British English Dictionary V4 For Firefox, Thunderbird, and SeaMonkey A carefully maintained, community-driven resource for accurate British English spelling. 📢 Update As of March 2025, this dictionary fully aligns with modern -ise verb spellings (e.g., “organise”). 🔗 Websites

https://proofingtoolgui.org (Proofing Tool GUI)
https://github.com/marcoagpinto/aoo-mozilla-en-dict (GitHub)
https://linkedin.com/in/marcoagpinto (LinkedIn)
https://marcoagpinto.com (article about Marco)
https://addons.mozilla.org/addon/british-english-dictionary-2 (Firefox add-on)
https://addons.thunderbird.net/addon/british-english-dictionary-2 (Thunderbird add-on)
https://extensions.libreoffice.org/extensions/english-dictionaries (LibreOffice extension)

🌟 Key Features

150 000+ words added since 2013 (updated to V4)
Based primarily on Oxford and Collins dictionaries
Covers both modern and literary vocabulary
Compatible with Commonwealth/European English variants

🔍 Inclusion Rules

Words must appear in at least two authoritative sources (e.g., Oxford + Collins) (except proper nouns)
Archaic terms included only if they do not conflict with modern usage
U.S. spellings are retained when widely adopted in British English (e.g., “movie”) and validated by trusted sources
- Note: The dictionary's U.S. origins explain why many U.S. words are present.

📥 Installation

Firefox/Thunderbird 115+ (ESR): Install directly from Mozilla Add-ons
Legacy Firefox/Thunderbird (v59 or earlier):
- Download the .xpi file from GitHub: https://github.com/marcoagpinto/aoo-mozilla-en-dict
- Drag & drop the downloaded .xpi file into the Extensions/Dictionaries window
Enable via right-click in an editable text area: “Languages” → “English (United Kingdom)”

📚 Full guide: https://proofingtoolgui.org/en_installing.html 🛠 Developer Commitment

15+ years of continuous updates
Personally funded (hosting, Oxford Premium access, domains)
Open-source collaboration on GitHub
Built on the Proofing Tool GUI framework for transparent validation

❓ FAQ Highlights

Why include “movie”? → FAQ #7
How to report issues → FAQ #4
View full changelog → https://proofingtoolgui.org/en_GB_CHANGES.txt

🤝 Community-Driven This project advances thanks to your input: - Found a missing Oxford/Collins word? → Submit via e-mail or GitHub - Found a U.S. spelling that should be removed? → Provide dictionary citations - Having technical issues? → Report via e-mail or GitHub ℹ Ethical Notes

No AI or automated scraping – all entries are manually verified
Archaic terms included cautiously for literary users
Hosting costs covered privately

This dictionary serves students, professionals, writers, and non-native speakers alike. Your feedback helps ensure it remains the most reliable free British English resource available.