How to post file via POST API : /entity/file

Facing the same issue.

Use right endpoint like this and set permissions on media type settings:

axios.post('/file/upload/media/YOUR_MIDIA_TYPE_ID/field_media_video_file?_format=json', e.target.result, {
  headers: {
    'Content-Type': 'application/octet-stream',
    'Content-Disposition': `file; filename="${filename}"`,
    'X-CSRF-Token': response.data,
  }
})