Snap! (formerly BYOB) is a visual, drag-and-drop programming language. It is an extended reimplementation of Scratch (a project of the Lifelong Kindergarten Group at the MIT Media Lab) that allows you to Build Your Own Blocks. It also features first class lists, first class procedures, and continuations. These added capabilities make it suitable for a serious introduction to computer science for high school or college students.

Snap! runs in your browser. It is implemented using Javascript, which is designed to limit the ability of browser-based software to affect your computer, so it’s safe to run even other people’s projects, even if you don’t trust our competence or good intentions.

Snap! is presented by the University of California at Berkeley. It was developed by Jens Mönig at MioSoft Corporation, with design input and documentation by Brian Harvey at Berkeley, and contributions by students at Berkeley and elsewhere.

This material is based partly upon work supported by the National Science Foundation under Grant No. 1138596. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Resources

Download the SVG Alonzo

Hardware

Device control extensions (must be downloaded to your computer):

Privacy

For research purposes, this site uses Google Analytics to collect aggregate information about, e.g., how often the site is used and what links are followed from it. We do not collect personally identifiable information, but if you have a Gmail account or have ever Googled yourself from your own computer, then, despite their assurances to the contrary, Google does collect such information. We recommend that you use AdBlock Plus, Ghostery, NoScript, and/or Privoxy to protect your browsing privacy. The first two are really easy to install and use; the last two take a bit more effort to whitelist sites you trust. (You might also consider the tracking-free DuckDuckGo search engine.)

See our complete privacy policy.

BJC

Teachers, check out the Beauty and Joy of Computing, an AP CS: Principles course using Snap!.

Sample projects

Converted from Scratch

Converted from BYOB3

New!