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Why is the browser environment invisible to WAF monitoring?

Wednesday, September 3rd, 2025

Updated September 5th, 2025

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Simon Wijckmans

A WAF (Web Application Firewall) operates at the perimeter, analyzing traffic as it crosses between external networks and your internal network towards your web servers. The browser environment is a separate execution context that happens on your users' devices, completely outside your network perimeter. Once JavaScript code reaches the browser and begins to execute, it's operating in an environment that your WAF has no visibility into or control over. By design, a WAF is ineffective against client-side threats.

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More About Simon Wijckmans

Founder and CEO of c/side. Building better security against client-side executed attacks, and making solutions more accessible to smaller businesses. Web security is not an enterprise only problem.