Filesize difference?

When I download things in any browser (Firefox, Chrome, Safari) the filesize in the download window doesn't match the size of the downloaded file. A good example is XCode I downloaded recently shows up as 3.42GB in the Safari download window, but when I do a right-click "get info" the file shows 3.78GB...

The XCode .dmg verifies and mounts just fine. This filesize difference happens with files of all size, not just large files. For instance downloading the Firefox 4 Beta shows 27.3MB in the safari download window, and the "get info" shows 28.6MB. Any ideas as to why this happens?

The filesize of XCode shows up as 3.42GB on the apple developer site as well. It's almost as if my downloads are getting bloated somehow... at least that is what it seems like. But .dmg's verify and mount, so that means that the file is not corrupted, correct? I was under the impression that if a .dmg verifies and mounts, it is not corrupt.

I suspect it's the old problem of definitions. A Gigabyte is either 1000*1000*1000 bytes or 1024*1024*1024 bytes. The smaller way is 1,000,000,000 bytes, the larger is 1,073,741,824 bytes, or 7.4% larger. The difference on your two file sizes is about 11 %, so most if that is probably the definition. The rest could have something to do with sectoring, which depends on the drive size. In any event. don't worry about it, it's not a puzzle worth sweating over.

Jakerich has it, for the most part, right. The size of the file reported during the download is that which is being reported by the server - in Base 2 - like everyone and everything except the hard drive manufacturers which use Base 10 for advertising the size of their drives.

Apple, with Snow Leopard, introduced the first OS to use Base 10 related to what the end user sees. So, after the file is downloaded, you're seeing a file size reported in Base 10 vs Base 2.

I think Apple, like the rest of us geeks, got tired of explaining the answer to this question to a large percentage of folks calling up tech support.

We probably got 2-3 questions a week here in this forum asking, "I just bought a 1TB drive, and now I have it installed but it only has 930 GB- why?". And the inevitable, "Apple, WD, Seagate, et al; is ripping me off" line due to no comprehension of a matter that has been with us as long as we've been able to purchase computers and hard drives.

These questions have now all but disappeared on this forum since Snow Leopad came out. While our Windows forum cousins are still having to deal with the same age old question on an almost daily basis... and sorry, but it gets old and tiring.

Hi jakerich and bobtomayan, can you guys confirm that this happens with your downloads too? Btw, thank you guys so much for taking time to help. I never even thought about definitions but that does make sense. I thought my files were being corrupted somehow...