Why you cannot just move it
ChatGPT's memory is a feature inside one product. You cannot open it, copy it, or hand it to another assistant. When you request your ChatGPT data export, the download includes your conversations but not the personal memories ChatGPT built up about you. There is no file to import into Claude or Gemini.
That is why there is now a small genre of guides explaining how to copy your ChatGPT memory across by hand: open the memory settings, read each entry, and retype it into the next assistant. It works once, badly, and you are locked in again the moment the new assistant starts its own private memory.
The fix: own your memory once, do not move it forever
The durable answer is to stop keeping memory inside any one assistant. Write the facts that matter, your projects, preferences, decisions, and context, into notes you control. Then connect every assistant to those notes through Hjarni's built-in MCP server. Each one reads the same memory, and any of them can write back.
After that there is no transfer to do again. Switching from ChatGPT to Claude, or adding Gemini, means connecting the new assistant to notes that already exist. The memory outlives whichever tool is in fashion.