Manabuneko

ManabuNeko helps you remember words while you browse.
It automatically surfaces words you want to learn, shows definitions (and reading support for languages like Japanese/Chinese/Korean/Hindi), and gives you quick practice through flip cards, quiz, and matching test modes.

Instead of opening separate apps, you can save words from any page, review them in small sessions, and reinforce memory with spaced repetition-style practice prompts.
It also supports custom learning links (for example, pronunciation/search resources), so one click opens all your preferred study tools for the current word.

Install ManabuNeko if you want lightweight, in-browser vocabulary practice that fits into normal web usage and helps turn “I saw this word before” into long-term recall.