It's comprised of system caches, logs, Siri voices (if you've downloaded more than one), updates, and so much more. One of the biggest culprits for Other/System Data growing out of hand is streaming lots of music and video.
Remove videos, books, and music stored on your phone
Sometimes what's taking up the most amount of storage are the data and documents stored within an app on your phone. You can find out if that's the case by once again heading to Settings > General > iPhone Storage and then clicking on an app.
It could be that your iPhone has accumulated cache files over a period of time and those caches have now become too large for your iPhone to handle. In this case, what you can do is to clear the cache files for the Safari browser on your iPhone to free up memory space.
Photos are among the biggest offenders when it comes to gobbling up space on your iPhone. But the iPhone's settings menu has an option that enables your device to save smaller photo files locally if your device is low on space instead of the original versions.
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.
If you're seeing an "Insufficient storage available" message on your Android, chances are that you've used up most of your device's available memory. To fix this, you'll need to make some space by deleting apps and/or media; you can also add external storage, such as a Micro SD card, to your phone.
Solution 1: Clear App Cache to Free up Space on Android
In general, the lack of working space is probably the main cause of having insufficient storage available for Android users. Usually, any Android app uses three sets of storage for the app itself, the app's data files and the app's cache.
Clearing your cache removes stored data that helps websites and apps open faster, while offloading temporarily uninstalls an app without deleting any of the documents and data associated with that app. Both methods can help speed up iPhones that are slowed down by low storage.
Your iPhone memory is full and you can no longer save new apps, photos, and other data on your iPhone. It also means iOS can no longer delete cache data and other system files to clear up storage on your iPhone.
You can use Google Photos to save space on your device when you delete photos that are safely backed up. Before you use this feature, you must ensure that you've already backed up your photos properly.
Cleaner app for iPhone offers the fastest and easiest way to free up iPhone device storage space by deleting similar photos, screenshots, and large video files. You can also organize your contact list by merging duplicate contacts or deleting incomplete contacts with just a few steps.
On an Android Phone, Go to Settings > Storage
There, you'll see exactly how much space you're using and how much is being devoted to categories such as apps, images, and videos. Tapping on one of those categories provides more detail, such as which apps are using the most space.
When your phone storage is full, it basically means your device is clogged with large files — videos, photos, apps and the like. The culprit could also be memory-hogging junk files…
Mechanical Hard Drives
For most HDDs, it is recommended to leave 15% to 20% of a drive empty. The free space on traditional hard drives is important so that Windows could defragment it. A minimum of 15% free space will allow Windows to properly defragment the drive.
Emails often take up a significant amount of storage space, and it's easy to forget that they're still taking up room in your Trash folder. After you have selected all the emails in the Trash folder, click the Delete Forever button to permanently delete them.
Delete old text messages
You'll be surprised to see how much storage space your text messages take on your smartphone. You may not even realize those messages are being saved to your phone. Don't worry, you can delete them. Be sure to delete messages with photos and videos first — they chew up the most space.
You can free up space in your trash by clearing out deleted emails that haven't been permanently deleted yet. Click on Deleted emails. Important: If you don't have any emails in your trash, you won't be able to open the Deleted emails menu.
If every person only deleted 10 spam emails, they could save 1,725,00 gigabytes of storage space and around 55.2 million kilowatts of power. The average U.S. home uses about 900 kWh per month. More than 61,000 homes could be powered by those same kWh if everyone deleted 10 emails.