If you are unable to delete certain photos on iPhone, it is likely that the photos that you are trying to delete are not actually located on the internal storage location of your iPhone.
This happens, when iCloud photos are enabled on iPhone, which results in photos from other devices showing up in the Photos App. Since, iCloud photos exist on iCloud servers and not on the internal storage location of your iPhone, they cannot be deleted or removed from your device.
Similarly, photos manually transferred to iPhone from Mac or Windows computer cannot be deleted on iPhone, as they do not have a delete button or delete option associated with them.
Can’t Delete Photos on iPhone
While individual iCloud photos cannot be deleted on iPhone, you can easily get rid of all the iCloud photos from iPhone by disabling iCloud Photos on your device.
However, disabling iCloud photos does not remove photos that were synced or transferred to iPhone from Mac via Finder and Windows computer via iTunes.
The only way to remove synced photos from iPhone is by plugging your device to the computer (Mac or PC) from which they were synced and reversing the sync process.
1. Remove iCloud Photos from iPhone
As mentioned above, you can remove all iCloud Photos from your iPhone by disabling iCloud Photos on your device.
1. Open Settings > tap on your Apple ID Name.
2. From Apple ID screen, go to iCloud > Photos > move the slider next to Sync this iPhone to OFF position.
3. On the confirmation pop-up, select Remove from iPhone option to remove all iCloud Photos from your device.
Note: Removed photos will still be available in your iCloud Account and they can be easily downloaded to your Mac or Windows computer.
2. Remove Synced Photos from iPhone
After disabling iCloud photos, you may still find certain photos on your iPhone which cannot be deleted, due to the “Delete” or “Trash” option being greyed out.
As you must have guesses it, these undeleteable photos have been synced or transferred to your device from Mac using Finder and Windows computer using iTunes.
The only way to remove Synced photos from iPhone is by connecting your device to the same Mac or PC from which the photos originally came from.
2.1. Remove Photos Synced from Mac on iPhone
If you are using a Mac, follow the steps below to remove Photos Synced from your Mac to iPhone.
1. Plug iPhone to the Mac from which the photos originated.
2. Open the Finder on your Mac.
3. Select your iPhone in the left pane. In the right pane, switch to Photos (1) tab > check Selected Albums (2) and Uncheck Photo Albums (3) that you want to remove from iPhone.
4. Once you are done Unchecking Photo Albums, click on the Apply button.
5. Wait for above changes to Sync back to your iPhone.
Once the syncing process is completed, all Photos that came to your device from Mac will be removed.
2.2. Remove Photos Synced from Windows PC on iPhone
In the case of Windows computer, the interface is a bit different, but the steps are practically the same.
1. Plug iPhone to Windows Computer.
2. Open iTunes and click on the Phone icon as it appears in iTunes.
3. Next, select Photos (1) in the left-pane. In the right-pane, check Selected folders (2) and Uncheck Photo Albums (3) that you want to remove from iPhone.
4. Once you are done Unchecking Photo Albums, click on the Apply button.
5. Wait for above changes to Sync back to your iPhone.
Once the Syncing Process is completed, all Photos that were Synced from Windows PC on your device will be removed.
Which Photos Can Be Deleted on iPhone?
Photos & Selfies that you take using the rear and front camera of iPhone are are stored on the local storage of your device and they can easily deleted from iPhone.
Photos received via AirDrop and downloaded to iPhone from iMessages, WhatsApp, Email Messages and other Apps can be deleted, as they are also stored and managed by the local storage system of your device.
While photos synced (transferred) from Mac (via Finder) and Windows PC (via iTunes) are also stored on the local storage of device, they cannot be deleted from iPhone due to lack of “Delete” or “Trash” option.
You can find these photos in Albums with “From My Mac” or similar titles, indicating that the storage and handling process of these photos is managed by the computer and not iPhone.