What is a Web Browser

The main function of a browser is to present the web resource, by allowing a user to request it from the server and then display it in the browser window. The resource is usually an HTML document, but may also be a PDF, image, or some other file type. The location of the resource is specified by the user using a URI/URL (Uniform Resource Identifier/ Uniform Resource Locator).

A typical webpage is based on its HTML for content, CSS (Cascading Style Sheets) for how that content looks and JS (Javascript) for interactivity.

A typical flow is the user inputs, sends a URL request or search query, the server responds so the browser prepares to render the result, get the result and render the resource

The user interface (UI)

This UI includes the address bar, back/forward button, bookmarking menu, settings, etc. Every part of the browser display except the requested page.

The browser engine

Allows for the user interface to interact with the rendering engine.

The rendering engine

The rendering engine for displaying requested content. If the resource is a webpage the rendering engine parses HTML and CSS, and displays the page on the screen.

Networking

Allow for network calls such as HTTP requests and API calls, using different implementations for different platforms behind a platform-independent interface.

UI backend

UI backend is used for drawing basic widgets like combo boxes and windows. This backend exposes a generic interface that is not platform specific. Underneath it uses operating system user interface methods.

JavaScript interpreter

Used to read and run JavaScript code. JS allows runs client side to allow webpages to be interactive.

Data storage

Data can be stored locally. An example is cookies which are used to identify your computer as you use the internet. Browsers also support storage mechanisms such as localStorage, IndexedDB, WebSQL and FileSystem.

Based on https://gs.statcounter.com/browser-market-share as of December 2022, the worldwide market share for browsers is as follows.

Chrome	64.68%
Safari	18.29%
Edge	4.23%
Samsung Internet	3.05%
Firefox	3.01%
Opera	2.25%

Web Browsers