Ancestry.com and Ancestry.ca It has not been indexed (yet) so researchers can only browse the images for now but Ancestry will be providing an index within a few months. The images are free to view but when the index is ready it will behind a pay-to-view wall.
Those who are not already Ancestry subscribers do need to sign up for free access but no credit card details are required. This is not the same as their 14 day free trial where credit card information is required.
There is some controversy over Library and Archives (LAC) partnership with Ancestry.com and many people are questioning why an American based company has Canadian records, will we see the census on LAC's website at any point, etc.
After looking around, I found the answers to many of those questions here on Collections Canada website at Learn more about the Library and Archives Canada Agreement with Ancestry.ca. It’s a very detailed explanation of the partnership deal between LAC and Ancestry.
Basically Ancestry gets to use the images while they do the indexing.
The images and index are on Ancestry for 3 years then the indexes are
turned over to LAC and they put the index and images online for free.
Seems like a win-win situation to me! If we waited for LAC to index we’d be waiting a very long time!
Interested genealogists can also read "LAC Answers Questions about Release of 1921 Census" on the OGS (Ontario Genealogical Society) Blog.