Node.js has a set of core modules that are part of the platform and come with the Node.js installation.

We have a lot of them:

Name Description
assert provides a set of assertion functions useful for testing
buffer provides the ability to handle buffers containing binary data
child_process provides the ability to spawn child processes
console provides a simple debugging console
cluster allows to split a Node.js process into multiple workers to take advantage of multi-core systems
crypto provides cryptographic functionality
dgram provides an implementation of UDP Datagram sockets
dns provides name resolution and DNS lookups
events provides an API for managing events
fs provides an API for interacting with the file system
http provides an HTTP client/server implementation
http2 provides an HTTP/2 client/server implementation
https provides an HTTPS client/server implementation
net provides an asynchronous network API
os provides operating system-related utility methods and properties
path provides utilities for working with file and directory paths
perf_hooks to enable the collection of performance metrics
process provides information about, and control over, the current Node.js process
querystring provides utilities for parsing and formatting URL query strings
readline provides an interface for reading data from a Readable stream
repl provides a Read-Eval-Print-Loop (REPL) implementation that is available both as a standalone program or includible in other applications
stream an abstract interface for working with streaming data
string_decoder provides an API for decoding Buffer objects into strings
timers provide functions to schedule functions to be called at some future period of time
tls provides an implementation of the Transport Layer Security (TLS) and Secure Socket Layer (SSL) protocols
tty provides functionality used to perform I/O operations in a text terminal
url provides utilities for URL resolution and parsing
util supports the needs of Node.js internal APIs, useful for application and module developers as well
v8 exposes APIs that are specific to the version of V8 built into the Node.js binary
vm enables compiling and running code within V8 Virtual Machine contexts
wasi provides an implementation of the WebAssembly System Interface specification
worker enables the use of threads that execute JavaScript in parallel
zlib provides compression functionality

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