Node.js node-js
JavaScript runtime built on V8 + libuv. Lifted JS from browser to server-side in 2009. Ryan Dahl created it, the OpenJS Foundation now maintains.
Single-threaded event loop, non-blocking I/O. npm is the package registry (largest in the world). Competitors: Deno (Ryan Dahl's "second try", 2018, safer defaults), Bun (2022, faster, API-compatible). Node 20 LTS (2023) + 22 LTS (2024) are current. Companies on Node: Netflix, LinkedIn, PayPal, Uber, NASA.