Not necessary. In a computer you only (if you feel like it) defrag a hard disk. A lot of modern computers, especially the more expensive laptops, and all tablets and phones don't have a hard disk (but an SSD, or other electronic memory) and there's no need to defrag those media.
Kees
I am constantly deleting old unwanted photos and apps does this leave gaps on my phone, like on computers? If this the case how would we get our older phone run like new?

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