Google Drive Offline Document File Location

On my computer (Windows 8.1 / Chrome version 41.0.2272.101 m) I found the filesystem at "C:\Users\my username\Appdata\Local\Google\Chrome\User Data\Profile 1\File System"

I needed to find it because I had some corrupted images in Google Slides (they worked on other computers or other browsers on my computer, just not in chrome on my computer). I deleted the File System directory and shazam, the images reloaded and were no longer corrupted.

Further, it may interest you, the location where Google Drive stores offline docs in Android's file system.

sdcard/android/data/com.google.android.apps.docs/

Google Drive uses Chrome's IndexedDB for storing data about files. To see the contents, open developer console (Ctrl + Shift + I) and choose Resources tab.

This answer tells you about actual location of IndexedDB in the file system on Windows.

On Linux it's: ~/.config/google-chrome/Default/IndexedDB

It turns out the offline documents are stored in the HTML5 FileSystem.

The Chrome FileSystem storage is located here on my Windows 7 machine:

C:\Users\<username>\AppData\Local\Google\Chrome\User Data\Default\File System

I added a number of large images to a document with the Chrome "Offline Docs" enabled and was able to see the FileSystem storage directory grow appropriately.

I then used the HTML5 FileSystem Explorer extension for Chrome to view the file structure of an offline document and was able to confirm that the images were, indeed being retrieved from the HTML5 FileSystem when Chrome was offline. See screenshot: