your blog and all its posts, your robots. If you fail to define a path after the disallow directive, search engines will ignore it.

For example, if you wanted to prevent search engines from accessing every post on your blog except for one, then your robots. Unless you’re careful, disallow and allow directives can easily conflict with one another.

For Google and Bing, the rule is that the directive with the most characters wins. Other search engines listen to the first matching directive.

If you’re unfamiliar with sitemaps, they generally include the pages that you want search engines to crawl and index. If you’ve already submitted through Search Console, then it’s somewhat redundant for Google.

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So you’re best to include sitemap directives at the beginning or end of your robots. Google supports the sitemap directive, as do Ask, Bing, and Yahoo.

For example, if you wanted Google bot to wait 5 seconds after each crawl action, you’d set the crawl-delay to 5 like so: Google no longer supports this directive, but Bing and Yandex do.

That said, be careful when setting this directive, especially if you have a big site. If you set a crawl-delay of 5 seconds, then you’re limiting bots to crawl a maximum of 17,280 URLs a day.

However, on September 1st, 2019, Google made it clear that this directive is not supported. If you want to exclude a page or file from search engines, use the meta robots tag or robots HTTP header instead.

No follow This is another directive that Never Google officially supported, and was used to instruct search engines not to follow links on pages and files under a specific path. Google announced that this directive is officially unsupported on September 1st, 2019.

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If you want to no follow all links on a page now, you should use the robots meta tag or robots header. Txt file isn’t crucial for a lot of websites, especially small ones.

It gives you more control over where search engines can and can’t go on your website, and that can help with things like: Note that while Google doesn’t typically index web pages that are blocked in robots.

This example blocks search engines from crawling all URLs under the /product/ subfolder that contain a question mark. In other words, any parameterized product category URLs.

For example, if you wanted to prevent search engines accessing all .pdf files on your site, your robots. In this example, search engines can’t access any URLs ending with .pdf.

In other words, you’re less likely to make critical mistakes by keeping things neat and simple. Failure to provide specific instructions when setting directives can result in easily-missed mistakes that can have a catastrophic impact on your SEO.

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For example, let’s assume that you have a multilingual site, and you’re working on a German version that will be available under the /DE/ subdirectory. Because it isn’t quite ready to go, you want to prevent search engines from accessing it.

Txt file below will prevent search engines from accessing that subfolder and everything in it: But it will also prevent search engines from crawling of any pages or files beginning with /DE.

In this instance, the solution is simple: add a trailing slash. Txt only controls crawling behavior on the subdomain where it’s hosted.

If you want to control crawling on a different subdomain, you’ll need a separate robot. These are mainly for inspiration but if one happens to match your requirements, copy-paste it into a text document, save it as “robots.

Search engines can still crawl all pages and files. Txt mistakes can slip through the net fairly easily, so it pays to keep an eye out for issues.

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To do this, regularly check for issues related to robots. This means that at least one of the URLs in your submitted sitemap(s) are blocked by robots.

If they are, investigate which pages are affected, then adjust your robots. It’s easy to make mistakes that affect other pages and files.

If this content is important and should be indexed, remove the crawl block in robots. Txt with the intention of excluding it from Google’s index, remove the crawl block and use a robots meta tag or xrobots-header instead.

Once again, if you’re trying to exclude this content from Google’s search results, robots. Remove the crawl block and instead use a meta robots tag or xrobots-tag HTTP header to prevent indexing.

This may help to improve the visibility of the content in Google search. Here are a few frequently asked questions that didn’t fit naturally elsewhere in our guide.

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Txt is a text file webmasters create to instruct web robots (typically search engine robots) how to crawl pages on their website. Txt file is part of the robots' exclusion protocol (REP), a group of web standards that regulate how robots crawl the web, access and index content, and serve that content up to users.

The REP also includes directives like meta robots, as well as page-, subdirectory-, or site-wide instructions for how search engines should treat links (such as “follow” or “no follow”). Txt files indicate whether certain user agents (web-crawling software) can or cannot crawl parts of a website.

After arriving at a website but before spidering it, the search crawler will look for a robot. If it finds one, the crawler will read that file first before continuing through the page.

Txt is case-sensitive: the file must be named “robots. This is especially common with more nefarious crawlers like malware robots or email address scrapers.

Txt to the end of any root domain to see that website’s directives (if that site has a robot. Each subdomain on a root domain uses separate robots.


It’s generally a best practice to indicate the location of any sitemaps associated with this domain at the bottom of the robots. Txt syntax can be thought of as the “language” of robots.

Allow (Only applicable for Google bot): The command to tell Google bot it can access a page or subfolder even though its parent page or subfolder may be disallowed. Note this command is only supported by Google, Ask, Bing, and Yahoo.

When it comes to the actual URLs to block or allow, robots. Txt files can get fairly complex as they allow the use of pattern-matching to cover a range of possible URL options.

Google offers a great list of possible pattern-matching syntax and examples here. But, they’ll only look for that file in one specific place: the main directory (typically your root domain or homepage).

Txt, it would not be discovered by user agents and thus the site would be treated as if it had no robots file at all. Txt file is found, always include it in your main directory or root domain.


Txt file or want to alter yours, creating one is a simple process. This blog post walks through some interactive examples.

