Each event has some metadata attached to it on ingestion; all events will have an @id, @timestamp, @timezone, and @rawstring field. From Humio version 1.15 there is also a @ingesttimestamp that holds the time when the event ingested. From Humio version 1.17 there is also a @timestamp.nanos for extended precision of timestamp below millisecond.

Notice that all metadata fields start with @ to make them easy to identify.

The two most important are @timestamp and @rawstring and will be described in detail below.

Tag fields define how events are physically stored and indexed. They are also used for speeding up queries.

Users can associate custom tags as part of the parsing and ingestion process but their use is usually very limited. The only built-in tags are #repo and #type and both are described in detail below.

Usually the client sending data to Humio will be configured to include #host and #source tags that contain the hostname and file that the event was read from.

Any field that is not a tag or metadata is a user field. They are extracted at ingest by a parser or at query time by a regular expression. User fields are usually the interesting part of an event, containing application specific information.

Humio represents the original text of the event in the @rawstring attribute.

One of the greatest strengths of Humio is that it keeps the original data and nothing is thrown away at ingest. This allows you to do free-text searching across all logs and to extract virtual fields at query time for parts of the data you did not even know would be important.

You can read more about free-text search and extracting fields in the search documentation.

The timestamp of an event is represented in the @timestamp field. This field defines where the event is stored in Humio's database and is what defines whether an event is included in search results when searching a time range.

The timestamp needs special treatment when parsing incoming data during ingestion.

The timestamp of when an event was ingested is represented in the @ingesttimestamp field. The value is milliseconds-since-epoch. Searches can restrict the data they search using this timestamp. Currently this can be done by including @ingesttimestamp > X AND @ingesttimestamp < Y early in the search pipeline, where X and Y are the bounds as milliseconds since 1/1/1970. Future versions of Humio will allow selecting these numbers using the time selector in the UI as well.

All events have a special #repo tag that denotes the repository that the event is stored in. This is useful in cross-repository searches when using views.

The type field is the name of the parser used to ingest the data.