Warning: this code has not been maintained for years and has several issues. Most of it might still work, but I recommend you only use this repository for reference.
This browser extension for Firefox/Chrome allows vocabulary.com users to add words from any web page to their vocabulary lists. It also offers translations to any language in the world learning game and links to clarifying services like Google Images or the Urban Dictionary.
Install via your browser's extension store:
Adding words
Select a word or range of words on any website, right click, and you'll be able to:
The surrounding sentence of the world will automatically be picked up, and listed as a source of the word in vocabulary.com. This also works on Firefox for Android, using a pop-up after selection instead of the Android context menu.
Seeing translations
Translations automatically show up in the word learning game and on definition pages. Click the language abbreviation to change language.
Useful side links
The extension automatically adds links to services like Google Images, YouGlish, GIPHY, ... to further understand words. They appear in the word learning game explanations, in words lists and on definition pages.
Examples in the word game
If training a specific list (assignment), the user-created examples of that list will be shown in the explanation.