【Reducing File Size】

1、Unity strips out unused assets。

　　The amount of assets in your project folder does not influence the size of your built player. Unity is very smart about detecting which assets are used in your game and which are not. Unity follows all references to assets before building a game and generates a list of assets that need to be included in the game. Thus you can safely keep unused assets in your project folder.

2、Optimizing mesh and animation size。

　　Meshes and imported Animation Clips can be compressed so they take up less space in your game file. Compression can be turned on in Mesh Import Settings.

　　Mesh压缩会使数据的准确性降低。Note that mesh compression only produces smaller data files, and does not use less memory at run time. Animation Keyframe reduction produces smaller data files and uses less memory at run time, and generally you should always use keyframe reduction.

3、Unity prints an overview of the used file size

　　After Unity has completed building a player, it prints an overview of what type of asset took up the most file size, and it prints which assets were included in the build. To see it just open the editor console log: Open Editor Log button in the Console window (Window -> Console).

　　当Unity构建完一个版本，会打印出各种资源的的硬盘花费，以有打印出哪些内容在硬盘中。在Unity中的Console下右键，选择Open Editor Log即可。

参考：file://localhost/Applications/Unity/Unity.app/Contents/Documentation/html/en/Manual/ReducingFilesize.html

Reducing File Size