Heads up! This blog post hasn't been updated in over 2 years. CodePen is an ever changing place, so if this post references features, you're probably better off checking the docs. Get in touch with support if you have further questions.
We’ve long had a setting in the JS editor to stop the JS from executing as you type (as it does by default). Sometimes that can be annoying, for instance, if your Pen is an animated sequence and it keep re-starting over and over and over.
We’ve had a number of requests to extend that behavior to beyond JS. You could easily be building an animation in CSS that you are equally annoying with it starting over again and again. That might even be more common!
So, we’ve changed the auto updating setting to affect all the code your write, not just JS. The setting itself is still under the JS editor.
When auto updating is turned off, there will be a Run button in the header:
Click that to update the preview. We moved it up to the header to make it more clear it is an action for the entire Pen, not just JS.
Hope you find it useful!