An interesting point:
Aaaaa! Is a great test case for a worst case scenario when it comes to file size. We have a game with over 200 levels or zones, over with 300 level assets that can be spawned at runtime in any level, 48 unique skyboxes (6 textures per sky!), and 38 full-length songs. Our standalone PC/Mac build weighs in at 388mb uncompressed. Downloading almost 400 megabytes to get to the title screen of our game would be completely unacceptable!
In our case, we were able to rely on Unity’s build process to efficiently strip and pack the build into a much smaller size, but also took advantage of Unity’s AudioClip streaming solution to stream in our music at runtime on demand! The file size savings of streaming music was huge and highly recommended for all Unity games. To glean additional file size savings, Asset Bundles can be used for loading levels on demand, but are best used in simple games or when building games from the ground up with web in mind.
In the end, our final *compressed* WebGL build size, which includes all of our loaded assets as well as the Unity engine itself ended up weighing in at 68.8 MB, compared to a *compressed* standalone size of 192 MB, almost 3x smaller than our PC build!