What a file checksum can—and cannot—tell you
A checksum is a fingerprint of bytes, useful for detecting a changed or incomplete download.
One changed byte changes the result
Hash the downloaded file with the same algorithm used by its publisher. A matching SHA-256 value means the files agree to an extremely high level of confidence.
Trust the place you get the expected hash
If a malicious actor replaces both a file and its published checksum, the two will still match. A hash by itself does not establish who created a file or whether it is safe.
Local processing keeps the contents on your device
The checksum tool reads the file in your browser. It does not send your file to a server. Keep in mind that downloaded libraries and normal page requests are separate from the content you select.