Sparkle

Sparkle replaces a small number of English words on the pages you already read with the Chinese you are studying. You keep reading; the vocabulary comes to you.

How it works

• Pick an HSK level (HSK 3.0, the 2021 standard). Everything below it is treated as known.
• Words from the next level up are added a few at a time, at a pace you set.
• They turn up in your ordinary reading, and you can drill any of them as flashcards.
• Hover a word — or double-tap it on Android — for the reading, the meaning, and the English it replaced.

Everything happens on your device, and the add-on contains no code that could send anything anywhere. There is no account, no sign-in and no analytics. The dictionary ships inside the add-on and the substitution is worked out in the tab you are already reading, so nothing about the pages you visit — the text, the address, or the fact that you were there — leaves your browser.

That is meant to be checked rather than believed, and the check needs nothing but the file you just installed. Unzip this add-on and search its scripts: the one that reads your pages contains no fetch, no XMLHttpRequest, no WebSocket and no web address at all. Mozilla's reviewers see the full source for every release, and the build is reproducible, so what they reviewed can be rebuilt and compared against what is served here.

To move to another browser, or to keep a backup, the settings page has Export and Import. Everything Sparkle knows about you is in that one file and nowhere else — which also means uninstalling deletes it.

How much Chinese appears is a five-position control in the toolbar popup, from Subtle to Immersive, and Sparkle can be switched off for one site or for all of them.

Word meanings are adapted from CC-CEDICT, under CC BY-SA 4.0.