Hierarchical Event Descriptors (HED) Specification

This resource defines the Hierarchical Event Descriptor (HED) specification, including the core specification with detailed rules about the handling of the vocabulary, tool behavior, and errors. 

This specification lays out the rules that HED-compliant tools must follow to correctly handle HED annotations. It is meant for tool developers and for users who need to understand the details of the behavior. If you are new to HED, please visit the HED homepage or the HED resources site. 

 The current, officially released specification can also be browsed in HTML format.

The HED specification is maintained in the GitHub hed-specification repository which is part of the GitHub HED Standard organization. HED is the annotation standard for events and other tabular metadata in the Brain Imaging Data Structure (BIDS) standard.