How can I free up space on my iPad to update or back it up?

The general consensus, based upon many years of experience, is that you should aim to maintain at least 4-6GB of available free space for iPadOS to use for temporary storage.

This is particularly important when performing an OTA system software update - as there must be adequate free-space in which to download, unpack and verify an update prior to installation. As soon as the update has been successfully installed, the OS will automatically clean-up temporary files - releasing this space to the system as free-space. Major version updates require considerably more temporary space than smaller point-updates.

If you are short of space, you can selectively offload Apps. Offloading Apps removes just the Apps themselves - but preserves the associated App data and settings. Apps are typically only offloaded to provide additional temporary storage space - so as to perform a system software update where available storage in insufficient. Subsequent access will cause the offloaded App to automatically reinstall.

https://9to5mac.com/2020/01/21/how-to-offload-apps-in-ios-to-save-space-without-deleting-their-data/

By contrast, deleting an App from the iPad removes both the App and the associated user-data. Unless this data has been backed-up elsewhere, the associated data will be lost.

An alternative strategy where space is short is to perform the update using a Windows PC (with iTunes for Windows installed, or more recent Apple Devices App) or a Mac computer (with iTunes or Finder - as appropriate for the installed version of macOS) to perform the update. Here the update package is downloaded, unpacked and verified on the computer - before the update is installed by the computer on the target device. Notwithstanding the general recommendation to maintain at least 4-6GB of free-space on the iPad, this method requires considerably less free-space to successfully install an OS update on a space-constrained device.

Additional information about creating sufficient space for installation of a software update can be found here:

If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support

LexiCullen101 wrote:

I have not turned on my 7th gen iPad in a long while. When I did, I realized I needed to update it. I just barely did not have enough space to update it, so I had to plug it into my PC to update it. Now, 20gb is being taken up on my iPad by OS and System Data. I want to reset my iPad to see if this helps at all. When I try to back it up to iCloud on the iPad, I'm told I don't have enough space to do so. When I plug it into my PC, no matter if I choose iCloud or local backup, I'm told iTunes could not backup the iPad because the iPad disconnected - despite it very clearly being still connected. I've tried multiple cords and multiple ports. I've restarted my iPad. I'm on OS 18.5, and have 32gb with 31.83 being used. I need either help backing it up, or if someone can help me figure out why the heck 2/3 of my storage is being taken up not by me, that would be great.

Purchase more icloud storage so you can back up to the cloud.