To my own surprise I have seen a corrupted file in 2022. Only 70 MB, so really tiny compared to many files handled today.

The file had been built in Europe and after installing it to a US system we wondered why it did not work.

Haven't seen anything like that for many years so it took us a while to even consider the option that it could be corrupted.

(No, we did not spend any time to check whether corruption showed any interesting pattern like a single bit flip, a block of zeros or anything like that. Transferring it again just did it.)

The larger the file the more chance it will get corrupted by cosmic rays. Media also physically decays over time.

Error correction and redundancy is essential, which is why I use par2 and dvdisaster on all my archives.

Shouldn't the download client check for corruption before any download complete?