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Unicode Normalization Collision Checker

Find distinct identifiers that collapse to the same value under NFC, NFD, NFKC, or NFKD without uploading them.

Treat each line as a filename, ID, or key. This exposes decomposed characters and compatibility forms that may collide in storage or search systems.

The check runs only in this browser. Your identifiers are neither uploaded nor stored.

Identifiers to compare (one per line)

Empty lines are ignored. The limit is 100,000 lines and 1,000,000 UTF-16 code units.

Normalization form

Diagnostic result

Enter identifiers to run the check.

How to use

  1. 1

    List identifiers

    Paste filenames, user IDs, or database keys with one value per line.

  2. 2

    Choose a form

    Start with NFC. Use NFKC or NFKD only when compatibility characters are relevant.

  3. 3

    Review the originals

    Compare source lines and code points, then decide which spelling is authoritative.

Scope of the result

The checker does not reproduce operating-system, database, or locale-specific collation. It reports only collisions produced by Unicode normalization.

Frequently asked questions

Should I use NFC or NFD?
Follow the contract of the destination system. This tool does not choose a standard; it shows which originals collide under the selected form.
Can I replace everything with NFKC?
That is not recommended. Compatibility normalization can change the meaning of units, symbols, and presentation characters.
Are my identifiers uploaded?
No. Normalization and grouping happen only in your browser.