Browsers
Any application can make requests using the HTTP protocol. However, web browsers are applications whose primary purpose is to request data using HTTP, format the content, and display it on screen. That content is normally defined using the HTML format, and the appearance of the content is defined using CSS.
A browser's implementation can be divided into several areas:
- The networking logic that is used to request data
- The rendering engine that parses fetched content, determines how it should be laid out on screen, processes the styling rules, and actually draws the pixels on screen
- A JavaScript engine that parses and executes JS code
- The browser chrome that defines the visible UI around the page content (buttons, menus, address bar, etc)
Different browser implementations may share and reuse implementation pieces, but use their own unique implementations for other sections. For example, several browsers are built on top of the "Blink" rendering engine, like Chrome and Edge, but have very different UI implementations and user-visible features.
Browser Notes
Some notes on the major browsers:
Chrome:
Built on an open-source core called "Chromium", which is effectively Chrome minus all the actual Google account integration and branding
The "Chrome" browser partly got its name because it tried to minimize the amount of "browser chrome" (the term for all the browser UI that surrounds the actual page content)
Google has a tendency to announce new web features that only exist in Chrome and yet consider them "final" even if other browsers haven't added them yet
Safari:
The only actual browser rendering engine allowed by Apple on iOS devices. Any other browsers you see on iOS are actually the Safari core with a different UI skin and branding.
Apple tends to be slow adding new features to Safari even after they've been added to other browsers. Apple has also refused to add certain features on the grounds that they might make act as privacy leaks in some way.
Firefox:
Open-source, and built by the Mozilla organization - it's the only major browser not built by one of the big tech companies Now that many browsers build on top of Chromium/Blink or Webkit, Firefox's "Gecko" engine is the main alternative rendering engine still in meaningful use.
Edge:
There's been two different variations of the MS Edge browser. The first was actually built entirely by Microsoft, using a cleaned-up and modernized version of the rendering engine previously used in Internet Explorer. Recently, Microsoft stopped developing their own rendering engine, labeled that version of Edge as "legacy", and rebuilt Edge on top of Chromium with their own UI.
Internet Explorer:
IE was the default browser on Windows up until recently. Many companies still have internal websites that only work correctly in IE, which keeps it as a small but persistent portion of the market.
IE has "stagnated" twice. IE6 came out in 2001 along with Windows XP, but Microsoft stopped developing it for several years until Firefox and Chrome began taking away market share. Today, IE11 is considered an obsolete browser without many modern capabilities, and many companies are finally dropping support for running their sites in IE11.