Problems downloading large zip file from DropBox

February 22, 2019 10:49 AM

I need to download a large (160 GB) zip file from DropBox. It keeps getting corrupted. Is there any way to improve reliability for the download process?

The organization that sent me the link is claiming that the problem is on my end, because other people have successfully downloaded the file. I've tried downloading it twice through Google Chrome. It took about 3 hours each time. In both cases, the zip file seemed to be corrupted. When I would try to run 7-Zip on it, I'd get multiple errors saying, "Unsupported compression method". Using the built-in Windows 7 decompression method didn't work, either. It says that the zip file is invalid.

posted by JD Sockinger to Computers & Internet (8 answers total)

Can you ask the organization providing the file to provide an MD5 or SHA-1 hash for the file? You can then verify that the download is correct by checking that hash against the output of Microsoft's File Checksum Integrity Verifier (installation instructions here).

(A hash or checksum is, among other things, a way to verify that two files are exactly the same by comparing a special fingerprint value calculated from the files. MD5 and SHA-1 are two of the most common methods for doing this.)

This would let you verify that you have successfully downloaded an exact copy of the file.

As an alternative to Chrome, you may also be able to use Microsoft's BITSadmin program that should be included with Windows 7. Here is an example, using a fake Dropbox link:

bitsadmin /transfer myDropboxDownload /download /priority normal https://www.dropbox.com/s/abcdc6trai1x2y3/giant_file.zip?dl=0
posted by jedicus at 11:01 AM on February 22, 2019 [1 favorite]

If you have a crappy WiFi connection, that can be the source of corruption right there. Try plugging you computer directly into the router with an Ethernet cable.
posted by rockindata at 11:35 AM on February 22, 2019

Make sure the disk you're downloading to actually has 160 GB of free space. I can't remember if it was Dropbox, but I ran into this recently when trying to download a very large file from a cloud service. There was no indication I was out of space -- I really thought the file was corrupt until I investigated further.
posted by Mothlight at 11:56 AM on February 22, 2019 [1 favorite]

Response by poster: Thanks for the tips. A few points based on the above:

I can ask, but I think it's unlikely that the organization would provide me with the MD5 or SHA-1. I'm too small a fish for them to bother with.

I wasn't using WiFi. I was using a Windows desktop PC with a wired connection to a fiber optic line.

I definitely had enough space on the hard drive for the file.
posted by JD Sockinger at 12:25 PM on February 22, 2019

Best answer: You'll probably have far better luck installing the Dropbox client on your computer, and then adding the file to your own dropbox so it syncs to your computer (there should be a link to do so on the file's download page). The client will ensure that the file is downloaded in its entirely and that its contents match what is stored on Dropbox's servers. Downloading a file in a web browser offers no such assurance unless you do the MD5 or SHA-1 validation step yourself after you download it.
posted by zsazsa at 12:27 PM on February 22, 2019 [5 favorites]

Yes, generally in my dropbox experience, “sharing” the actual file/folder is more reliable than just a download link.
posted by jeweled accumulation at 6:34 PM on February 22, 2019

The other benefit of syncing to dropbox is that a file can be partially synced and then resumed later, whereas browser downloads will be totally cancelled if you interrupt them.
posted by ahundredjarsofsky at 10:25 PM on February 22, 2019

Response by poster: I had high hopes for zsazsa's approach. I installed the client and synced the file. No dice -- it still doesn't work. I don't know what's going on. Maybe the source file is corrupt, despite the assurances of the sender.

Anyway, I gave up on trying to download it, and I convinced the sender to overnight a USB drive to me, instead (which they did).

Thanks go out to everyone for your tips.
posted by JD Sockinger at 7:01 PM on March 3, 2019 [2 favorites]