Browsers & How do they work?
General Overview
The main function of a browser is to present the web resource you choose, by requesting it from the server and displaying it in the browser window. The resource is usually an HTML document, but may also be a PDF, image, or some other type of content. The location of the resource is specified by the user using a URI (Uniform Resource Identifier).
The browser's high-level structure
The browser's main components are:
The user interface: this includes the address bar, back/forward button, bookmarking menu, etc. Every part of the browser display except the window where you see the requested page.
The browser engine: marshals actions between the UI and the rendering engine.
The rendering engine: responsible for displaying requested content. For example, if the requested content is HTML, the rendering engine parses HTML and CSS and displays the parsed content on the screen.
Networking: for network calls such as HTTP requests, using different implementations for different platforms behind a platform-independent interface.
UI backend: 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 parse and execute JavaScript code.
Data storage. This is a persistence layer. The browser may need to save all sorts of data locally, such as cookies. Browsers also support storage mechanisms such as localStorage, IndexedDB, WebSQL, and FileSystem.
Role of Rendering Engine
Once a user requests a particular document, the rendering engine starts fetching the content of the requested document. This is done via the networking layer. The rendering engine starts receiving the content of that specific document in chunks of 8 KBs from the networking layer. After this, the basic flow of the rendering engine begins.
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