I have an HTC One with an internal storage of 3.85 GB, but according to my Apps page, I'm using 3.63 GB of that space. My Android version is 4.1.2. I tried to install an app today, but it wouldn't install because there wasn't enough space. This was the first time I noticed this was a problem. I have very few apps on my phone besides the pre-installed ones. All together, the apps themselves add up to about 900 MB, and I've gone through the cache and application data on every app that I think might store any significant data, but none have used up enough space to explain why I'm missing so much. In order to browse the filesystem, I installed a file explorer app (ES File Explorer), but when that app calculates the available space on the phone, it claims that only about 900 MB have been taken up. Is this some kind of error on the phone where it thinks it's full but it isn't, or is it most likely space being taken up in some obscure part of the phone? Any suggestions on how I can find this data to delete it?