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User Agent

Last updated: Oct 07, 2022

https://cmlabs.co/en-vn/seo-terms/user-agent

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What is a User Agent?

A user agent is a piece of software that retrieves, renders, and facilitates interaction between end users and website content. Its role is to be the mediator that communicates end-user requests to the server.

An example of a user agent, or UA, is a browser that retrieves website content on a server and displays it to the user. The way it works is to process user instructions, transfer them to the server, and receive the requested data from the server.

User Agents in HTTP Header

When communicating with the server, the UA will provide information regarding its identity or characteristics. The information provided is the software name, software version, operating system, device model, software vendor, software revision, and others. This information is delivered to the server in the form of a string in the HTTP request header.

The string function of the agent is to negotiate content with the server. That is, the server will use the information in the string to assess its capabilities and provide data accordingly.

An Example of User Agent String

To easily understand the form of the string in the HTTP request header, you can see the example of the syntax below. You need to remember that each agent has a different string and information content. Check out the example of the string below:

Mozilla/5.0 (Linux; Android 6.0.1; Nexus 5X Build/MMB29P) AppleWebKit/531.21.10 (KHTML, like Gecko) Chrome/79.0.3945.136 Mobile Safari/537.36

The following describes each component in the UA string:

Mozilla/5.0: Product name and version.
Linux; Android 6.0.1; Nexus 5X Build/MMB29P: Details of the device and operating system.
AppleWebKit/531.21.10: The rendering engine used.
KHTML, like Gecko: Details of the rendering engine.
Chrome/79.0.3945.136: browser type and version number.
Mobile Safari/537.36: a browser that acts like Safari with version number 537.36.

Based on the example above, the agent tells the server that the user's instructions come from the Android device so that the server will send the website display with the mobile version to the user.

The information contained in the string can also be used as user data that is stored on the server and used for audience analysis purposes.

Types of User Agents

As explained earlier, user agents are browsers used by users, such as Google Chrome, Mozilla Firefox, Safari, Opera, and so on. In addition to the browser, there are several other pieces of software that are considered user agents, which are:

SEO tools (Example: SeobilityBot)
Web crawler (Example: Googlebot, Yahoo! Slurp, MSN bot)
Link checker (Example: W3C-Checklink)
Legacy operating systems (Example: AmigaVoyager)
Game console (Example: PlayStation, Wii, PlayStation Portable)
Web applications (Example: Flash Player, screen readers, validators, media players, streaming portals)

How to Change User Agents

After understanding all there is to know about user agents, you may wonder “what is my user agent?”. The identity is not easy to define because it is given by your browser. Nevertheless, you can also change it.

You can change the string by performing spoofing. This process will cause your UA to send a string with information that does not match the original. This action is harmless and can actually help you as an SEO professional.

The purpose of spoofing is to identify any cloaking problems on the website. Cloaking is the condition when a website displays different content to Googlebot or other users.

This condition is considered by Google as a violation and is included in the black hat SEO category. By doing spoofing, you can identify cloaking on the website.

How to Change User Agents on Chrome and Edge

Right-click on the website page, then select 'Inspect'.
Click the three vertical dots in the upper right, select 'More Tools', then select 'Network Conditions'.
In the user agent section, remove the 'Select Automatically' checklist.
Select the agent that you want to use.
If there is no agent you want to use, you can write the string yourself.

How to Change User Agents on Safari

On the 'Safari' menu, select 'Preferences'.
Go to the 'Advanced' section and check the 'Show develop menu in menu bar' section.
Next, open the 'Develop' menu and select 'User Agent'.
Select the agent that you want to use.
Select 'Other' to write your own string.

How to Change User Agents on Firefox

Download and install the Firefox add-on called User Agent Switcher.
Once the add-on is downloaded, you will see the add-on icon at the top right of the browser.
Click the icon, then you can choose the user agent you want to use.
If there is no agent you want to use, you can use the custom feature.