Make sure you’re not blocking any content or sections of your website you want crawled. Txt, meta robots, or otherwise), the linked resources will not be crawled and may not be indexed.

If you have pages to which you want equity to be passed, use a different blocking mechanism other than robots. Txt to prevent sensitive data (like private user information) from appearing in SERP results.

Txt directives on your root domain or homepage), it may still get indexed. If you want to block your page from search results, use a different method like password protection or the no index meta directive.

Most user agents from the same search engine follow the same rules so there’s no need to specify directives for each of a search engine’s multiple crawlers, but having the ability to do so does allow you to fine-tune how your site content is crawled. If you change the file and want to update it more quickly than is occurring, you can submit your robots.

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Txt dictates site or directory-wide crawl behavior, whereas meta and x-robots can dictate indexation behavior at the individual page (or page element) level. Txt is a plain text file that follows the Robots Exclusion Standard.

Each rule blocks (or allows) access for a given crawler to a specified file path in that website. The user agent named “Google bot” crawler should not crawl the folder or any subdirectories.

Don't use a word processor; word processors often save files in a proprietary format and can add unexpected characters, such as curly quotes, which can cause problems for crawlers. Txt Tester tool to write or edit robots.

This tool enables you to test the syntax and behavior against your site. Txt file must be located at the root of the website host to which it applies.

For instance, to control crawling on all URLs below, the robots. If you're unsure about how to access your website root, or need permissions to do so, contact your web hosting service provider.

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If you can't access your website root, use an alternative blocking method such as meta tags. Txt file can apply to subdomains (for example, http://

Txt must be a UTF-8 encoded text file (which includes ASCII). Groups are processed from top to bottom, and a user agent can match only one rule set, which is the first, most-specific rule that matches a given user agent.

Supports the * wildcard for a path prefix, suffix, or entire string. Allow: A directory or page, relative to the root domain, that should be crawled by the user agent just mentioned.

Supports the * wildcard for a path prefix, suffix, or entire string. Must be a fully-qualified URL; Google doesn't assume or check HTTP/HTTPS/www.non-www alternates.

Keep in mind that in some situations URLs from the website may still be indexed, even if they haven't been crawled. Note: this does not match the various Abbot crawlers, which must be named explicitly.

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Txt to block access to private content: use proper authentication instead. Txt file might still be indexed without being crawled, and the robots.

This implementation hides your pages from search results, but the Mediapartners-Google web crawler can still analyze them to decide what ads to show visitors to your site. Match URLs that end with a specific string, use $.

For instance, the sample code blocks any URLs that end with .xls : Search engines robots are programs that visit your site and follow the links on it to learn about your pages.

The best way to edit it is to log in to your web host via a free FTP client like FileZilla, then edit the file with a text editor like Notepad (Windows) or TextEd it (Mac). If you don’t know how to login to your server via FTP, contact your web hosting company to ask for instructions.

The “Disallow: /” part means that it applies to your entire website. In effect, this will tell all robots and web crawlers that they are not allowed to access or crawl your site.

Important: Disallowing all robots on a live website can lead to your site being removed from search engines and can result in a loss of traffic and revenue. You exclude the files and folders that you don’t want to be accessed, everything else is considered to be allowed.

You can use the “Disallow:” command to block individual files and folders. You simply put a separate line for each file or folder that you want to disallow.

Txt file is telling bots that they can crawl everything except the /admin/ folder. The reason for this setting is that Google Search Console used to report an error if it wasn’t able to crawl the admin-ajax.php file.

This sitemap should contain a list of all the pages on your site, so it makes it easier for the web crawlers to find them all. If you want to block your entire site or specific pages from being shown in search engines like Google, then robots.

Search engines can still index files that are blocked by robots, they just won’t show some useful metadata. Source: Search Engine Roundtable If you hide a file or folder with robots.

Txt, but then someone links to it, Google is very likely to show it in the search results except without the description. On WordPress, if you go to Settings Reading and check “Discourage search engines from indexing this site” then a no index tag will be added to all your pages.

In most cases, no index is a better choice to block indexing than robots. In some cases, you may want to block your entire site from being accessed, both by bots and people.

It can be done with a free WordPress plugin called Password Protected. Txt file, especially abusive bots like those run by hackers looking for security vulnerabilities.

Txt file if they type it into their browser and may be able to figure out what you are trying to hide that way. Txt to the home page URL of your favorite websites.

Txt file is working, you can use Google Search Console to test it. Using it can be useful to block certain areas of your website, or to prevent certain bots from crawling your site.

Txt file, then be careful because a small mistake can have disastrous consequences. For example, if you misplace a single forward slash then it can block all robots and literally remove all of your search traffic until it gets fixed.

I have worked with a big site before that once accidentally put a “Disallow: /” into their live robots. They lost a lot of traffic and revenue from this small mistake.

WebKit (18,642,786) Blink (9,913,314) Trident (1,737,329) Presto (368,303) Gecko (299,203) Edge HTML (25,016) Gonna (3,639) HTML (3,483) Seafront (3,419) If you need to integrate the user agent parser directly into your website or system then it's very simple to use the API.

This will let you do things like advanced filtering and searching, identify trends in user agents, perform statistical analysis and other interesting applications.

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