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I bought a Mac recently and I am very new to Mac. The seller says its 512 GB but from the screenshots below I don't know if its 512 GB or 256 GB please kindly let me know.

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    Jul 28 at 23:37

2 Answers 2

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That system has 256 GB of storage.

According to both of those screenshots you do not have 512 GB storage on that Mac. There is only 256 GB of storage.

The easiest way to see this is via the “About This Mac > Storage” tab screenshot you have posted.

“About This Mac > Storage”

The two areas you can see it is in the text beneath the storage icon that reads “251 GB Flash Storage” as well as the calculation graph with the text that reads “224.71 GB available of 245.11 GB.”

And, if you care, the difference between 251 GB and 245.11 GB can be explained by the spaced taken up the recovery partition as well as Time Machine snapshots. So 245.11 GG is normal for a 256 GB storage device like this. But it sure as hell isn’t 512 GB storage as the seller claimed it is!

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If your seller has just run df to check the size and naively taken the largest figure, then that's maybe why they reckoned it was 512GB. That's really giving the benefit of the doubt to the seller though, given that there are other ways to demonstrate a disk's size, as you have done yourself.

On macOS df without any modifying flags counts in 512 byte blocks, not 1k blocks like Linux systems by default.

eg. On my 1TB system:

% df
Filesystem                              512-blocks       Used Available Capacity    iused      ifree %iused  Mounted on
/dev/disk3s1s1                          1942700360   30113968 925234592     4%     502047 4293722350    0%   /
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1942700360 could be lazily rounded up to 2TB without checking the units of measure. Whereas df -k (or even df -g for GB) gives a slightly less prone to error figure:

% df -k                                                                
Filesystem                              1024-blocks       Used Available Capacity    iused      ifree %iused  Mounted on
/dev/disk3s1s1                            971350180   15056984 462583944     4%     502047 4293722350    0%   /

Your screenshots indicate disk0 (the actual physical disk) to be 256GB. All the other diskutil lines indicate the sub-partitioning.

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