Fluid videos with my adaption of FitVids

Embedded videos are not automatically responsive or fluid. They come with a fixed setting for width and height. To make them responsive while keeping aspect ratio, typically they are embedded into a wrapper element. The wrapper receives some clever padding and positioning, and as a last step the fixed dimensions are removed from the video. The technique has been described by Thierry Koblentz in his A List Apart article „Creating Intrinsic Ratios for Video“ in 2009.

To achieve this kind of manipulation automatically for all videos on your website, you have to run a script. Therefore I came up with my own tiny version of the FitVids script. FitVids is Dave Rupert´s implementation of the described algorithm. It has jQuery as a dependency, which I wanted to avoid. Therefore I picked up Dave´s code and simplified it to my needs. No dependencies anymore.

For correct initial rendering on small screens, it is important to set a max-width for IFrames in your CSS, otherwise your text might be rendered too tall on those small screens. That´s because initially, before the script does its work, the IFrame might have too much width and breaks your layout. Setting it to a max-width of 100% ensures it stays within desired limits. However, the adjusting script needs to run afterwards, because otherwise the aspect ratio of the videos would be broken.

iframe {
max-width: 100%;

Place the script on your website by putting it into a file, e.g. fit-vids.js, and reference it via <script src="/.../fit-vids.js"></script>. Here it is:

A tailored version of FitVids,
which is originally created by Dave Rupert (davatron5000).
FitVids again, is based on https://css-tricks.com/fluid-width-video/
by Chris Coyier, which borrows its basic idea from Thierry Koblentz

addEventListener('load', event => {
// List of Video Vendors embeds you want to support
const players = [

// Select videos
const fitVids = document.querySelectorAll(players.join(','));

// If there are videos on the page...
if (fitVids.length) {

// Loop through videos
for (let vid of fitVids) {

// Get Video Information
let width = vid.getAttribute('width');
let height = vid.getAttribute('height');
let aspectRatio = height / width;
let parentDiv = vid.parentNode;

// Wrap it in a DIV
let div = document.createElement('div');
div.style.position = 'relative';
div.style.paddingBottom = aspectRatio * 100 + '%';
div.style.width = '100%';
div.style.height = '0';

vid.style.position = 'absolute';
vid.style.top = '0';
vid.style.left = '0';
vid.style.width = '100%';
vid.style.height = '100%';

parentDiv.insertBefore(div, vid);

// Clear height/width from fitVid