What is PM2 and what does it do for Node.js applications?

Updated

PM2 is a daemon process manager for Node.js that keeps your application running 24/7. It fits any Node.js project that needs to stay online in production — from a single Express API on one server to a clustered app across multiple CPU cores. You install it globally with npm install pm2 -g and start an app with pm2 start app.js.

What problem PM2 solves

A Node.js process started with node app.js dies when the terminal closes, crashes on an unhandled error, and uses only one CPU core. PM2 runs your app as a background daemon, restarts it after crashes, and can spread it across all cores. That is the core value: your app stays up without you babysitting the process.

Core capabilities

Capability What it does
Process management Runs apps as background daemons and restarts them on crash
Cluster mode Runs multiple instances of your app to use multiple CPU cores
Zero-downtime reload Reloads app code without dropping incoming requests
Startup scripts Generates a system startup script so apps come back after a reboot
Log management Collects and manages application logs
Watch & reload Restarts the app when source files change (useful in development)
Max memory reload Restarts an instance when it exceeds a memory threshold
Deployment workflow Supports deploying and updating apps on servers
Container integration Works inside containerized environments
PaaS compatible Can run on platform-as-a-service setups

The built-in load balancer comes from cluster mode: PM2 distributes traffic across the instances it manages.

Getting started

  1. Install globally: npm install pm2 -g
  2. Start your app: pm2 start app.js
  3. Expected result: the app runs as a daemon and stays online; PM2 prints a process table with status, CPU, and memory.

From there you can add cluster instances, enable watch mode, or set a memory limit for automatic restarts.

Beyond the process manager

PM2 ships with companion products for teams that need visibility and control:

  • PM2 Monitoring Dashboard — tracks bugs and exceptions and sends alerts. It is web-based, and you start monitoring with pm2 monitor. The site cites 50,000+ applications monitored and a 99.9% uptime SLA.
  • PM2 AI Assistant (MCP) — connects Claude, Cursor, or any MCP-compatible assistant to your monitoring data (server status, metrics, logs, exceptions, traces, alerts), secured by OAuth with your PM2.io account. The MCP endpoint is https://mcp.keymetrics.io/mcp, and the site lists 44 AI tools. A sample interaction: asking why an app restarted returns something like "web-api restarted at 03:12 after hitting its memory limit — heap grew to 1.9 GB over 4 hours," and can create an alert (for example, memory > 80% with email notification).
  • PM2 Enterprise Solution — advanced optimization features and dedicated infrastructure workload for critical applications. Pricing and terms are handled through a contact form rather than published on the page.

Is PM2 right for your project?

PM2 is a strong fit if you run Node.js in production and want process supervision, clustering, and zero-downtime reloads without building that infrastructure yourself. It is less relevant for short-lived scripts, serverless functions where the platform manages the lifecycle, or local development where you do not need a daemon.

If you only need crash restarts, the core process manager covers it. If you also need exception tracking, alerting, or AI-assisted debugging over your runtime data, the monitoring dashboard and MCP assistant are the add-ons to evaluate.