10ten Japanese Reader (Rikaichamp)

Quickly look up Japanese words on any text page by activating the add-on from the toolbar (you may need to use the Extensions menu to pin the icon to the toolbar) or pressing Alt+R.

Features: • Pitch accent information • Dictionaries that update automatically twice a week • Recognition of a wide range of grammatical forms and characters (e.g. 食べてた, 分からん, 知らん, じーちゃん, 頑張ろー, そーゆー, ぬ verbs, とく・どく forms, causative passive, vs-c verbs like 兼した, and characters like ㋕, ㌀, ㋿, 𠏹沢, and many more) • Translation of Japanese numbers into Arabic numerals (e.g. 13億5千万 into 1,350,000,000) • Translation of yen amounts (e.g. 100億円, 8万8千円) into a local currency • Translation of Japanese-era years into Gregorian years (e.g. 昭和５６年, 平成三十一年) • Translation between 畳/帖 measurements and square meters (e.g. 四畳半、12.6 帖、25 平米 etc.) • Translation of shogi moves (e.g. ☗８三銀引成) • Support for the widest range of Web content (Google docs, YouTube subtitles, vertical text, SVG images, hidden text etc.) • Support for non-English dictionaries (unfortunately no Japanese-Japanese dictionary is freely available yet) • Up-to-date kanji data including educational and kanji kentei levels, reworked kanji components etc. • Many settings to customize to your needs