Stop Spam. Read Books.

Over 60 million CAPTCHAs are solved every day by people around the world. reCAPTCHA channels this human effort into helping to digitize books from the Internet Archive. When you solve a reCAPTCHA, you help preserve literature by deciphering a word that was not readable by computers. Learn more.

reCAPTCHA is a project of the School of Computer Science at Carnegie Mellon University.

Credits

• Luis von Ahn — executive producer.
• Ben Maurer — software architect.
• Colin McMillen — software architect.
• Mike Crawford — plugin development, system administration, documentation.
• Ryan Staake — graphic design.
• Manuel Blum — helpful ideas, advice, and encouragement.

Sponsors

• Intel donated servers and equipment.
• Novell donated SUSE Enterprise Linux licenses that power our servers.
• The MacArthur Foundation gave Luis von Ahn a fellowship.
• ALADDIN / Olympus supported this project.

Open Source

reCAPTCHA is mostly powered by open source software. We'd like to thank all open source developers for creating tools that help in developing applications such as ours, but especially the developers of:

• lighttpd — the blazing fast webserver that powers reCAPTCHA.
• MySQL — helps us keep track of books and words.
• Thrift — an RPC framework that allows for easy versioning
• Python — most of reCAPTCHA is written in Python.
• Python Imaging Library — powers the distortions of our visual captchas.
• Django — powers our system administration website.
• SoX — powers our audio captchas.