Google Translate does not offer Norwegian Nynorsk. This translator asks Google for Norwegian (Bokmål), the closest language it does offer, and then rewrites that into Norwegian Nynorsk with a documented set of rules: word swaps, sound changes and grammar. It is a rule-based rewrite, not a human translation, so check anything that matters with a speaker.
73.2 on 300 real sentences; Google's Norwegian (Bokmål) as is: 57.2.
The score is chrF: how closely the output matches what real Norwegian Nynorsk speakers wrote, character by character, from 0 to 100. Tested on 300 Nynorsk sentences from Tatoeba with their English, held out and never read: the English goes through Google into Bokmål, then the mod; the rules were learned from 10,109 other sentences.
Norwegian Bokmål rewritten into Nynorsk by rules: the Nynorsk forms of the common words (eg, ikkje, ho, kva, dei, vere, berre, mykje, nokon), the spellings that reach words nobody listed (kv- for hv-, -leg for -lig, -heit for -het), learned from thousands of Nynorsk sentences. No output is written by an LLM.
The rules are a plain file anyone can read, test and copy. Every translation shows Google's Norwegian (Bokmål) underneath, so you can see exactly what the rules changed.
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