About this documentation
Welcome to the official API reference documentation for Node.js!
Node.js is a JavaScript runtime built on the V8 JavaScript engine.
Contributing
Report errors in this documentation in the issue tracker. See the contributing guide for directions on how to submit pull requests.
Stability index
Throughout the documentation are indications of a section's stability. Some APIs are so proven and so relied upon that they are unlikely to ever change at all. Others are brand new and experimental, or known to be hazardous.
The stability indexes are as follows:
[Stable: 0 - Deprecated]
Stable: 0 Stability: 0 - Deprecated. The feature may emit warnings. Backward compatibility is not guaranteed.
[Stable: 1 - Experimental]
Stable: 1 Stability: 1 - Experimental. The feature is not subject to semantic versioning rules. Non-backward compatible changes or removal may occur in any future release. Use of the feature is not recommended in production environments.
[Stable: 2 - Stable]
Stable: 2 Stability: 2 - Stable. Compatibility with the npm ecosystem is a high priority.
[Stable: 3 - Legacy]
Stable: 3 Stability: 3 - Legacy. Although this feature is unlikely to be removed and is still covered by semantic versioning guarantees, it is no longer actively maintained, and other alternatives are available.
Features are marked as legacy rather than being deprecated if their use does no harm, and they are widely relied upon within the npm ecosystem. Bugs found in legacy features are unlikely to be fixed.
Use caution when making use of Experimental features, particularly when authoring libraries. Users may not be aware that experimental features are being used. Bugs or behavior changes may surprise users when Experimental API modifications occur. To avoid surprises, use of an Experimental feature may need a command-line flag. Experimental features may also emit a warning.
Stability overview
| API | Stability |
|---|---|
| Assert | (2) Stable |
| Async hooks | (1) Experimental |
| Asynchronous context tracking | (2) Stable |
| Buffer | (2) Stable |
| Child process | (2) Stable |
| Cluster | (2) Stable |
| Console | (2) Stable |
| Crypto | (2) Stable |
| Diagnostics Channel | (2) Stable |
| DNS | (2) Stable |
| Domain | (0) Deprecated |
| File system | (2) Stable |
| HTTP | (2) Stable |
| HTTP/2 | (2) Stable |
| HTTPS | (2) Stable |
| Inspector | (2) Stable |
Modules: node:module API | (1) .2 - Release candidate (asynchronous version) Stability: 1.1 - Active development (synchronous version) |
| Modules: CommonJS modules | (2) Stable |
| Modules: TypeScript | (1) .1 - Active development |
| OS | (2) Stable |
| Path | (2) Stable |
| Performance measurement APIs | (2) Stable |
| Punycode | (0) Deprecated |
| Query string | (2) Stable |
| Readline | (2) Stable |
| REPL | (2) Stable |
| Single executable applications | (1) .1 - Active development |
| SQLite | (1) .1 - Active development. |
| Stream | (2) Stable |
| String decoder | (2) Stable |
| Test runner | (2) Stable |
| Timers | (2) Stable |
| TLS (SSL) | (2) Stable |
| Trace events | (1) Experimental |
| TTY | (2) Stable |
| UDP/datagram sockets | (2) Stable |
| URL | (2) Stable |
| Util | (2) Stable |
| VM (executing JavaScript) | (2) Stable |
| Web Crypto API | (2) Stable |
| Web Streams API | (2) Stable |
| WebAssembly System Interface (WASI) | (1) Experimental |
| Worker threads | (2) Stable |
| Zlib | (2) Stable |
JSON output
Added in: v0.6.12
Every .html document has a corresponding .json document. This is for IDEs and other utilities that consume the documentation.
System calls and man pages
Node.js functions which wrap a system call will document that. The docs link to the corresponding man pages which describe how the system call works.
Most Unix system calls have Windows analogues. Still, behavior differences may be unavoidable.