Firefox is an open-sourced, cross-platform web browser developed by Mozilla Foundation, designed for the modern-day Internet users and applications that dominate the web. Firefox is written in C++/C and contains over 2400 kLOC (Grosskurth et al, 2003). It is available for all major operating systems in over 96 languages. Firefox was first released back on Nov 9, 2004, as part of the Mozilla project, with the goal of providing users with the best browsing experience whilst putting the user in control. The system architecture of Firefox is similar to most modern web browsers which follow the layered architecture whereby each layer below provides services to the upper layer. The architecture of Firefox follows the layered architecture with the NSPR layer (Netscape Portable Runtime) at the bottom which interacts with Operating Systems. In this report, we present an analysis of the Firefox web browser. The goal of this paper is to present findings on Firefox's software architecture, its quality attributes and analysis models. This paper seeks to further understand the details and design choices used by the Mozilla team when creating Firefox. The methodology used to arrive at an accurate and correct architecture was to first read and investigate into 2 primary web browsers of Chrome and Safari to get a fundamental understanding of the general structure for a mature web browser. For further confirmation, Mozilla documentation about the functionality of each subsystem was used. This was in addition to corroboration and correlation of the inner components with the source code.