What is Concurrently? Run Multiple Commands at the Same Time

What is Concurrently?

A Node.js-based CLI tool that lets you run multiple shell commands in parallel. It's built to keep dev server, mock API, type checker and watcher visible inside a single terminal.

Why Use It?

Modern projects routinely run several processes at once. Concurrently launches them all with one command and makes onboarding easier for new team members.

• Start N processes with a single command
• Colored, labeled logs — clear which line came from where
• Saves time during development
• Great for fullstack and microservice setups
• Simplifies developer experience

Installation

Add it with one line; usually as a dev dependency.

npm install -D concurrently

# or
npm install -g concurrently --version

Basic Usage

Pass quoted commands to concurrently and they all start in parallel.

npx concurrently "npm run dev" "npm run api"

package.json Example

The most common pattern: a root dev script that fans out to sub-scripts via concurrently.

{
  "scripts": {
    "dev": "concurrently \"npm run client\" \"npm run server\"",
    "client": "vite",
    "server": "node db.json --port 3001"
  }
}

Output Behavior

Details that make Concurrently's output easy to read:

• All commands run in parallel
• Logs go to a shared terminal with labels and colors
• Exit codes propagate to the parent process — safe in CI
• Easy to track multiple microprocesses

Common Options

The flags you'll reach for most often:

--names           Assign names to commands
--prefix-colors   Set custom colors for logs
--kill-others     Stop all if one fails
--restart-tries   Retry failed processes
--group           Group output together

Example with Options

Combining names, colors and kill-others gives you a much more readable terminal.

npx concurrently \
  -n CLIENT,API \
  --prefix-colors "cyan.bold,magenta" \
  --kill-others \
  "npm run client" \
  "npm run api"

Sequential Mode

Use --sequential to run commands one after another. This is for step-by-step build/start flows rather than truly parallel work.

npx concurrently --sequential \
  "npm run build" \
  "npm run start"

Use Cases

Real-world scenarios where Concurrently saves the day:

• Running frontend + API server together
• Fullstack development setups
• Microfrontend development
• Running watchers (lint + test) at the same time
• Docker or local dev orchestration

Tips

For a cleaner setup:

• Keep scripts short and readable
• Use --kill-others for safer shutdowns
• Combines great with tools like Vite and JSON Server
• Glob pattern: "npm:dev:*" matches every dev: script automatically

Summary

Concurrently simplifies running multiple commands, improves terminal organization and is essential for modern dev workflows. It's lightweight, fast and easy to use — and noticeably improves team onboarding.