Acknowledgements

• FlorisBoard

  Duoboard’s swipe classifier is a modified Swift port of FlorisBoard’s statistical glide typing classifier. Copyright © 2025 The FlorisBoard Contributors. Licensed under the Apache License 2.0.

• wordfreq

  The word list ranks words by wordfreq’s English frequencies, by Robyn Speer, which draw on Google Books Ngrams, SUBTLEX, OpenSubtitles, Wikipedia, NewsCrawl, GlobalVoices, Reddit, Twitter and OSCAR. Licensed under CC BY-SA 4.0. github.com/rspeer/wordfreq.

• Wiktionary

  Which words exist and how they’re capitalized come from English Wiktionary, via kaikki.org’s extract made with wiktextract by Tatu Ylonen. Licensed under CC BY-SA 4.0.

• Wikipedia

  Names and their spellings come from English Wikipedia article titles, ranked by Wikimedia clickstream data (CC0). Which words follow which comes partly from English Wikipedia text. Wikipedia content is licensed under CC BY-SA 4.0.

• Tatoeba

  Which words follow which also comes from Tatoeba’s English sentences, licensed under CC BY 2.0 FR. tatoeba.org.

• Unicode and emojilib

  Emoji names and keywords come from Unicode’s emoji data and CLDR annotations, Copyright © 1991–2026 Unicode, Inc., under the Unicode License v3, with extra keywords from emojilib, Copyright © 2014 Mu-An Chiou, MIT License.

• SymSpell

  Duoboard 1.0’s word list was built from SymSpell’s English frequency dictionary. Copyright © 2018 Wolf Garbe. MIT License.

• Google Books Ngram

  SymSpell’s word frequencies came from Google Books Ngram data, licensed under CC BY 3.0. Duoboard filtered, truncated and re-ranked them.

• SCOWL

  Spellings and capitals are checked against SCOWL’s en_US and en_GB dictionaries. Copyright 2000–2026 by Kevin Atkinson, used under its permission notice, which includes the UKACD notice and data Copyright 2016 by Benjamin Titze. github.com/en-wl/wordlist.

The Duoboard app lists these under Settings → Acknowledgements, with the Apache License in full.