Postman send json for all your request as default

Postman App>
Collections >
New Collection >
Pre-request Scripts >
Paste this >
pm.request.headers.add({key: 'Accept', value: 'application/json' });
pm.request.headers.add({key: 'Content-Type', value: 'application/json' });

New collection name>
Add request >
Choose your name >
Call your ws>

Every call will now use the json format!