If I'm sending form data with Axios, what could cause a 400 error?

When sending form data (using `multipart/form-data`), a 400 error can occur if: 1) Required fields are missing. 2) File uploads are too large (server has a size limit). 3) The file type is not allowed by the server. 4) Incorrect encoding of form data. Ensure your form data is correctly formatted and that the server is configured to handle the expected data.