Get SharePoint Role Definition IDs (Out of the box + Custom Permission set)

To assign item level permission we need to have the role definition ids. Here are few out of the box ids below.

Role Definition Name	Role Definition Id
Full Control	1073741829
Design	1073741828
Edit	1073741830
Contribute	1073741827
Read	1073741826
View Only	1073741924

Above Role Definition IDs are found using below REST API only.

Role definition ids of custom permission set can be found out using REST API. I have created a custom permission called “BASIC USER”. Now hit below URL in the browser

https://site-url/_api/web/roledefinitions

You can see the custom permission details including Role Definition ID in the browser response as in below screenshot. I am using online xml beautifier tool for good visibility. It will show role definition ids of all the permission sets (out of the box permissions like full control, read etc as well as custom permissions)