Whether the files are identical, the offset of the first difference, and the total differing bytes.

Are my files uploaded?

No, both files are compared entirely in your browser.

Can it compare different-sized files?

Yes — the size difference is counted toward the differing bytes.

Drop two files to compare them at the byte level: identical?, first differing offset, and how many bytes differ. All local.

ADrop file AProcessed in your browser — never uploaded.

BDrop file BProcessed in your browser — never uploaded.

Drop a file into both A and B to compare.