What is the difference between NFC and NFD?

NFC stores each accented Vietnamese letter as a single precomposed code point, while NFD stores a base letter followed by separate combining accent marks. Both display the same when rendered correctly, but they are different byte sequences that compare and search differently.

Why does my Vietnamese text show floating accents?

That usually means the text is in NFD decomposed form and the font or renderer is not stacking the combining marks properly. Converting to NFC merges each letter and accent into one code point, which almost always fixes the display.

Why do the code-point counts differ between forms?

In NFD each accented letter expands into two or three code points, so the total is higher than NFC even though the visible text is identical. Comparing the counts is a quick way to tell which form you have.

Which form should I store data in?

NFC is the safest default for databases, filenames, and web pages, because most software and search engines expect precomposed text. Use NFD only when a specific system, such as some macOS file APIs, requires decomposed form.

Is my text sent to a server?

No. Detection and conversion use your browser's built-in Unicode normalization locally. Nothing you paste is uploaded, so it is safe for private content.

Vietnamese Precomposed vs Decomposed Unicode Normalizer

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This tool diagnoses and fixes Unicode encoding problems in Vietnamese text. Vietnamese diacritics can be stored two ways, and a mismatch causes accents to float over letters, search to miss results, and duplicate-looking strings to compare as unequal.

How it works

The tool normalizes your input both ways and compares it against the original to detect its current form. NFC (precomposed) packs each accented letter into a single code point, such as ế at U+1EBF. NFD (decomposed) stores a plain e followed by combining circumflex and acute marks. By counting code points and combining marks, the tool can tell NFC from NFD from mixed text, then offers both converted forms to copy.

Example and notes

The string Tiếng Việt looks identical in both forms but takes more code points in NFD because each accented vowel splits into a base letter plus marks. If you paste text and the detected form is NFD or mixed, convert it to NFC for storage and display — that is what databases, URLs, and most fonts expect. Reach for NFD only when a specific system demands decomposed input.