Ask questionsSvelte applications fail to load in IE 11. Similar loading issue with the main site


Digging closer the error is on this line:

const identity = x => x;

I suspect I need a polyfill but there doesn't seem to be an appropriate one. Svelte version: 3.0.0

The home page: gives this error: (as of 30/04/2019)


IE version:



Answer questions assmith

Sorry for appending to a closed thread, but since this is the first hit that comes up when looking for IE11 and Sapper issues I thought I should post here. Sapper uses document.baseURI in goto and prefetch which isn't supported in IE11 and doesn't appear to be polyfilled by Babel or

TypeError: Invalid scheme

is a hint that this might be biting you.

I found this patch which works for me when added to template.html along with the polyfills mentioned in Usage of shimport makes legacy support prohibitively challenging


if ('baseURI' in Node.prototype === false) {
  Object.defineProperty(Node.prototype, 'baseURI', {
    get: function() {
      var base = (this.ownerDocument || this).querySelector('base');
      return (base || window.location).href;
    configurable: true,
    enumerable: true

Maybe a polyfill for this could be added to --legacy builds automatically in a future release?


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