sync-fetch-undici

Synchronous wrapper around the Fetch API. Uses the builtin version of fetch, based on undici. See sync-fetch for a similar package based on node-fetch.

Install

npm install sync-fetch-undici

In the browser, a browserify bundle can be loaded from CDNs like unpkg.com.

<script src="https://unpkg.com/sync-fetch-undici"></script>
<script src="https://unpkg.com/sync-fetch-undici@VERSION"></script>

Use

const fetch = require('sync-fetch-undici')

const metadata = fetch('https://doi.org/10.7717/peerj-cs.214', {
  headers: {
    Accept: 'application/vnd.citationstyles.csl+json'
  }
}).json()
// arrayBuffer(), blob(), buffer(), json(), and text() supported

Limitations

Node.js

• Does not support Stream or Blob as input body since they cannot be read or serialized synchronously
• Does not support FormData as input body yet as it can contain a Blob
• Does not support signal as it cannot be implemented synchronously; instead does support the non-standard option timeout (a number of seconds)
• undici applies some parts of the specification more suited to browser usage; for example setting the Host header or other "forbidden request headers" is not possible.
• undici versions below 7.20.0 contain a bug breaking redirects of POST and PATCH requests with request bodies. The patched version of undici is shipped starting with Node.js v24.14.0; no backport for v22 has been made.

Browser

• Does not support most options, since XMLHttpRequest is pretty limited. Supported are:
  • method
  • body
  • headers
  • credentials (but not omit)
  • (Non-spec) timeout
• The non-standard buffer() and textConverted() methods are not supported
• CORS limitations apply; note they may be stricter for synchronous requests