What is the difference between a browser engine, a rendering engine, and a user agent?

Question

What is the role of the user agent switch?

https://addons.mozilla.org/en-US/firefox/addon/59

Is the user agent different from the rendering engine?

If the browser uses the same rendering engine, do we need to check each browser?

Answer 1

• The rendering engine is the engine that the browser uses to render html (i.e. gecko vs webkit).
• A user agent is how the browser identifies itself (e.g. firefox 3.5).

But even if you switch the user agent, say firefox for safari, it will still use the gecko rendering engine to render its page.

So, to check how the page is displayed in different browsers, you really need to display the page in these different browsers.

Answer 2

A user agent is a string that a browser sends in HTTP headers to identify itself. Thus, different sites distinguish between IE, FireFox / Mozilla, Safari / Webkit, etc.

The user agent informs the site of the rendered rendering engine, but it is not a rendering engine itself.

Wikipedia

Answer 3

Some websites display content differently according to the agent submitted by the user. For example, if the user agent is IE 6, the language used to render the web page (e.g. PHP) can be used to add a class to the element, that is, CSS, and then use CSS to control what is displayed or not. Or a separate user file may be added depending on the user agent.

Several years ago, Opera recommended installing the User Agent as IE 6, because websites would not be displayed consistently if the user agent was not one of IE or Mozilla. But, I think, this is no longer the case.

Answer 4

The role of the User Agent Switcher is to basically switch one browser to another browser called User Agent. This determines the entire language on the server side, with the help of which access to their application, as well as to the device, etc.

What does Wikipedia say about the user agent?

When a software agent runs on a network protocol, it often identifies itself, its type of application, operating system, software vendor, or software version.

Take a look at the Browser Arch and a list of engines for each browser.

Browser architecture

Browser List>

What is rendering?

• A layout / rendering engine that can display the contents of a given URL in a browser screen and interprets HTML, XML and CSS.
• It is single threaded. Default.
• It displays data according to the specified content type (MIME). For example, HTML, images, XML, CSS, JSON, PDF, etc.

Click here to refer to my article to understand what is behind the browser. https://medium.com/@ramsunvtech/behind-browser-basics-part-1-b733e9f3c0e6

Answer 5

• User agent is software acting on behalf of a user.
• A A rendering engine is software used by a browser to display markup code.

The user / client can change the user agent for the browser. Where, as the browser does the markup code, does not change.