How can I determine if my code is inside of an iFrame?

I suppose they aren’t used too much anymore but I’ve started using them as a preview window for my projects page.

It can be handy to act different depending on an iFrame, such as scaling the view port.

You can’t do something like this:

iframe > canvas {
  width: 500px;

canvas {
  width: 100%;

but you can use Javascript inside an iFrame and make the changes within the frame itself, rather than from the outside:

function insideIframe() {
  try {
    return window.self !==;
  } catch (e) {
    return true;

if (insideIframe()) {
  // perhaps change the size of something or just act differently