Sudoku Play per Ivan Lukichev

Sudoku Play is a small browser extension that lets you solve fast Sudoku mini levels in the popup and continue into a full 9x9 board when you want more.

From the popup you can:

play 10 built-in 4x4 mini levels
continue to the next level after each solved grid
open the full 9x9 Sudoku board inside the extension
open the daily shared puzzle on the website
jump to Kids Sudoku on the website
visit the Sudoku Guide
The extension keeps the interface simple, clean, and focused. It is built for players who want a quick brain break in the popup, with an easy path to a larger Sudoku session afterward.