Cached data is the culprit of low storage issues. Old iCloud backup: If you have iCloud backup turned on and iCloud storage is full, you will see the iPhone storage full message on your phone, even if there is nothing on your local iPhone or you deleted some large files just now.
Check the Recently Deleted Folder
This means that deleted data still exists on your phone—and is synced to iCloud—for some time, despite you having deleted it. People commonly forget to clear this album out since the folder is buried far down in the Photos app.
Cached Data: Sometimes, apps store temporary data or cache files on your phone's internal storage. Even if you delete files, these cached data may still occupy space. Clearing the cache of specific apps or using a cache cleaner app can help free up storage.
The first thing you can do is check how much storage space your apps are using. Some apps take up a lot of space; if you have many, they can quickly fill up your device. Delete the apps you don't use anymore or move them to your computer so you can still access them but they won't take up any space on your phone.
Empty Android's cached files
If you've deleted all the files you don't need and you're still receiving the “insufficient storage available” error message, you need to clear out Android's cache.
Your free space might actually be occupied by your operating system, so you may need to uninstall more apps to make more room. Use a cleaner app to free up space on your Android after you've done what you can but are still unable to make room.
Backups of your devices are often the culprits behind a full iCloud storage space. It's entirely possible you had your old iPhone set to upload backups to the cloud automatically, and then never removed those files.
Go to Settings > Security > Advanced and tap Encryption & credentials. Select Encrypt phone if the option isn't already enabled. Next, go to Settings > System > Advanced and tap Reset options. Select Erase all data (factory reset), and press Delete all data.
On an Android Phone, Go to Settings > Storage
If you drill down into the category, you can delete individual files or data. For example, under “Audio,” long-press on one or more files and tap Delete. Or under “Apps,” tap the app's name and then Uninstall to remove it from your phone.
Important: A factory reset erases all your data from your phone. If you're resetting to fix an issue, we recommend first trying other solutions. Learn how to troubleshoot Android issues. To restore your data after you reset your phone, you must enter security info.
Even though you have deleted the pictures from the iCloud photo library, they are not erased from your iPhone. They are transferred to another folder on your iPhone, called Recently Deleted. This causes the "iPhone photo storage full but no photos" issue.
Check other devices: If you're using iMessage on more than one device with the same Apple ID (like an iPad or Mac), the photos might be reappearing because they're not being deleted from those other devices. Try deleting the photos from all your devices.
When you tap Erase All Content and Settings, it completely erases your device, including any credit or debit cards you added for Apple Pay and any photos, contacts, music, or apps. It will also turn off iCloud, iMessage, FaceTime, Game Center, and other services.
A factory restore erases the information and settings on your iPhone, iPad, or iPod and installs the latest version of iOS, iPadOS, or iPod software.
Factory reset or hard reset deletes complete data and settings from your iPhone. All your photos, videos, contacts, call logs, passwords, messages, browsing history, calendar, chat history, notes, installed apps, etc., get deleted from the iOS device. It cleans your iPhone as new with no personal information at all.
If your device is almost full and can't free up space, you might get a Storage Almost Full alert. If you see this alert, check the storage recommendations or offload some less-used content like videos and apps.
Tap iCloud, then tap Manage Account Storage or Manage Storage. Or scroll down and tap Upgrade to iCloud+. Tap Buy More Storage or Change Storage Plan. Choose a plan and follow the onscreen instructions.
Find out what files are taking up space on Windows 10
Open Settings on Windows 10. Click on System. Click on Storage. Under the “(C:)” section, you will see what's taking up space on the main hard drive. Click the “Show more categories” option to view the storage usage from other file types.
Clean files and delete unwanted documents
File manager apps can help you to easily clean up your phone and create more storage space. These apps can scan your device to remove duplicate files, clean up your contact list, and identify apps you don't use that are hogging needed space.
Clear your Android storage in four easy steps
Go to your phone's Settings app. Tap Apps > See all apps. Now you can see each app's data information. Here, you can see how much space they're taking up.
Lots of Programs, Some Probably Unused
If you have a lot of programs installed on your computer, it can take up a significant amount of disk space. That is especially true for large programs that require a lot of storage, such as video games.