captcha_level
The 'captcha_level' directive controls the complexity of the captcha generated for user validation.
Description
The 'captcha_level' directive in the NGINX Captcha Module is used to specify the complexity of the captcha that is generated. This directive accepts a numeric argument that indicates the level of difficulty, allowing administrators to tune the captcha for their specific application needs. A higher level might correspond to a more complex validation, such as a longer string of characters, while lower levels might create simpler captchas.
When this directive is used in an NGINX configuration, the level specified affects how the captcha images are generated and validated. For example, if a level of '3' is set, it could dictate that a captcha must consist of a certain number of confusing or similar characters that are harder for bots to solve, as compared to a level of '1' that might use easier characters or fewer characters. This means that user interaction is required to complete a form, adding a layer of security against automated submission.
Moreover, the 'captcha_level' directive can be placed in the http, server, or location contexts, making it flexible for different usage scenarios depending on where the captcha needs to be applied. However, it should be noted that the effect of this directive also relies on the correct setup of associated parameters such as 'captcha_length' and 'captcha_charset', which define what characters are included in the captcha and how many characters are presented to the user.
Config Example
location =/form {
captcha_level 2;
captcha;
}Ensure that the level value does not exceed what your application can handle, as overly complex captchas may frustrate users.
Always test the captcha generation after changing levels to confirm that it works as expected and is user-friendly.