Microfill for gulp

Usage no npm install needed!

<script type="module">
  import gulpMicrofill from '';



Only loads polyfills for the missing gabs

How to install

1. Install gulp CLI
npm install --global gulp
2. Install gulp as a project dependency
npm install gulp --save-dev
3. Install gulp-microfill
npm install gulp-microfill --save-dev

How to use

var gulp = require('gulp');
var microfill = require('gulp-microfill');

gulp.task('default', function() {
        .pipe(microfill(['set-immediate', 'promise', 'fetch', 'collection']))


gulp-microfill takes two arguments, an array with the polyfills and optionally an option object. See microfill for a complete list of all supported polyfills.

The option object may contain:

  • minified (boolean) - Use a minified loader and minified polyfills (if available)
  • fileName (string or function) - The filename used in the loader. This should be relative to the base url of your webpage. If you specify a function, it will be invoked for every file and should return the fileName as a string.

How does it work

Microfill replaces your javascript file with a file that looks like this:

    var hex = 0;

    if (!window.setImmediate) hex += 1 << 0;
    if (!window.Promise) hex += 1 << 1;
    if (!window.fetch) hex += 1 << 2;
    if (!window.WeakMap || !window.Map || !window.Set) hex += 1 << 3;

    var script = document.createElement("script");
    script.src = "file-" + hex.toString(16) + ".js";
    script.type = "text/javascript";

If a feature is missing, hex will be increased by a certain value. Based on the final value of hex a file will be loaded. Microfill generates such file for every possible combination of polyfills that are needed. See the test directory for a sample output.