What is the difference between NFC and NFD?

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Unicode Normalizer (NFC, NFD, NFKC, NFKD)

Convert and compare Unicode strings across all four standard normalization forms: NFC, NFD, NFKC, and NFKD with character count and byte metrics.

INPUT UNICODE TEXT TO NORMALIZE

58 chars • 15 words

Standard Unicode Normalization Forms

W3C & Unicode 16.0 Specification

NFCCanonical Composition (NFC)

Transformed

Characters are combined into composed precomposed forms (e.g., e + ´ = é). Recommended default for web content (W3C standard).

Café résumé — 2⁴ = 16 & ½ cup — ﬃ ligature — é decomposed

57 chars • 72 bytes

NFDCanonical Decomposition (NFD)

Transformed

Characters are separated into base letters followed by combining diacritical marks (e.g., é = e + ´). Used by Apple HFS+ filesystems.

Café résumé — 2⁴ = 16 & ½ cup — ﬃ ligature — é decomposed

61 chars • 76 bytes

NFKCCompatibility Composition (NFKC)

Transformed

Applies compatibility decomposition (normalizing ligatures, fractions, superscripts to standard forms) followed by canonical composition.

Café résumé — 24 = 16 & 1⁄2 cup — ffi ligature — é decomposed

61 chars • 73 bytes

NFKDCompatibility Decomposition (NFKD)

Transformed

Decomposes all characters by both canonical and compatibility mappings (e.g., 2⁴ becomes 24, ½ becomes 1/2, ﬁ becomes fi).

Café résumé — 24 = 16 & 1⁄2 cup — ffi ligature — é decomposed

65 chars • 77 bytes

Which Normalization Form Should I Use?

NFC (Canonical Composition) is the official W3C web recommendation and standard for database storage and indexing. It ensures that accented letters like é are represented as a single compact code point (U+00E9) rather than two separate bytes (e + \u0301).

NFKC / NFKD (Compatibility Forms) are ideal for search engines and natural language processing (NLP) because they map typographical variants (such as fullwidth letters, fractions, superscripts, and ligatures like ﬁ) back to plain ASCII letters (fi).

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Frequently Asked Questions

NFC (Canonical Composition) combines characters and diacritics into precomposed forms (e.g. 'é' as 1 code point U+00E9). NFD (Canonical Decomposition) separates them into base letters and combining marks (e.g. 'e' + combining acute accent U+0301).

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