Which Node.js built-in modules are compatible with Netlify Edge Functions?

Compatibility Overview

Netlify Edge Functions run on Deno, not Node.js. Consequently, standard Node.js built-in modules are not natively available. However, compatibility is achieved through Deno's Node.js compatibility layer using the node: prefix.

Supported Modules

Most common utility modules are compatible when imported with the explicit node: scheme. Common examples include:

• node:path: For file and directory path manipulations.
• node:crypto: For cryptographic functions.
• node:events: For the EventEmitter class.
• node:util: For general-purpose utility functions.

Unsupported Modules

Modules that require direct access to the underlying operating system, low-level system calls, or C++ native addons are unsupported. This includes:

• node:fs: The filesystem is read-only or unavailable in the edge runtime.
• node:child_process: Spawning shells or external processes is prohibited.
• node:http / node:https: These are superseded by the Web Standard Fetch API.

Recommended Alternatives

To ensure maximum performance and stability at the edge, prefer Web Standard APIs or Deno's native implementation over Node shims:

Node.js Module	Edge/Deno Alternative
http / https	fetch(), Request, Response
crypto	Web Crypto API (crypto.subtle)
buffer	Uint8Array or TextEncoder / TextDecoder

Verification Steps

To verify if a specific module is compatible with your current deployment target, use the following approach:

1. Import the module using the prefix: import module from 'node:module_name';
2. Deploy the function to a staging environment.
3. Check the Netlify function logs for Module not found or ReferenceError during the execution phase.

Note: Please specify if you are using a specific version of a third-party library that depends on Node built-ins, as this may require a different bundling strategy (e.g., using an esbuild plugin).