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Certain aspects of how ooniprobe operates can be customized. Usually the default values are the best option, so only change these if you really have to.
This is the recommended setting. By using Tor Hidden Service based backends you will be using the Tor Network to submit OONI measurements and to communicate to OONI's control servers. This means that while anyone monitoring your network traffic will be able to tell that you are a Tor user, they will not be able to know that you are communicating with OONI servers. This also means that OONI is not able to identify you.
By using HTTPS based backends you will be submitting the results of OONI measurements and communicating to our control servers via an encrypted HTTPS connection. This means that anyone monitoring your internet connection will be able to know that you are communicating to OONI servers. Use this setting if you would prefer to have better performance, but are not worried about being identified as an ooniprobe user.
When using cloudfronted backends to submit your measurements to OONI, anyone monitoring your internet activity will only see connections to a popular Content Delivery Network (CDN) and not directly to OONI servers. As such they will not be able to directly identify you as an ooniprobe user. This however means that Amazon (or other cloudfronting services) will know your IP and the content of the communication to OONI servers. Use this only if you are worried about your ISP or country knowing that you are an ooniprobe user, but don't want to use Tor.