NeonLingo

NeonLingo is a Chrome and Edge extension that translates words you select while browsing, saves them to an automatic wordbook, and re-highlights them across sites so vocabulary sticks. It supports 30 languages, adds bilingual word swapping on native-language pages, and syncs FSRS flashcards for signed-in users.

NeonLingo is a browser extension for Chrome and Edge that turns ordinary web reading into vocabulary practice. Select a word you do not recognize and the translation appears inline, in any of 30 languages, without opening a second tab or copying text elsewhere. Every lookup is written to a personal wordbook automatically, and the extension then highlights that word whenever it shows up again on other sites, so review happens through repeated contact with real sentences rather than a scheduled drill. The extension works in two directions. On foreign-language pages, Reading mode offers instant translation with automatic saving, capped at 200 words on the free plan and 500 on Premium. On pages in your native language, Bilingual Reading swaps selected words into your target language. The choice is deliberate: words sit roughly one step above your current level, the surrounding sentence stays in the language you already know, and meaning gets inferred from context. NeonLingo frames this around Stephen Krashen's comprehensible input principle, and the product design reflects it rather than just quoting it. Signing in adds FSRS flashcards that sync across devices for learners who want structured review on top of passive exposure. Premium also upgrades translation so the entire sentence is read, which matters for languages where a word changes meaning by position or inflection. The tool suits self-directed learners, exam candidates, developers reading English documentation, and anyone who reads foreign fiction or blogs for pleasure. Its closest rival, Toucan, swaps words into pages but does not retain them; NeonLingo's differentiation is the loop from lookup to wordbook to cross-site highlight. The trade-off is that the method depends on genuine reading volume, so people who rarely browse in a second language will get little from it. Free to start, no credit card required.