JS check for every user - These challenges may disincentivize automated traffic from accessing your site by requiring the use of additional computational resources. Note: Defeating Bots may affect some actions on your website and/or non-automated traffic. For example, it may block access to your APIs and prevent access from mobile applications.
Its new “bot fight mode,” which Cloudflare today enabled as a free opt-in feature for all accounts, will detect and serve bots with deliberately computationally intensive challenges. As the bot tries to crunch the impossible puzzle — effectively a small bit of code only visible to the bot — the bot’s server will max out its processing power, churning up cloud resources and driving up costs for the bot operator.