I knew this would eventually happen. My tiny little iPhone 5 is so small that its hard drive must be absolutely microscopic. I was waiting for it to run out of space, especially since I don't have any housekeeping utilities to get rid of old unnecessary files.

Okay, I'm joking, but one of my favourite apps, TuneIn Radio, gave me this message:

"TuneIn Radio may require more temporary disk space than is currently available. Try removing files from the device if you experience problems."

So, I guess the question, is: Has my iPhone run out of memory? And what do I do about it?
As far as I know there's no Disk Utility App for the iPhone.

¿Qué?
Since when does an iPhone have a hard drive (other than a plugin/external storage device)?
If there's no "disk", there wouldn't be any "Disk Utility" app.

Nor does an iPhone have a plugin/external storage device.

Remember that iOS is built on the same Darwin kernel as its siblings MacOS, TVOS, and WatchOS uses virtual memory swapfiles, cache files, etc. The temporary disk space Tunein Radio is referring to is Storage space on the solid state drive in your iPhone.

WHERE IS THE STORAGE BEING USED?

While there is no Finder function per. se. there are at least a few ways of finding out how the storage on you iPhone is being used.

1. Settings > General > Storage & iCloud Usage > Storage > Manage Storage will show how much storage is being used by each App and its associated data ranked from the biggest user to the smallest. Touching the App in this display will show a breakdown of how the storage is allocated within the App. While this does not show individual files it will give you an idea of where to start freeing up some storage.
2. Connect your IPhone to iTunes on a computer via USB > click on the iPhone icon > select Summary under Settings will give you a graphic illustration of how the storage is allocated between Music, Movies, TV Shows, Boks, Audiobooks, and Tones (ringtones). Additionally by selecting each of those categories you can see the individual files for each of those categories and you can manage them there.
3. iPhone Apps Within each app on the iPhone you will find the individual data files used by that app.

HOW TO FREE UP STORAGE

Now that you know where your storage is being used you know where to start freeing it up. There are two possibilities delete and move to iCloud.

• PHOTOS Settings > Photos & Camera —
  • turn on iCloud Photo Library
  • turn on Optimize iPhone Storage
  • turn off keep normal photo in portrait and HDR modes
• MUSIC Settings > Music
  • turn on iCloud Music Library
  • Turn on Optimize Storage
• Take a hard look at your Apps including games an delete any that you are not using, you can always download the from the App Store at no charge if you decide to take them up again.

These changes will take a while to "settle" and you may have to invest 99¢ a month for additional iCloud disk space but if your storage usage is normal that should free up enough storage.

Apple would contend that they do have an external storage device. It is called "iCloud" and it works very well if you choose to use it.

Tell them that at MacWorld: 18 best external storage devices for iPhone & iPad

You might want to send a letter to the editor ...

Restated to reflect original context: Nor does an iPhone have a plugin/external storage device with a hard drive.

Thanks for the link.

Note: Applicable to joemike's comment, too.

Okay, I found the Storage Usage settings, and went through all of the items.

I guess I had far more photos than I thought. Deleted most of them because they were mostly junk.

Found a few apps that were not very large by themselves but for some reason had accumulated a lot of storage. I deleted these too.

Even after all of this, it shows 11.56 GB used and only 1.24 GB free. I don't have very many apps on the phone, so I assume this is mostly used by iOS. Does this sound reasonable?

Also, there are a bunch of photos that I can't delete for some reason. These are photos that were not taken with the built-in camera, but were downloaded from my Mac one time when it was synched. Any idea how to delete these?

I started Delete photos...iPhone 4 with precisely the same question, albeit regarding a different model phone.

Doing it via the cloud as per joemikeb or completely wiping the phone are apparently my only solutions.

I think I managed to delete the synced photos. I just went back to the sync folder on the Mac and deleted them from there, then re-synced the iPhone. After that, they were gone.

I also realized that there was a bunch of music on the phone that I didn't want, so I changed the sync settings so that it deleted those.

OK, so color me lazy...if not worse!

As I mentioned, I thought (read ASSumed) that if I emptied the folder and re-synced I'd still have an empty folder on my iPhone, so I never bothered to try, but I've now followed your lead, and the folder is gone along with the pics.

Many thanks for the push.

(Since I wanted to retain the pics in question on my deuced Mac(hina) I had to move them out of their home folder, sync, and then move them back...a more cumbersome procedure than I tend to expect from Apple.

I still feel that there ought to be a means to delete synced material from my (any?) iPhone expeditiously!)

It seems that if it's something that iTunes put onto the iPhone, then only iTunes can get rid of it.

This is the thing that's always irritated me about iOS. There's no user accessible file manager. On Android, you can see your files and delete them.

In iOS files are app-centric, in other words they are part and parcel of the app itself. This is extreme sandboxing for the sake of security. Even iCloud file access to or from iOS is subject to severe strictures imposed by Apple. There have been complaints from some developers that it is too difficult to code their apps to meet the iCloud access standards and use other, arguably less secure, cloud based storage options such as Drop Box. There have been even stronger grumbling from government agencies all over the world because they cannot break into iOS data files. If they can't break in then neither can the bad guys.

