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 String Length

Bob Roberts
• Monday, 05 October, 2020
• 11 min read

HTTP's specification does not limit length of headers at all. However, web-servers do limit header size they accept, throwing 413 Entity Too Large if it exceeds.

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Use a dedicated table to store only Reagents (normalize it) In your related tables, store a Foreign Key value to point back to the Sergeant auto-increment primary key field Store the actual Sergeant string in a TEXT field and care not about the length Have another UNIQUE BINARY(32) (or 64, or 128 depending on your hash length) and hash the Sergeant Also enforce a maximum length in your INSERTer to keep UA strings it under 4 KB.

Coventry CodeAngry11.6k33 gold badges4242 silver badges5050 bronze badges It looks abnormal to me but I regularly see such things in logs mostly from Windows systems.

Harry harry93111 gold badge1111 silver badges1313 bronze badges Since it's for database purposes and there is no practical limit I'd go for a Reagents Table with UserAgentId as Int and UserAgentString as NASCAR(MAX) and use a foreign key on the original table.

Assume the useragentstring has no limit on its length and prepare to store such a value. In Postgres, there's a text type that accepts strings of unlimited length.

Note that platform can consist of multiple ; “-separated tokens. Rv: gecko version indicates the release version of Gecko (such as 17.0 “).

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For compatibility, it adds strings like HTML, like Gecko and Safari. The Opera browser is also based on the Blink engine, which is why it almost looks the same, but adds “Or/”.

In this example, the useragentstring is mobile Safari’s version. An user agent (UA) string is able to be used to detect what version of a specific browser is being used on a certain operating system.

Mapping UA string tokens to a more human-readable browser name for use in code is a common pattern on the web today. When mapping the new Edge token to a browser name, Microsoft recommends using a different name than the one developer used for the legacy version of Microsoft Edge to avoid accidentally applying any legacy workarounds that are not applicable to Chromium-based browsers.

When Microsoft is notified about these types of issues, website owners are contacted and informed about the updated UA. In these cases, Microsoft uses a list of UA overrides in our Beta and Stable channels to maximize compatibility for users who access these sites.

One of the things I'd said I'd do, Dear Reader, when I went to work for the Big Blue Monster, was to get your feedback into The Company whenever possible. In the process I've gotten to see a LOT of interesting Browser Reagents in the IIS logs.

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If you visit the site and scroll down, you'll see YOUR Browser Sergeant at the bottom. However, there's other stuff in there, like I have the June software, I have Media Center enabled, and I've got three versions of the .NET Framework.

Now, this guy is clearly a developer who has installed beta versions of things, but he's also got Inflate and a bunch of other stuff. Still, that's a pretty crazy Sergeant and it's being transmitted all the time.

What if the values were conflated to show just the major side-by-side CLR releases? About Scott Hansel man is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee.

He is a failed stand-up comic, a cornrowed, and a book author. You may have reached us looking for answers to questions like: How to find the useragentstring.

Device Atlas Cloud offer a great way to start detecting mobile device traffic to your site: When a software agent operates in a network protocol, it often identifies itself, its application type, operating system, software vendor, or software revision, by submitting a characteristic identification string to its operating peer.


During the first browser war, many web servers were configured to send web pages that required advanced features, including frames, to clients that were identified as some version of Mozilla only. Other browsers were considered to be older products such as Mosaic, Cello, or Samba, and would be sent a bare-bones HTML document.

Automated web crawling tools can use a simplified form, where an important field is contact information in case of problems. Automated agents are expected to follow rules in a special file called robots.txt “.

The popularity of various Web browser products has varied throughout the Web's history, and this has influenced the design of websites in such a way that websites are sometimes designed to work well only with particular browsers, rather than according to uniform standards by the World Wide Web Consortium (W3C) or the Internet Engineering Task Force (IETF). Websites often include code to detect browser version to adjust the page design sent according to the useragentstring received.

Thus, various browsers have a feature to cloak or spoof their identification to force certain server-side content. For example, the Android browser identifies itself as Safari (among other things) in order to aid compatibility.

User agent sniffing is the practice of websites showing different or adjusted content when viewed with certain user agents. An example of this is Microsoft Exchange Server 2003's Outlook Web Access feature.

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When viewed with Internet Explorer 6 or newer, more functionality is displayed compared to the same page in any other browsers. Web browsers created in the United States, such as Netscape Navigator and Internet Explorer, previously used the letters U, I, and N to specify the encryption strength in the useragentstring.

Until 1996, when the United States government disallowed encryption with keys longer than 40 bits to be exported, vendors shipped various browser versions with different encryption strengths. Following the lifting of export restrictions, most vendors supported 256-bit encryption.

I've been rejected until I come back with Netscape” ^ “Android Browser Reports Itself as Apple Safari”. ^ User Agent String explained: Android WebKit Browser”.

A UA string is a piece of text that browsers send to websites when they initiate a connection. The UA string contains details about the browser type, rendering engine, and operating system.

For decades, websites have used UA strings to fine-tune features based on a visitor's technical specifications. For starters, UA strings have been used by online advertisers as a way to track and fingerprint website visitors.

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To address these issues, Google said it plans to phase out the importance of UA strings in Chrome by freezing the standard as a whole. The long-term plan is to unify all Chrome UA strings into generic values that don't reveal too much information about a user.

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.

Botenvouwer botenvouwer3,44877 gold badges3838 silver badges6565 bronze badges Mozilla is a browser rendering engine (the one at the core of Firefox) and the fact that Chrome and IE contain the string Mozilla/4 or /5 identifies them as being compatible with that rendering engine.

Visit that page, it'll give you a good explanation of each element of your user agent. Claims to be a Mozilla based user agent, which is only true for Gecko browsers like Firefox and Netscape.

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