Running out of disk space / no space left (Windows phone)

If your device supports an microSD card, install one, and preferably the largest one in size that your device will support, Then all your photos will be stored there, keeping the internal memory clean, and at the disposal of the operating system.

If your mobile device supports MicroSD cards, consider moving personal data files to it (photos, videos, music). Too much photos, videos, music can decrease your device's performance once it runs out of memory. The operating system needs free space in order to work properly.

To move personal data files to a MicroSD card:

Storage sense -> Phone -> select a category of files you want to manage (e.g. pictures, videos, sounds) and tap on it -> Select the file you want to move (or tap on the select button   if you want to move more files than one) -> tap on "..." -> Save to SD card

Note:
Windows phone OS (8 and higher) allows you to save file directly to the MicroSD card:

Open Storage Sense from the apps list -> Store new apps on -> Change it to SD Card

Also, you can download the official Windows Phone file manager called Files from the Windows store, and manage the files through it.

Note 2: Not every file can be moved to the MicroSD card, because there are files which are system protected

Too much applications installed in your device's internal memory may slow it down, since the operating system requires free memory in order to function properly. If your device supports a MicroSD card, move the applications to it.

To move applications to MicroSD card:

Tap on Storage Sense from the Apps list (swipe to the left to access the list) -> Phone -> Apps + games -> Tap the application you want to move (or tap the select button to move more than one application -> tap on "..." -> Move to SD

Note: Not every application can be moved to the MicroSD card because there are some system applications which must be in the device's internal memory.

If you have too much photos, music, videos, games and other memory-consuming content stored on your mobile device, it's no wonder why your mobile device is slow.

To speed it up, you need to free up some space. You can improve it by deleting unnecessary personal data files (photos, videos, music, etc.). You can delete them either through the respective viewer applications (picture, music, video), or from Storage Sense:

From the Apps list (swipe to the left) open Storage Sense -> Phone -> Select a category of files (photos, videos, sounds) -> Manage -> Tap the select icon   -> Select photo(s) -> Tap on Delete (the recycle-bin icon)

Too much text messages can slow down your device because they occupy your its memory. To delete messages:

Go to Messaging from the Apps list (swipe to the left)-> tap and hold the message or thread you want to delete (or tap to the left of the message or thread, if you want to delete more messages)-> Delete

Note: Deleting threads with only text-based messages won’t free up much space on your device, so, concentrate on messages that include a lot of images, videos and voice notes.