Load a character exported from D&D Beyond's character service API. Everything stays in your browser — no data leaves this page.
https://character-service.dndbeyond.com/character/v5/character/<ID> — the ID is in your normal character URL, and the character must be set to public. Save the response as a .json file and drop it above. (Direct fetch from this page can be blocked by browser cross-origin rules — the file drop always works.)