You do PUT when you want to set the _id : PUT index/_doc/1 { ... } You do POST when you don't want to set the _id and let elasticsearch generate it: POST index/_doc { ... }

The key difference between PUT and POST methods is that a PUT is restricted to create or update operations, while a POST operation may perform any type of processing. Unlike a POST, PUT operations may only operate on the resource identified by the URL provided.

The PUT method is used to modify a single resource. The POST method is used to add a child resource. It can be cached.

The HTTP request POST method sends data to a server in a request body. HTML form data is typically sent to the server using a POST request. The server can use this data to add the sent data to a database. The HTTP PUT method is used to create a new resource or replace a resource.