reCAPTCHA Mailhide allowed users to mask their email address behind a captcha to prevent robots from scraping the email and sending spam. Launched April 1, 2010; shut down March 31, 2018 — it lived 7 years. One of 15 Google products killed in 2018. https://github.com/google/recaptcha/issues/221#issuecomment-409586455 Data: Killed by Google (killedbygoogle.com, MIT).