Overview
PeekCopy is a Chrome extension. PeekCopy copies words you 'peek' at in DuoLingo translation challenges and makes them (and their translations) available to you in a format that is easy to import into a flash card application (e.g. Anki).
Usage
You can install PeekCopy via the Chrome web store here or by downloading the files from this repository and installing as detailed here.
Once installed, use DuoLingo like normal! As you go through the skill tree for your preferred language, encountering a translation challenge and hovering over a word to see potential translations will cause PeekCopy to copy that word to your wordlist. You can access your wordlist at any time by clicking on the PeekCopy icon in your address bar, which should be visible any time you're on DuoLingo.