concurrently
Run multiple commands concurrently in a single terminal. The standard npm development tool for running parallel processes — typically used to start frontend dev server and backend API server simultaneously (concurrently 'npm run frontend' 'npm run backend'). Shows prefixed color-coded output per process, kills all processes when one exits (or crashes), and supports kill-others-on-fail for fail-fast development workflows. Also available as a Node.js API for programmatic use.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Development tool — no production security concerns. Runs local commands only. Process isolation at OS level.
⚡ Reliability
Best When
You're setting up npm scripts for local development and need to run multiple dev servers/watchers simultaneously with clean multiplexed terminal output.
Avoid When
You need production process management, task dependency graphs, or anything beyond simple parallel dev-time commands.
Use Cases
- • Start multiple dev servers simultaneously (React frontend + Node.js API + database) with a single 'npm run dev' command
- • Run watch mode for TypeScript compilation alongside tests in watch mode during development
- • Execute parallel npm scripts with prefixed output so log lines are identifiable by process
- • Implement fail-fast dev setups where killing one process (e.g., server crash) kills all related processes
- • Run agent development tools in parallel (LLM proxy, local API, file watcher) with a single terminal command
Not For
- • Production process management — use PM2, systemd, or Docker for production; concurrently is for development
- • Complex task orchestration with dependencies — use Nx, Turborepo, or Make for task graphs with dependencies
- • Long-running production services — use proper process supervisors for reliability
Interface
Authentication
No authentication — development CLI tool.
Pricing
Fully free, MIT licensed.
Agent Metadata
Known Gotchas
- ⚠ Commands with spaces must be quoted — 'npm run build --watch' vs npm run build --watch; shell quoting in package.json scripts requires escaping
- ⚠ --kill-others-on-fail causes all processes to die when one exits with non-zero code — useful for development but may hide errors if one process fails silently
- ⚠ Windows compatibility: use double quotes for command strings in package.json on Windows; shell quoting differences cause cross-platform script issues
- ⚠ Output interleaving: high-throughput processes can produce interleaved output — use --prefix-length or --timestamp for better log line identification
- ⚠ Process order in output: concurrently assigns colors by index — first command is always color[0]; document which index maps to which process for team clarity
- ⚠ Signal handling: on Ctrl+C, concurrently sends SIGTERM to all processes — ensure dev servers handle graceful shutdown or have their own cleanup
Alternatives
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Scores are editorial opinions as of 2026-03-07.