- 2017-06-15 - No longer works on Pale Moon 27.0.1 (x86)
2015-06-12 - Tested and works on Pale Moon 25.5.0 using British English Dictionary (Forked by Marco Pinto) 2.25
The addon to install ∞
Modifying about:config ∞
TL;DR: about:config - spellchecker.dictionary.override;en_GB
Specifying another dictionary is the same, replacing "en_GB" with your language code. Consult your dictionary or dictionary addon for help with its language code.
Setting Pale Moon to use it ∞
Bugs (in Firefox) ∞
2015-06-12 - This is bugged. I can alt-tab out and back, and the language is switched back to American English.
- Bug 1073827 - Spellchecker fails to honour/remember user's choice of language/dictionary
Bug 1073840 - Pref: Always honour setting of spellchecker anguage/dictionary in user prefs, regardless of lang attribute or Content-Language header