Data Transfers · Downloads and large files
How do I know a large download finished correctly and isn't corrupted?
Short answer: Each piece is checked as it arrives and the finished file is checked again; the log says “…is complete and verified”. If the assembled file is wrong it isn't kept and nothing at the destination is overwritten.
Large downloads are checked before they're marked finished. Each piece is checked as it arrives, a piece that didn't arrive intact is fetched again, and when everything is put together the result is checked again. The log ends with "…is complete and verified" when all is well.
If the assembled file isn't right — for example "The assembled file came out the wrong size, so it wasn't kept" — the faulty file isn't kept and nothing at the destination is overwritten.
If the website publishes its own checksum for the file, you can also compare that yourself for extra peace of mind.
Related: Large downloads that resume