iOS available space doesn't add up Am I going mental, or does the number in the following image make no sense at all? my top 10 apps seem to account for barely ~15GB, so why is my used space so high?



So, I'm calling this a bug. The "other" section of my phone is taking up 40GB of space. I figured I'd just take a backup and restore my phone but due to there being no available space, I couldn't take a backup through iTunes. So I deleted my Spotify music, and the 40GB "other" grew almost instantly to take up the remainder of the space. I tried putting my phone into airplane more, but the button didn't put it into airplane mode - I had to restart and do it (I also temporarily lost use of my lock button and home button). I used a 3rd party tool to take a backup and deleted all my photos, and the storage has stopped growing at 42GB. Here's my iTunes screenshot for giggles:



I tried updating my iOS, nothing. I checked using iMazing at my phones directory structure (it allows you to view folder sizes) and none of my folders had 40GB, the total amounted to what my phone was reporting (~15GB).

I have no idea why it's doing it, so I'm going to go for a full restore from my newly created backup.
Is this device older than 2 years and has never been reset? 

I can't tell you exactly what to do but this article quotes some possible solutions:


Do you happen to send and receive a lot of messages with multimedia? that could be clogging up some of your storage especially if you set the settings to delete messages to never.
How much space do you seen take by the Other category? Other may include:


  If you've ever connected your iPhone to iTunes, you're well aware of the "other" stuff taking up space on your device. This data contains things like Safari's browser cache, your email, Siri's cache, reminders, notes, stocks, weather data, emails (including attachments), text messages, iMessages (including images and videos), app data, etc.



Check voicemails?
Try to reset Safari Cache and data.



EDIT: OP indicated that the issue is indeed with the "Other" category, this article has some tips on how to try and locate and free up space taken by various elements that make up this category.Also check this Apple forums thread. Download any mentioned software there after doing your own DD.

Here's what "Other" includes, in full:


  Browser cache
  
  Mail cache
  
  Mail messages
  
  Mail attachments
  
  Safari's Reading List
  
  iTunes Backups
  
  Crud resulting from jailbreaking your iDevice
  
  Game data
  
  Saved data files
  
  Call history
  
  Notes
  
  Media
  
  Voice memos