Unveiling the true drivers of Windows 11's growth

The installation size for Windows continues to expand. The 23H2 version already weighs around 6.3GB, with the test Canary version even larger. While a proliferation of theories has risen to explain this growth, a close analysis reveals most of these to be unfounded.

To accurately identify the causes for this system size increase, it's crucial to look not just at the ISO files, but the content of WIM files contained within the ISOs. These files store the image written to the disk during installation. By comparing install.wim files from Windows 10 and Windows 11, we find that the size of the new system is approximately 121% of Windows 10. However, manually inspecting the file directories allows us to identify the specific components contributing most to this size increase. For instance, the Program Files directories have collectively grown by about 0.66GB. But why?

Surprisingly, despite a reduction in the size of system applications, the directory has swelled due to one key player - Edge. Microsoft's Edge browser, previously included as a single instance in Windows 10, now makes three appearances in Windows 11: as Edge, EdgeCore, and EdgeWebView. The latter two are embedded programming components that many modern applications require, even for Windows 10. This means that the main difference is not in the installed system size, but rather in the installer's size.

In addition, the Windows directory itself has broadened by approximately 2.31GB due to the expansion of the component warehouse, or WinSxS, which now takes up an extra 1.22GB; 0.65GB of this is once again attributed to Edge. CBS is the second-largest contributor to WinSxS. Not counting these two elements, the size increase for WinSxS between Windows 10 and 11 is a modest 4% - an acceptable change over more than three years.

However, WinSxS's growth only accounts for half of the total size discrepancy between systems. The remaining 1.22GB can be traced to the System32 directory which, partly due to a more advanced and secure recovery environment (Windows RE), has significantly increased in size. This recovery environment, not the primary system, launches during automatic repairs, BitLocker recovery, and other system failures.

Another 0.5GB is occupied by...you guessed it: a fourth copy of Microsoft Edge, this time included as a system rather than a WebView application, delivered separately for compatibility. The final 0.11GB is consumed by drivers for devices that have been released between the launch of Windows 10 and 11. Outside of this, growth of the System32 directory from 10 to 11 is only a 3%, lower than that of WinSxS.

All other directories continue this trend, with average growth in file size ranging from 2 to 5%. These minimal changes demonstrate that the majority of Windows has maintained a similar size for years. The real size differences only become apparent when comparing older systems such as Windows 8.1, where the WinSxS directory is 37% larger and System32 is 50% bigger.

Discounting Edge, these figures drop to 25% and 31% respectively. Tracing back even further to Vista (the first system distributed in WIM files), we see an increase in WinSxS by 50% and System32 by 70%, but excluding Edge, the figures are 41% and 50% respectively. This shows the rate of Windows' size increase has significantly slowed, not escalated.

The primary catalyst for Windows' size change is Edge. Mechanisms such as WebView and applications using similar concepts, like Electron, have exponentially increased the number of internet browser engines on an average computer. Ultimately, this leads us to conclude that the primary driver behind software size inflation today is not .NET, XAML, UWP, WinUI 3, or supposed quality decline in internal Windows components, but rather... Chromium.