OKMindmap is described as 'Free, collaborative mind-mapping tool with support for SVG and multi-presentation conversion' and is a Mind Mapping Tool in the Office & Productivity category. There are six alternatives to OKMindmap, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac, iPhone and iPad. The best alternative is XMind. It's not free, so if you're looking for a free alternative, you could try Wondershare Edraw MindMaster or Heimer. Other great sites and apps similar to OKMindmap are ThinkSpace : Mind Map & Note (Freemium), Xmind 2020 (Paid) and Brainio (Paid).
Heimer is a desktop application for creating mind maps and other suitable diagrams. It's written in Qt and targeted for Linux and Windows. Features: Easy-to-use UI Very fast Zoom in/out/fit Zoom with mouse wheel Save/load in XML-based .