Canadian citizens generally do not require a visa. While some people mistakenly think Canada is part of the VWP, the authorization for Canadian citizens to travel visa-free comes from other immigration laws. The Machine Readable Passport requirement does not apply to Canadian citizens, because they are not part of the VWP.
Note: It should be noted, these Canadian citizens traveling to the U.S. require nonimmigrant visas: Treaty Traders (E), and Fiance/es (K-1), as well as a U.S. citizen's foreign citizen spouse, who is traveling to the U.S. to reside here while they wait for the final completion of the process of immigration (K-3), and their respective children (K-2 for children of fiancés, and K-4 for children of a foreign citizen spouse), spouses of lawful permanent residents (V-1) and the children of those spouses (V-2) traveling to the U.S. to reside here while they wait for the final completion of their immigration process. Additionally, these Canadian citizens traveling to the U.S. require nonimmigrant visas: foreign government officials (A), officials and employees of international organizations (G), NATO officials, representatives and employees if they are being assigned to the U.S. (as opposed to an official trip).
Currently, 27 countries participate in the VWP. The VWP participating countries include:
Andorra, Australia, Austria, Belgium, Brunei, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Ireland, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, The Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, Taiwan, United Kingdom.