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eqio logo


A simple, tiny alternative to element/container queries

eqio allows you to attain the holy grail of responsive web development/design systems: components that can adapt their styling based on their width, not the browser‘s.

It uses IntersectionObservers under-the-hood (so is well supported in “good” browsers and easily polyfilled in others) to apply appropriately named classes to the component when necessary.

Table of Contents


A complete demo is available here:



npm install eqio --save

Direct <script> include

<script src=""></script>



  1. Add a class of eqio to the element.
  2. Add a data-eqio-sizes attribute whose value is a JSON-serializable array of sizes.
  3. Optionally add a data-eqio-prefix attribute whose value is used as the prefix for your class names.
  class="media-object eqio"
  data-eqio-sizes='["<400", ">700"]'

The above component will:

  • be able to be customised when its width is 400 or smaller ("<" is a synonym for max-width, not “less than”).
  • be able to be customised when its width is 700 or greater (">" is a synonym for min-width, not “greater than”).
  • apply the following classes media-object-eqio-<400 and media-object-eqio->700 as appropriate. If data-eqio-prefix had not been specified, the applied classes would be eqio-<400 and eqio->700.

Note: Multiple classes can be applied at once.


In your CSS, write class names that match those applied to the HTML.

.media-object-eqio-\<400 {
  /* customizations when less than or equal to 400px */

.media-object-eqio-\>700 {
  /* customizations when greater than or equal to 700px */


  • eqio classes include the special characters < & >, so they must be escaped with a \ in your CSS.
  • eqio elements are position: relative by default, but your component can override that to absolute/fixed etc as required.
  • eqio elements can't be anything but overflow: visible.
  • To prevent accidental creation of horizontal scrollbars, a parent element is required to overflow-x: hidden. It is recommended to apply this to body.

The JavaScript

If using a module bundler, such as webpack, first import Eqio.

import Eqio from 'eqio';

In your JS, tell eqio which elements are to be made responsive by passing a DOM reference to Eqio.

var mediaObject = new Eqio(document.querySelector('.media-object'));

Should you need to stop this element from being responsive, you can call .stop() on your instance:


This will remove all observers and eqio internals, except for the class names that were applied at the time.

Copyright (c) 2018 Matt Stow
Licensed under the MIT license (see LICENSE for details)