When building web applications with Node.js, security is not optional—it's fundamental. The flexibility and speed of Node.js make it a top choice for web development, but its asynchronous nature, event-driven design, and huge ecosystem mean you must stay proactive to avoid vulnerabilities. This article provides an actionable overview of security patterns every developer should follow to protect their Node.js applications and user data.

1. Always Validate and Sanitize Input

Never trust data received from clients. Always validate input types, lengths, and patterns before processing. Use well-maintained libraries like validator or Joi to check strings, numbers, and email formats. Sanitize input to remove malicious content, preventing attacks like cross-site scripting (XSS) and SQL injection.

Example:

const validator = require('validator');
if (!validator.isEmail(req.body.email)) {
  return res.status(400).send('Invalid email');