# Optional HTTP headers
EventStoreDB supports custom HTTP headers for requests. The headers were previously in the form X-ES-ExpectedVersion but were changed to ES-ExpectedVersion in compliance with RFC-6648 (opens new window).
The headers supported are:
| Header | Description |
|---|---|
| ES-ExpectedVersion | The expected version of the stream (allows optimistic concurrency) |
| ES-ResolveLinkTo | Whether to resolve linkTos in stream |
| ES-RequiresMaster | Whether this operation needs to run on the master node |
| ES-TrustedAuth | Allows a trusted intermediary to handle authentication |
| ES-LongPoll | Instructs the server to do a long poll operation on a stream read |
| ES-HardDelete | Instructs the server to hard delete the stream when deleting as opposed to the default soft delete |
| ES-EventType | Instructs the server the event type associated to a posted body |
| ES-EventId | Instructs the server the event id associated to a posted body |