File hash checker
Drop files to see their hashes
Hashed in your browser · the file is never uploaded
Two files with the same hash are the same file. That makes hashing the quickest way to answer questions a filename cannot: did this copy survive the transfer intact, are these two backups actually identical, which of these forty images are duplicates under different names.
How to check file hashes
For finding duplicates, the size column does most of the work first: files of different sizes cannot be identical, so scan for matching sizes and only then compare hashes. Note that a hash reflects the bytes and nothing else: two photographs that look the same but were re-saved by different software will have different hashes, and a file whose name or timestamp changed will have the same one. That is usually what you want, but it surprises people who expect a hash to track the picture rather than the file.
Questions
Drop them all in and look for repeated digests. Files with different sizes can never match, so the size column narrows it quickly.
CRC-32, by a wide margin, and it is adequate for spotting accidental duplicates. Use SHA-256 when you need certainty.
No. The hash covers the contents only. Name, timestamps and folder are not part of it.
With MD5 or SHA-1, deliberately, yes. With SHA-256 it is not something that will happen by accident or by design.
As many as you like. It runs on your device, so the limit is memory and patience.
No. They are read from disk into this page and hashed there.