What's the difference between client-side security and server-side security?

Server-side security protects your infrastructure with tools like firewalls, a WAF protecting the perimeter against malicious inbound requests, and vulnerability scanners, building a wall around your critical infrastructure. Client-side security protects where your applications actually execute: in your users' browsers. Think of it this way, server-side security protects your kitchen, but client-side security protects the meal after it's served to your customers. You need both layers because attackers increasingly target the client-side, where they can steal data directly from users without touching your servers.