HTTP field: NEL
NEL is a registered field in the IANA HTTP Field Name Registry.
HTTP fields are message metadata; their meaning depends on direction, combination rules, and the HTTP version carrying them. Use NEL only according to its defining specification. Defining reference: Network Error Logging.
Registry-backed field entry. The field is currently marked registered by IANA. Defining reference: Network Error Logging.
Check whether the field is end-to-end or hop-by-hop, whether it varies a cache response, and whether it carries security-sensitive data before forwarding or logging it.
Check the linked specification for its direction, combination rules, caching behavior, and security considerations before generating or trusting it.
IANA registry: http-fields/field-names
Registry reference: Network Error Logging
Sources