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Network access

You can access the internet from a Snap using the global fetch API.

Steps​

1. Request permission to access the internet​

Request the endowment:network-access permission, which exposes the global fetch API to the Snaps execution environment. Add the following to your Snap's manifest file:

snap.manifest.json
"initialPermissions": {
  "endowment:network-access": {}
}

2. Use the fetch function​

You can now use the fetch function to access the internet. The following example fetches a JSON file from the provided URL.

index.ts
async function getJson(url: string) {
  const response = await fetch(url)
  return await response.json()
}
Same-origin policy and CORS

fetch requests in a Snap are bound by the browser's same-origin policy. Since Snap code is executed in an iframe with the sandbox property, the browser sends an Origin header with the value null with outgoing requests. For the Snap to be able to read the response, the server must send an Access-Control-Allow-Origin CORS header with the value * or null in the response. Otherwise, you might need to set up a proxy.

caution

XMLHttpRequest isn't available in Snaps, and you should replace it with fetch. If your dependencies use XMLHttpRequest, you can patch it away.

Example​

See the @metamask/network-access-example-snap package for a full example of accessing the internet from a Snap. This example exposes a custom JSON-RPC API for dapps to call the fetch function from a Snap.