How to get customfield-id (key) of a Jira field

  1. Use Chrome (because nice formatting of JSON data)
  2. Login into your Jira (as you would normally do)
  3. Open the URL: https://<your-jira-url>/rest/api/2/field
  4. Search (cmd+f) on the the page for your desired field.
  5. You now see the key of your Jira field