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BreezingForms is a well established Joomla form builder from Crosstec. Advertising features such as multi page forms, responsive forms, upload progress, and numerous third party integrations, it is a powerful form builder extension. They do offer a free version that includes the core features, but misses out on some of the advanced input elements, and all of the integrations, however it would be perfectly suitable if you don't need anything fancy done with your form responses.
The POWR Form Builder is a modern looking form builder that's offered on a number of platforms including Joomla. The different subscription levels are restrictive in the number of submissions you can accept (apart from the Business plan), and depending on your use case, this could prove rather limiting.
RSForm!Pro has been around since 2009, so it's one of the oldest form builder extensions available for Joomla. It has had some 1.4m downloads from the Joomla Extension Directory, so is also one of the more widespread. As with the others, we have a free but rather limited version on the Joomla Extension Directory, and a premium version available directly from RSJoomla. The premium version is more generous than some others - there are no restrictions on the number of submissions even in the most basic subscription.