How to Build Your First Secure Web Application

Security should not be an afterthought. Learn how to architect full-stack apps with secure headers, CSRF guards, and sanitized inputs from day one.

# How to Build Your First Secure Web Application

Most developers learn to code first, and only worry about security after their database gets leaked or user sessions get hijacked.

Building secure web applications from day one requires adhering to 5 core design tenets: 1. **Never Trust User Input**: Sanitize, validate with Zod or Joi schemas on the server, and use parameterized queries. 2. **Implement Strict Content Security Policy (CSP)**: Disallow inline script execution to neutralize 95% of reflected and stored XSS vectors. 3. **Use HTTP-Only and SameSite Cookies**: Never store sensitive auth tokens in localStorage where rogue third-party scripts can extract them. 4. **Rate Limit Sensitive Routes**: Protect login, password reset, and payment endpoints against credential stuffing and brute-force attacks. 5. **Keep Dependencies Audited**: Run `npm audit` regularly to spot outdated packages with known CVEs.