What this tool does
NYSIIS — the New York State Identification and Intelligence System phonetic algorithm — was published by Robert Taft in 1970 to match names in criminal-justice databases. It is reported to be about 2.7% more accurate than Soundex for name matching because it transcodes whole letter groups and keeps more of a name’s structure. This encoder produces both the classic 6-character key and the full key in your browser.
How it works
NYSIIS runs in stages. First it transcodes leading and trailing clusters:
leading: MAC -> MCC KN -> N K -> C PH/PF -> FF SCH -> SSS
trailing: EE/IE -> Y DT/RT/RD/NT/ND -> DThe first letter of the transformed name becomes the start of the key. The encoder then steps through the remaining letters, applying transcoding rules: vowels become A, EV becomes AF, Q becomes G, Z becomes S, M becomes N, KN becomes N, SCH becomes SSS, PH becomes FF, and H or W are replaced by the previous letter in certain contexts. Throughout, a new character is appended only if it differs from the last character already in the key, so consecutive duplicates collapse. Finally a trailing S is removed, a trailing AY becomes Y, and a trailing A is dropped.
Example and notes
“MacDonald” encodes to a key beginning MCDANALD (6-char key MCDANA), “Watkins” to WATCAN, “Jackson” to JACSAN and “Knight” to NAGT. The classic key is truncated to six characters for fixed-width indexing, while the full key helps when you want a tighter comparison. Like all phonetic codes, a shared NYSIIS key means two names are good candidates for being the same — confirm matches with additional fields or edit distance before merging records. Everything is computed locally.