What does NFKC normalisation do?

NFKC stands for Normalization Form KC, or Compatibility Composition. It applies compatibility decomposition, which folds variants like ligatures and full-width letters into their plain forms, then recomposes combining marks into precomposed characters.

How is NFKC different from NFC?

NFC only handles canonically equivalent sequences and preserves the original characters. NFKC additionally collapses compatibility variants, so the ligature fi becomes the two letters f and i, and the full-width A becomes a normal A. NFKC can therefore change which characters appear.

When should I use NFKC?

Use NFKC for identifiers, usernames, search keys, and security checks where you want visually distinct but compatible forms to be treated the same. It prevents tricks like full-width or styled characters bypassing a filter.

It can be. Folding a superscript two into a normal digit two loses the superscript styling, and that cannot be reversed. Use NFKC for comparison and matching, not for round-tripping formatted text you need to preserve.

Does the tool send my text anywhere?

No. NFKC is applied with the browser's built-in String.prototype.normalize, so all processing is local and nothing is uploaded.

Unicode NFKC Normaliser

NFKC (Normalization Form KC) goes beyond canonical equivalence and folds compatibility variants such as ligatures, full-width letters, superscripts, and circled characters into their plain equivalents, then composes any combining marks. It is the form to use when you want visually styled look-alikes to be treated as the same text. This tool applies NFKC and shows the code points before and after.

How it works

NFKC is a compatibility decomposition followed by a canonical composition:

1. Compatibility Decompose  ﬁ -> f i      Ａ -> A      ² -> 2
2. Canonical Compose         recombine base letters + combining marks

The compatibility step replaces characters that are not identical but are considered equivalent for many purposes, then composition tightens the result back into precomposed characters where possible. Processing uses the engine’s native String.prototype.normalize("NFKC").

Notes and example

Folding the ligature ﬁ produces the two letters f and i, the full-width Ａ becomes A, and the superscript ² becomes 2. Because this discards styling it is not reversible, so reserve NFKC for matching, deduplication, and security checks rather than for storing display text. For the same folding without recomposition, where every combining mark stays separate, use the NFKD tool.