Cloudflare Turnstile

Launch Lab puts Turnstile on six forms: sign-in, sign-up, forgot password, the anonymous launch review, the coming-soon "notify me" box and the contact form. Each token is tied to the form it was issued for and to the site's hostname, so a token cannot be replayed on another form.

Sign-up and the anonymous review fail closed: if Cloudflare cannot be reached they refuse. The others let the visitor through rather than lose a sign-in to an outage.

It is free, needs no Cloudflare plan and sets no cookie that would need a banner. With no keys nothing is drawn and nothing is checked, which the code says in so many words: the owner can never be locked out.