Credits & attributions

Last updated: 13 June 2026

Wrenhouse is built on open frameworks, public datasets, and third-party services. We're grateful to the people and projects below, and we credit them here as their licenses ask.

Language data & frameworks

• CEFR — the Common European Framework of Reference for Languages, by the Council of Europe. Used as the levelling framework throughout the Service.
• CEFR-J Wordlist — © Tono Laboratory, Tokyo University of Foreign Studies, via the Open Language Profiles project. Used (with citation, as its terms permit) to grade vocabulary by level.
• Octanove Vocabulary Profile (C1–C2) — by Octanove Labs, via Open Language Profiles, licensed under CC BY-SA 4.0. Used alongside the CEFR-J data for higher-level vocabulary grading.
• English Grammar Profile — a public CEFR grammar inventory. Our grammar focuses are informed by public CEFR references; they are our own labels, not a reproduction of any proprietary syllabus.

Technology

• ElevenLabs — speech (narration), music, sound effects, and transcription.
• Google Gemini, accessed via the Lovable AI gateway — text and image generation.
• Word definitions via dictionaryapi.dev (data derived from Wiktionary, licensed under CC BY-SA).
• Typefaces — Instrument Serif, Source Serif 4, Inter, and JetBrains Mono, under the SIL Open Font License 1.1.

Trademarks & affiliation

Names such as Cambridge English, IELTS, TOEFL, Oxford, and BEC, where they appear, are the trademarks of their respective owners and are used descriptively only. Wrenhouse is independent and is not affiliated with, endorsed by, or sponsored by any of these organisations. Practice material generated by the Service is for learning and is not an official exam product.

Questions or corrections

If you maintain one of these resources and would like a credit changed, or you spot anything we've missed, email loudproudenglish@gmail.com. See also our Terms.