For the sake of data security I can easily live without Finder and file access on my iOS devices.

That sounds about "normal". On my iPhone with 16 GB, about 4 GB is consumed by the iOS and related stuff. Hence, a total of about 12 GB for user consumption.

My biggest offender at 800+ MB is Photos and I only have 236 photos on the iPhone. Of that about 12% is Photostream, Apple's "automatic" cloud saver. Photos can be deleted from Photostream, however.

What I am noticing is that apps that used to be "small" are now just large; 100+ MB. These are apps you would think only need to provide access to a server (e.g., banking) but still seem to be large. I think new model iPhones now start at 32 GB for this and other reasons.

But Bob has suggested that MOST of 11.56 GB is used by iOS on his phone...definitely neither "normal" nor even "reasonable".

A few years ago when I was about to start my new job, I went out to buy a new iPhone. I wanted a 5S, 32gb. To my amazement, they didn't have any, the local Verizon only carried 16gb iPhones. (no Apple Stores here) I discussed this with the sales rep, and they explained that "No one wants the 32, they all want the 16. We can special order one for you though but it'll be a few days to get in." So while I stood there in a bit of shock, knowing my 16gb iPod was about full, the other rep walks up to the counter and asks, "do you mind space grey?" NO! I don't mind at all, do you have one? So he reaches under the counter and pulls out one. It seems that someone had special ordered it, and changed their mind and got a 16 instead, so they had this 32 sitting around that nobody wanted.

So I walked out with what *I* wanted. In the end I was sorely disappointed by "Sure you'll get coverage at your new job!". I should have known better, they'll always say that to get a sale. Less than a year later I had switched to US Cellular, where I could actually USE my phone indoors on campus.

I'm still amazed that no one was interested in a 32 even back then. I haven't added much since though.
used: 14.13gb
available: 13.63gb

BE SURE YOU ARE COMPARING APPLES TO APPLES

Figuring out storage usage on iOS devices is complicated by the fact that when looking at Storage and storage allocation in Settings > General > About and other sources on the iOS device itself storage is reported in MiB and GiB where Ki = 1,024, but if you look at the same data in iTunes on your Mac or PC it reports in MB and GB where K=1,000 in other words binary v. decimal. For example in Settings > General > About on my iPhone 7 Plus it reports 231.48 GB (more accurately GiB) of available storage while iTunes reports 248.55 GB. Do the math and 231.48 GiB = 248.55 GB. (NOTE; FWIW both iOS and MacOS actually allocate memory and storage using MiB and GiB internally but Apple used to report memory and storage in MiB and GiB but because of a marketing decision several years ago elected to use the arguably less precise MB and GB. I have no idea why they are inconsistent between MacOS and iOS.)

This is a long discussion to explain why when looking at memory and storage numbers in iOS and MacOS it is important to be certain whether the numbers are base 10 or base 2 (binary).

ACTUAL CAPACITY

I am using my iPhone as an example because I have actual data. It is marketed as having a 256 GB storage capacity. Because that is a Marketing nimble I believe it is safe to assume (I know assumptions are risky) that is a decimal (base 10) value and as far as the actual storage allocation goes it is actually 238.42 GiB. The available storage is 231.48 GiB (248.55 GB) which leaves 6.94 GiB (7.45 GB) unaccounted for. My assumption (again I realize the risk of assuming) is that 6.94 GiB is iOS which is completely consistent with what I find on my 64 GB (59.6 GiB) 12" iPad Pro running the same beta version of iOS.

So as Ira said the size of your OS seems to be in the ballpark.

MY WISH LIST: I understand the lack of a Finder function for iOS but I have a few wishes for storage management:

• Consistent use of GiB or GB between iTunes and Settings (preferably a user selectable option even though only geeks like me would likely know or care)
• It took way too long and I had to go to far too many places to ferret out the information I reported about storage usage on my iPhone. A single point collection place for all the storage data stored several places in Settings, Tunes, Photos, [b]etc[/I] would be well worthwhile. It doesn't have to offer the ability to delete just present an accurate picture of what is stored and the details. I am surprised there isn't a third party app for this, but the task is more complex than I envision or Apple could be resistant for security reasons(?).
• Consistent use of GiB or GB between iTunes and Settings (I know I already said this, but it bears repeating.

I share your amazement and I am equally amazed you get by with only 16GB. I have a lot of friends who have been forced to upgrade because they ran out of storage on their 32 GB iPhones. I went from 32 up to 265 GB on my new iPhone 7 Plus, but that is because I will be taking a lot of HDR photos in TIFF or RAW format as well as some HD videos and too often there is no WiFi or even cellular data connection to upload them to iCloud leaving only the optimized image on my iPhone.

There are still major discrepancies between your (assumed) 7 GiB iOS installation, Ira's (assumed) 4, and Bob's (assumed) 12.

To what might you attribute that?

