A mainstay of the page builder marketplace, Divi Builder by Elegant Themes has been around since 2013. The Builder is a component of the Divi Theme, and can only be bought as such, however it is possible to use the builder plugin separately from the theme. It's one of the few page builders that doesn't offer it's license as a yearly subscription, and so depending on your use case, could be more cost effective than some of the others.
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