duplicate detection

Duplicate Detection

During DAT generation every file is hashed. When two or more files share the same SHA-256 hash but have different file names, they are the same ROM data stored twice. ROM Validator groups them and shows the Duplicate Files Detected window.

What the window shows

Column	Meaning
SHA256 Hash	The hash shared by every file in the group
Filenames	Comma-separated list of the file names in the group

The header shows the total number of duplicate groups. A warning banner reminds you that the files contain identical data under different names.

Why duplicates matter

• The generated DAT file would contain multiple entries with identical hashes and different names, which makes validation ambiguous.
• Duplicate files waste disk space and can hide an incomplete or incorrectly named collection.

What to do

1. Review each group and decide which file name is correct.
2. Delete or move the extra copies in File Explorer.
3. Re-run Start Hashing so the results reflect the cleaned folder.
4. Export the DAT file.

Note

Duplicate detection is based on SHA-256. Files that are similar but not byte-identical are not reported as duplicates.

Related pages

• Generating DAT Files
• Validating ROMs