Azion Runtime and Node.js API compatibility

Explore the compatibility and integration of Node.js APIs and polyfills with the Azion Runtime, enhancing JavaScript execution in edge environments.

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Node.js APIs supported in Azion Runtime

The compatibility between Azion Runtime and Node.js is an ongoing task, but a set of Node Runtime APIs are listed and compatible with Azion Runtime. The following list of APIs can be imported inside functions with the standard import syntax:

import { API } from "import-origin";

API	Support Level	Code sample	Comments
async_hooks	🟡 Partially supported	Access code sample	Only AsyncLocalStorage and AsyncResource are implemented.
fs	🟡 Partially supported		Only async methods (check the list below), others through polyfills.
module	🟡 Partially supported		Also supported in local dev through polyfills (check table below).
process.env	🟢 Supported Supported	`process.env.VAR_NAME`	Other features supported through polyfills (check table below).
url	🟡 Partially supported		Only global `URL` and `URLSearchParams`.

File System (FS) module support

The Azion Runtime provides native support for the File System (FS) module, allowing you to interact with the file system within your functions.

Async:

Method	Parameters	Description
`fs.lstat`	`path`, `options` (optional), `callback`	Gets information about the file or directory.
`fs.mkdir`	`path`, `options` (optional), `callback`	Creates a directory.
`fs.stat`	`path`, `options` (optional), `callback`	Gets information about the file or directory.
`fs.writeFile`	`file`, `data`, `options` (optional), `callback`	Writes data to a file.
`fs.readFile`	`path`, `options` (optional), `callback`	Reads the contents of a file.
`fs.readdir`	`path`, `options` (optional), `callback`	Reads the contents of a directory.
`fs.writeFileSync`	`file`, `data`, `options` (optional)	Writes data to a file synchronously.
`fs.rename`	`oldPath`, `newPath`, `callback`	Renames a file or directory.
`fs.realpath`	`path`, `options` (optional), `callback`	Resolves the absolute path of a file.
`fs.copyFile`	`src`, `dest`, `mode` (optional), `callback`	Copies a file.
`fs.cp`	`src`, `dest`, `options` (optional), `callback`	Copies files and directories.
`fs.read`	`fd`, `buffer`, `offset`, `length`, `position`, `callback`	Reads data from a file.
`fs.read`	`fd`, `buffer`, `options` (optional), `callback`	Reads data from a file.
`fs.read`	`fd`, `options` (optional), `callback`	Reads data from a file.
`fs.rmdir`	`path`, `options` (optional), `callback`	Removes a directory.
`fs.utimes`	`path`, `atime`, `mtime`, `callback`	Updates the access and modification times of a file.

Supported Node APIs with polyfills

A polyfill is a code snippet, often used in JavaScript, that brings new features to environments lacking these capabilities. Polyfills are used during build time at Azion and can be configured through the azion.config.js file.

The following Node APIs are supported through polyfills, along with their respective supported methods.

Status legend:

🟢 Supported: the API works normally at runtime.
🟡 Partially supported: only some methods or features are available.
🔴 Build-only: the module is included so the build process completes without errors, but API calls do not work at runtime.

About the Azion Cells runtime environment — Functions on Azion run inside Cells, an isolation environment based on V8 Isolates. Each Cell is a lightweight, secure execution context with no direct access to the underlying operating system.

For multi-tenant security and infrastructure integrity reasons, Cells do not allow:

Access to operating system properties (such as hostname, platform, or CPU/memory information via node:os).
DNS resolution via native system calls (node:dns, node:dns/promises).
Creation of low-level TCP/UDP sockets that require direct syscalls.

Modules marked as 🔴 Build-only are included as stubs to ensure that NPM packages with static dependencies on these modules can be compiled. Calls to these modules at runtime produce no results and may return default values or throw silent errors.

Module	Status
_http_agent	🟡 Partially supported
_http_client	🟡 Partially supported
_http_common	🟡 Partially supported
_http_incoming	🟡 Partially supported
_http_outgoing	🟡 Partially supported
_http_server	🟡 Partially supported
_stream_duplex	🟡 Partially supported
_stream_passthrough	🟡 Partially supported
_stream_readable	🟡 Partially supported
_stream_transform	🟡 Partially supported
_stream_wrap	🟡 Partially supported
_stream_writable	🟡 Partially supported
_tls_common	🟡 Partially supported
_tls_wrap	🟡 Partially supported
assert	🟡 Partially supported
assert/strict	🟡 Partially supported
async_hooks	🟢 Supported
buffer	🟡 Partially supported
child_process	🟡 Partially supported
cluster	🟢 Supported
console	🟢 Supported
constants	🟢 Supported
crypto	🟡 Partially supported
dgram	🟢 Supported
diagnostics_channel	🟢 Supported
dns	🔴 Build-only
dns/promises	🔴 Build-only
domain	🟢 Supported
events	🟢 Supported
fs	🟡 Partially supported
fs/promises	🟡 Partially supported
http	🟡 Partially supported
http2	🟡 Partially supported
https	🟡 Partially supported
inspector	🟢 Supported
inspector/promises	🟡 Partially supported
module	🟡 Partially supported
net	🟡 Partially supported
os	🔴 Build-only
path	🟢 Supported
path/posix	🟡 Partially supported
path/win32	🟡 Partially supported
perf_hooks	🟢 Supported
process	🟡 Partially supported
punycode	🟡 Partially supported
querystring	🟡 Partially supported
readline	🟢 Supported
readline/promises	🟢 Supported
repl	🟡 Partially supported
stream	🟡 Partially supported
stream/consumers	🟡 Partially supported
stream/promises	🟡 Partially supported
stream/web	🟢 Supported
string_decoder	🟢 Supported
sys	🟡 Partially supported
timers	🟡 Partially supported
timers/promises	🟢 Supported
tls	🟡 Partially supported
trace_events	🟢 Supported
tty	🟢 Supported
url	🟢 Supported
util	🟡 Partially supported
util/types	🟡 Partially supported
v8	🟢 Supported
vm	🟢 Supported
wasi	🟢 Supported
worker_threads	🟡 Partially supported
zlib	🟢 Supported

You can check the list of APIs resolved through polyfills in Azion Bundler’s repository, as well as contribute with the project.

For additional compatibility information:

Go To Supported Web APIs Go To Supported Web Frameworks