Attention! CAPTCHA requires server with an installed library FreeType library and GD Library (imagecreatetruecolor and imagejpeg functions). Available options can be found at the Control Panel's System check page.
The CAPTCHA form (Settings > System settings > CAPTCHA) configures protection from unauthorized automatic registration.
Preset field selects already existing settings or allows manually set up CAPTCHA display parameters in the successive fields below.
CAPTCHA must be configured to eliminate, if possible, automatic recognition. However, it's necessary to search for middle ground between spam protection and user inconvenience. Recommended parameters:
еext transparency (percents) - 40-50%,
vertical rotation angle: from -30 to 30,
add nonlinear distortions,
It's preferable to change the
User fonts can be uploaded to the folder /bitrix/modules/main/fonts/. System supports file fonts in *.ttf format. Some fonts may be displayed incorrectly!
To avoid significant inconvenience for users, you can limit accessible characters to digits only.
Below are CAPTCHA examples that complicate automatic recognition: