reCAPTCHA
GitLab leverages Google's reCAPTCHA to protect against spam and abuse. GitLab displays the CAPTCHA form on the sign-up page to confirm that a real user, not a bot, is attempting to create an account.
Configuration
To use reCAPTCHA, first you must create a site and private key.
- Go to the URL: https://www.google.com/recaptcha/admin 
- Fill out the form necessary to obtain reCAPTCHA keys. 
- Login to your GitLab server, with administrator credentials. 
- Go to Applications Settings on Admin Area ( - admin/application_settings)
- Fill all recaptcha fields with keys from previous steps 
- Check the - Enable reCAPTCHAcheckbox
- Save the configuration. 
Enabling reCAPTCHA for user logins via passwords
By default, reCAPTCHA is only enabled for user registrations. To enable it for
user logins via passwords, the X-GitLab-Show-Login-Captcha HTTP header must
be set. For example, in NGINX, this can be done via the proxy_set_header
configuration variable:
proxy_set_header X-GitLab-Show-Login-Captcha 1;In GitLab Omnibus, this can be configured via /etc/gitlab/gitlab.rb:
nginx['proxy_set_headers'] = { 'X-GitLab-Show-Login-Captcha' => 1 }