When you need to debug, experiment with, and share short code snippets, sandboxing tools are immensely useful. Also as a web developer, having a place to quickly test code can be extremely handy.
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This article covers some of the best free code sandbox tools for testing, debugging and/or sharing your code.
The PractiCode online code editor is a supplementary tool for Landofcode.com's educational web design materials. This online tool can render HTML, CSS and VBScript.
Google Code Playground is a sandbox tool that gives you the ability to test and experiment with Google's awesome APIs.
Ideone is something more than a pastebin; it's an online compiler and debugging tool which allowsto compile and run code online in more than 40 programming languages.
This free and no-frills tool allows you to rapidly test your HTML markup. It auto-updates the preview pane whenever you change something in the coding pane. It doesn't have any saving and collaboration features, so this one is more of a personal tool.
This online CSS/HTML sandbox tool is a slick way of testing snippets of your style sheet and markup with support for changing the background of the preview pane. You can also maximize the screen viewing size of the preview pane by hiding the HTML and CSS code panes.
JS Fiddle is a free sandbox tool for HTML, CSS and JS that has a wonderful set of features, like the ability to reference popular JS libraries/frameworks like jQuery, YUI and MooTools and an Ajax-request-testing functionality for simulating asynchronous calls for your code.
Jsdo.It has a slick interface, an auto-updating preview pane and the ability to include open source JS libraries. One unique feature is the "Smart phone preview" command that opens a new browser window with the viewport sized equivalently to mobile phones.
Codepad is an online compiler/interpreter, and a simple collaboration tool.
You are most welcome to suggest any additions to this list. You can use the comments box below to make any suggestions.