unfetch

library5.0.0jsnpmunverified

A minimal 500-byte fetch polyfill that provides a subset of the standard fetch API. Version 5.0.0 is the current stable release, maintained infrequently as it is feature-complete. Unlike larger alternatives (e.g., whatwg-fetch), unfetch focuses on bare-bones functionality: it only supports text and JSON responses, uses Arrays instead of Iterables, and has no streaming support. It works as both a polyfill (auto-installs on window.fetch) and a ponyfill (importable function). TypeScript types are included. Requires a Promise polyfill for IE11 and below.

testing

npm install unfetch

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · UNFETCH

unfetch

testingjavascriptv5.0.0

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

fetch (polyfill)

✓ import 'unfetch/polyfill'

✗ import fetch from 'unfetch/polyfill'

Polyfill mode auto-installs fetch on window. No need to import a symbol. (ESM)

fetch (ponyfill)

✓ import fetch from 'unfetch'

✗ import { fetch } from 'unfetch'

Ponyfill mode returns a local fetch function; it is a default export.

fetch (CommonJS ponyfill)

✓ const fetch = require('unfetch')

✗ const { fetch } = require('unfetch')

CommonJS require yields the default export as the entire module.

Demonstrates basic fetch usage with unfetch as a ponyfill for typed environments.

import fetch from 'unfetch'; fetch('https://api.example.com/data') .then(response => { if (!response.ok) throw new Error('Network response was not ok'); return response.json(); }) .then(data => console.log(data)) .catch(err => console.error('Fetch failed:', err)); // Using the polyfill (global): // import 'unfetch/polyfill'; // fetch('/relative/path').then(r => r.text()).then(console.log);

Debug

Known issues

gotchaunfetch does not support streaming responses (e.g., response.body is undefined).

fix

Use alternatives like whatwg-fetch if streaming is required.

affects: >=1.0.0

gotchaunfetch does not support the full Fetch spec: no Request, Response, Headers constructors, no AbortController, no credentials option.

fix

Use a more complete polyfill if those features are needed.

affects: >=1.0.0

gotchaunfetch returns a Promise that resolves to a response with only ok, status, statusText, headers (Map-like), text(), json(), and headers.get() methods.

fix

Do not rely on blob(), arrayBuffer(), formData(), or other methods.

affects: >=1.0.0

gotchaIn polyfill mode, unfetch may override existing window.fetch even if it is a native implementation (it checks for fetch, but may override a non-standard implementation).

fix

Use ponyfill mode if you need to preserve an existing fetch implementation.

affects: >=1.0.0

gotchaunfetch requires a global Promise to be available for older browsers (IE11 and below).

fix

Include a Promise polyfill (e.g., es6-promise) before unfetch.

affects: >=1.0.0

deprecatedThe UMD bundle (unfetch/dist/unfetch.umd.js) is deprecated in favor of ESM or the polyfill script.

fix

Use import 'unfetch/polyfill' or <script src="https://unpkg.com/unfetch/polyfill"></script>.

affects: >=4.0.0

Errors

Common errors & fixes

Uncaught TypeError: Failed to fetch

unfetch's fetch throws a TypeError for network errors, but the message varies across browsers.

fix

Catch the error and check the message pattern; or use the ponyfill which rejects with a TypeError.

Import 'unfetch/polyfill' does not export 'fetch'

The polyfill module does not have a default export; it only side-effects.

fix

Use import 'unfetch/polyfill' (no symbol) to apply the polyfill globally.

TypeError: response.json is not a function

Response object from unfetch does not have json() if it's not a valid response (e.g., network error).

fix

Check response.ok before calling response.json().

Uncaught (in promise) TypeError: response.headers.get is not a function

In older versions of unfetch (< 4.0.0), headers object might be missing or not iterable.

fix

Update to unfetch@5 or access headers as a plain object via response.headers property.

Upgrade

Version history

5.0.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

10 hits · last 30 days

node

Resources

githubhttps://github.com/developit/unfetch ↗

packageunfetch ↗

homepagehttps://github.com/developit/unfetch ↗