How Web Browsers Work: Firefox, Chromium and Safari Compared

Summary: The supplied article explains how web browsers work by comparing Safari, Firefox, and Chromium, focusing on their browser engines, JavaScript engines, features, performance, compatibility, privacy, and use cases. It states that Safari uses WebKit and JavaScriptCore, Firefox uses Gecko and SpiderMonkey, while Chromium uses Blink and V8. The article discusses practical browser-selection considerations, including Firefox’s emphasis on privacy and customization, Chromium’s broad website compatibility and ecosystem, and Safari’s battery efficiency and Apple hardware integration. It notes that some websites and services are optimized for Chromium, citing YouTube as a documented historical example and referring to Excalidraw, Squoosh, and Google Meet as services that lean on Chromium capabilities. It also describes Firefox extensions such as “Chrome Mask” and “Open in Google Chrome Browser.” The article explains that JavaScriptCore, SpiderMonkey, and V8 execute the same JavaScript language while using different implementations and optimization approaches. It further compares their parsing, bytecode, interpretation, JIT compilation, memory management, WebAssembly, security, debugging, performance, ecosystem, internal pipelines, and design philosophies.

How a Web Browser Works

What it is

a. Today, the way GUI (Graphic User Interface) of various applications is being developed, a web browser will rank among the top 5. Practically everybody is using one or the other web browser.

b. The author tries to analyse as to “how a web browser works”. To achieve the objective, I intend to proceed in a comparison manner of following three web browsers. It will enable the audience to choose the one as per their needs.

c. Before proceeding, one may usefully refer to https://www.webbrowserdirectory.com/browsers/

d. One may also usefully refer to https://zen-browser.app/, a Firefox based web browser. It is being recommended for its variety of features.

Why this article

e. When the season of Income Tax Return of non-business no audit with July 31, 2026 as due date was on, my office’s Income Tax return Application is integrated with Google Chrome Browser. The Google Chrome was opening 16-20 threads, and it is reducing the overall speed and at times the machine hangs.

f. I kept the Google Chrome as default browser but instructed the staff to use Microsoft Edge and / or Mozilla Firefox for other purposes. Though not 100%, it solved the issue and it made me think as to what happened.

g. It ignited a curiosity as to why such a phenomenon. In that period, there were multiple things that were happening including the development of Google-Chrome Web Browser. There were news items that Google-Chrome Web Browser was installing a 1.5 GB size file for AI.

Take away Point

h. In general, public at large will be using either Firefox or chromium (or variant thereof)

a. Firefox = focuses more on security

b. Chromium = focuses more on speed.

i. The above is a very broad statement. There are some websites which are specifically optimised for chromium-based web browsers. For those websites, chromium-based web browser will give better results.

j. For using any service from Google ecosystem, obviously, it is advisable to use a browser based on chromium

Real, citable example — a site favouring Chrome

k. The clearest documented case is YouTube. In 2018, a Mozilla engineer pointed out that YouTube’s redesign relied on a deprecated web technology (Shadow DOM v0) that only Chrome had implemented, and this made the site around five times slower on Microsoft Edge and Firefox at the time.

l. It’s an old story now and the specific bug has since been fixed, but it’s a real, widely-reported example you can point to: com, circa 2018, running noticeably worse on non-Chrome browsers because of a technical choice Google made.

Lean on chromium-based browser

m. Refer to the following websites one can open today that lean on Chrome-only capabilities. This is not a criticism (not controversial — just genuine feature gaps)

a. excalidraw.com — the “save to disk” / “open from disk” flow uses a Chromium-only API (File System Access). On Firefox it still works, just falls back to a plain download instead of live-editing a file on your computer.

b. squoosh.app — Google’s own image-compression tool, built to lean on Chromium’s fastest image codecs.

c. meet.google.com— Google has long recommended Chrome for the best video quality and background-blur performance; other browsers work but with more limited feature sets.

Extension namely “Chrome Mask,” in Firefox

n. A little Firefox Extension that provides a one-click toggle to spoof as Chrome in Firefox – or, in other words, to put on the Chrome Mask. There are a lot of generic “User Agent spoof” extensions. However, this extension does a few things differently:

o. Instead of overriding the User Agent string on all sites, this extension allows you to only look like Chrome on specific sites.

p. Unlike some extensions with outdated version numbers and UA strings, this extension automatically updates the Chrome version it pretends to be. It does that by querying a simple API every 24 hours.

q. You don’t have to pick the correct Operating System manually; this extension does it for you.

r. Even if you do not understand the following technical thing, it is perfectly alright.

Another Extension namely “Open in Google Chrome Browser” by Andy Portmen

s. In this case, it opens the current tab or links in the Google Chrome browser. Using this extension, you can send links to Google Chrome without the need to manually copy and paste links. It is even possible to define keyboard shortcuts for easier access.

Summary-:

t. The author could not find websites which lean towards Firefox as compared to chromium. The reason being the structure of firefox is asymmetric, i.e. it caters to a variety of users and a variety of purposes of browsing. It tries to accommodate every such permutation and combination whereby the users’ objective is served.

u. It tries to ensure that every user is able to accomplish their objective irrespective of the way in which a particular website is structured.

v. Another practical reason is that google has an eco-system which Firefox (Mozilla) does not have.

Browser Engine and Feature Comparison

Car Analogy

w. Every web browser can be divided broadly in two parts namely

a. an engine

b. other browsing features

x. Taking the above analogy slightly ahead, the driver never directly interacts with the engine.

y. The names of the cars and their features are used only for illustration. It does not intend to mean verbatim i.e. do not think that because BMW is better than Mercedes, so consequentially Firefox is better than Chromium.

z. The driver never directly interacts with the engine. Likewise, a browser user rarely interacts directly with WebKit, Gecko, or Blink.

Scope of the article

aa. Broadly speaking, following are the popular one and perhaps different ones the analysis of which will be useful.

a. Safari = Only on Mac machines or Mac Environment like i-phone, iPad. People would have heard about it but might not have worked on it. It is highly optimised with Apple’s hardware but it does not work on other operating systems and / or devices.

As contrary to above, the following works on every device and / or every operating system.

b. Firefox = Mozilla Foundation (non-profit) and Mozilla Corporation (commercial subsidiary). Other based on this are Firefox ESR, Tor Browser. com

c. Chromium = serves as the base for browsers such as Google Chrome, Microsoft Edge, Brave, Opera, and Vivaldi. org

Other Features

Perceiving repetition for all features…? Most obvious question Are JavaScriptCore, SpiderMonkey, and V8 different programming languages? The answer is ‘No’. They all execute the same JavaScript language but in their own manner.

Some other related things

Overall Features

Rendering Engine Comparison

Which One Should You Choose?

Overall Assessment

JavaScript Engine Comparison

For those interested in technical aspects or respective engines

Below is a comparison of the three JavaScript engines from an engineering perspective. All three implement the ECMAScript (JavaScript) standard, but their internal designs and optimizations differ.

Summary

1. JavaScript Parsing

2. Intermediate Representation

3. Interpreter

4. Just-In-Time (JIT) Compilation

5. Memory Management

6. Optimization Techniques

7. ECMAScript Support

8. WebAssembly

9. Multithreading

10. Debugging Support

11. Security Features

12. Performance Characteristics

13. Ecosystem

14. Internal Pipeline

15. Design Philosophy