c/side is a client-side web security company that focuses on protecting websites from browser-side supply chain attacks, particularly those originating from third-party scripts. The company's core product is a third-party script proxy, performance, and analysis engine that monitors, controls, and secures the behavior of scripts running in users' browsers on behalf of their customers' websites. The platform uses AI to address the complexity and obscurity that has historically made client-side security difficult to implement. By proxying third-party scripts, c/side provides visibility into what those scripts do, enabling detection of malicious or unexpected behavior such as data exfiltration, credential harvesting, or unauthorized tracking — threats commonly associated with web skimming and Magecart-style attacks. c/side targets businesses of all sizes, positioning its solution as accessible regardless of company scale. Every customer receives direct communication access via shared Slack or Microsoft Teams channels, with the company emphasizing rapid response times from its security team. The company also publishes content addressing related compliance topics, including GDPR applicability for websites using third-party tracking scripts, reflecting its focus on data privacy implications of client-side script activity. c/side was founded by senior security engineers with backgrounds at companies including Cloudflare, JP Morgan, Vercel, and Microsoft. The company is backed by venture firms including Scribble Ventures, Roar Ventures, Uncork Capital, and Mantis VC, as well as individual investors from the security and technology industries. It has received recognition from the Cybersecurity Defense Awards for Client-Side Protection and the Forbes 30 Under 30 Europe list.