While browsing through the App Store I came across Cleaner which may provide at least some of the utility you were looking for. I haven't tried it but there is a free version and the Pro version only costs $3. Also check File Manager (FREE)

That is correct. In fact, since my last post, the Free memory has now dropped to 643.3MB and the Used memory is up to 12.16GB, with no new apps installed.

It seems that after deleting a bunch of things, much of the memory didn't really get freed up. I deleted all of my email messages, and the memory usage of the Mail app never changed.

I'll have a look at the Cleaner and File Manager apps and see what they can do. Though, I have a feeling that the simplest fix will be to reset back to factory settings. I don't have anything on the phone that hasn't been backed up anyway.

Assuming your email messages are in an IMAP account, they are stored on the iMAP server, not on your iPhone. Deleting them probably resulted in a marginally noticeable improvement in speed when opening Mail but normally would have negligible effect in the Storage use on your iPhone. The growth in Storage usage might be the result of more and larger Swap files, cache files, and other temporary files. Those temporary files are a function of the number of apps that are open at the same time and what specific apps those are, NOT the total number of apps installed on your iPhone. Deleting apps can free up some Storage but most apps are pretty small.

Before performing a full reset there are two lesser steps that might help clean out your Storage.

1. Restart your iPhone —
   1. Press and hold the Sleep/Wake buttoh on the side or top of your iPhone (depending on the model) until the "Slide to Power Off" slider appears
   2. Swipe the slider to the right to power off your iPhone
   3. When the iPhone has completely powered down Press and hold the Sleep/Wake button until the Apple logo appears on the screen
2. Reset your iPhone —
   1. iPhone 7 and 7+ Press and hold the Sleep/Wake button and the Volume Down button until the screen goes blank.
   2. Older iPhones — Press and hold the Sleep/Wake buttonj and the Home Button until the screen goes blank
   3. Wait untill the iPhone restarts itself and enter your passcode
3. If neither of these frees up any memory and since you have good backups then Settings > General > Reset > Erase All Content and Settings

FYI your terminology is confused. Your iPhone has 3MB of Memory (a.k.a. RAM). It has 16GB of Storage (a.k.a. Disk) and your issue is a lack of Storage not Memory. This may seem nit picking but it can lead to misunderstanding.

Normally, IMAP stores messages in both places, on your phone and on the server. If you move (including move to trash, aka 'delete') a message, it moves it locally, and next time it talks with the server, the server also moves it. The local cache of any other computer using the same IMAP account will move it accordingly also when the server informs it of the move.

This allows you to read your email offline. Otherwise it would be like webmail, no connectivity meaning you can't read your mail.

Although, if you make a LOCAL folder on your mail app, and move an email into there, it will be deleted from the IMAP server and not cached anywhere, getting removed off other synced computers as well. So be careful what you move into a "local mail folder", when you do that it exists only on that computer.

I don't know of any way to tell your computer to "not sync this folder" if you have a folder in your IMAP that you don't want cached on your phone.

I have used "on my Mac" folders for years but how do you make a "local mail folder" on an iOS device like the OP is using?

Actually my email is a POP account.

Here is what my iPhone says is the itemized storage consumption for each app:


The total at the bottom is my own addition. However, the iPhone says that total used storage is 12.15 GB, and only 652.6 MB is available. So, something is using an enormous hunk of storage that the phone isn't able to display.

Edit:
Forgot to mention that I did reset the phone when the storage didn't get freed up, but it didn't change anything. So, it looks like I'll have to do a factory reset.

If you're near an Apple Store it would be interesting to hear what they have to say about your problem; they may have a utility that will give them answers that we mere mortals can't get at.

I don't think you can. With the main mail view open, tap Edit in the upper right. That lets you toggle the view of mailboxes and arrange them. At the bottom you can tap "New Mailbox" but you have to select an IMAP account to create it in. That's where I would expect a "LOCAL" option to be.

On the mac, you can select New Mailbox from the menu, and have "On My Mac" as an option. That's for making a local folder.

We don't have an Apple store, but there is an Apple authorized dealer just a few blocks from where I live with a pretty good service department. I may drop in and ask the service guy next time I'm over there.

Meanwhile I found a discussion of the problem on discussions.apple.com. One person said that simply syncing the phone isn't enough to restore the missing storage, and suggested doing a backup followed by a restore. I tried this to no avail. However, I downloaded the free iBackupBot utility which can be used to examine the files in the backup. Interestingly, the total size of the backup files is only about 650MB. So, there's no excess consumption in the backup. So, it looks like the next step will be to do a factory reset followed by a restore from the last backup. I'll let you know what happens.

Success!!!
I did a factory reset and then restored the last backup. I now have 11.33 GB available.

, but too bad you couldn't get to a tech support guy beforehand to find out what was eating your space.

I hope there's not a next time, but it's worth keeping mind if there is.

Yeah. Just too lazy to head over there.
From what I've read, some deleted apps can leave behind detritus that iOS is unable to free up. At least I now know what to do, and it's quite straightforward.

Meanwhile, I'm keeping watch on the available storage to see if it starts disappearing again.