View Source

Custom field ID (e.g customfield_13244) is a unique identifier of a field that can be used to update field value via Jira REST API or other way.

There are a few ways to find the custom field ID:

Old Issue View

Open the Old Issue View page (available from the "..." menu in the top right corner of the New Issue View page).

customfield_10159 visible on the screenshot below is the ID you are looking for:

Issue Checklist Documentation (Legacy) > Find custom field ID > image2020-12-15_14-36-31.png

Steps to get Jira custom field ID if you can access Jira administration section:

Navigate to Jira Settings >> Issues >> Custom Fields.
Click the cog (three dots menu button) and hover over Configure or Edit details option.
Observe the URL at the bottom left of the browser window. Example:

The id for this custom field is customfield_10006.

Issue Checklist Documentation (Legacy) > Find custom field ID > image2021-1-2_10-47-24.png

The API endpoint that allows getting the list of the custom fields along with their IDs:

curl https://Your-Jira-URL/rest/api/2/field