Mem0 is the most widely adopted memory framework for developers, with a large open-source community and a hosted API. You import the SDK and call it from your own application; your users never see Mem0 directly. It is infrastructure, not an end-user product.
ChatGPT’s memory is built into ChatGPT and locked to OpenAI. It is convenient inside ChatGPT but capped at roughly 1,400 words, with no structured export and no way to use it in another model.
If your goal is "memory I can use across tools without writing code", neither Mem0 nor ChatGPT’s built-in memory is ideal: Mem0 needs development, ChatGPT’s is provider-locked. Alma is a finished product that gives you a portable memory layer plus chat, studios and calendar, and reaches Claude Desktop, Cursor and VSCode over MCP.