From my the information I have read on Internet, it seems like Brazil covers a good part of the alphabet when it comes to power outlet types.
What type of power outlets should I expect in hotels in Sao Paulo and Rio de Janeiro?
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In 2009, in a not smart act, the brazilian governament created a new standard that's different from all other countries in the world:
This image shows the brazillian standard at the bottom and the number of countries (países, in red) that use each other standard.
That said, it is still very common to find the american standard (second one) and mainly the "universal" plug (last one). Actually the most common is to find a plug using the universal without the ground port, so you'd need an adapter anyway.
Post 2009 buildings are required to use the new standard, while older buildings were not required to change existing plugs, so it doesn't depend on where you go (São Paulo/Rio or the rest), but when the hotel was created/renovated.
That is such a hassle that every hotel must be prepared to have adapters for their guests, I wouldn't worry if I my things use the american standard, but I guess I would buy one adapter to the american or universal or brazilian standard if using the other standards.