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What's in import.meta?

If you look at the import.meta docs on MDN you'll notice that it says:

The spec doesn't specify any properties to be defined on it, but hosts usually implement the following properties: [url, resolve]

So what is actually in there? MDN is correct in saying url and resolve are usually (always) implemented, but each run-time also sticks some other stuff in there. From my own testing, below are the values that exist for each major runtime.

Browsers​

In my testing, Safari, Chrome, and Firefox all have the same import.meta. They don't add anything extra to MDN's listed properties:

  • url: A full URL to the current module file.
  • resolve: a function that converts a relative module path to a URL using the current module's URL as a base.

MDN browser docs on import.meta.

Node.js​

Node.js v22 has the following:

  • filename: the equivalent of CommonJS's __filename or url.fileURLToPath(import.meta.url).
  • dirname: the equivalent of CommonJS's __dirname or path.dirname(import.meta.filename).
  • resolve: the same as in browsers.
  • url: the same as in browsers. Note that this uses a file:// URL while dirname and filename are absolute paths (they start with /).

Node.js docs on import.meta.

Deno​

Deno v1.45 has the following:

  • main: a boolean indicating "whether the current module is the entry point to your program". This is the equivalent of CommonJS's require.main === module check.
  • filename: the same as in Node.js.
  • dirname: the same as in Node.js.
  • resolve: the same as in browsers.
  • url: the same as in browsers.

Deno docs on import.meta.

Bun​

Bun v1.1 has the following:

  • dir: the same as dirname.
  • file: the same as filename.
  • path: the same as filename.
  • require: this is undocumented but appears to be CommonJS's require function.
  • resolveSync: this is undocumented and is an synchronous version of import.meta.resolve. However, since import.meta.resolve is no longer asynchronous, they're the same.
  • env: a reference to process.env.
  • main: the same as in Deno.
  • filename: the same as in Node.js.
  • dirname: the same as in Node.js.
  • resolve: the same as in browsers.
  • url: the same as in browsers.

Bun docs on import.meta.