Stack Overflow has a new "Run snippet" button

2 min. read

Caution! This article is 8 years old. It may be obsolete or show old techniques. It may also still be relevant, and you may find it useful! So it has been marked as deprecated, just in case.

As every other developer and their dog, I crash from time to time in SO for answers to questions of Life, the Universe and Everything Else.

The other day I came across a question that had a button I hadn't seen before. The button was below a code snippet, and when I clicked it, the snippet executed against an HTML5 sandboxed iframe inserted in the post:

Stack Overflow new run snippet button

I found this so AWESOME that I had to search the origins of it. And I fell into this Stack Overflow post that explains it all.

When I read how they do it, it reminded me of a recent CodePen podcast where the creators of the site explained how they create a secure environment for the execution of scripts. Basically:

  • They use HTML5 sandboxed iframes in order to prevent many forms of malicious attack.
  • They render the Snippets on an external domain ( in order to ensure that the same-origin policy is not in effect and to keep the snippets from accessing your logged-in session or cookies.

It's gonna be great to be able to see the results of a snippet without having to copy and paste and save and compile and run in your own computer :-)