Shieldy

Shieldy does one job and does it well: when someone joins your group, it silences them and asks them to pass a check — press a button, solve simple math, or answer a custom question you set — within a time limit. Anyone who fails or ignores it gets removed automatically, which stops the flood of bot accounts that join and immediately start posting spam or links.

Because it focuses only on the join moment, it pairs naturally with a behaviour-focused moderation bot like Rose or GroupHelp for ongoing message filtering. Setup is a single admin invite with no external dashboard, and it remains one of the most recommended captcha bots in independent comparisons of the category.