> For the complete documentation index, see [llms.txt](https://emotiv.gitbook.io/cortex-api/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://emotiv.gitbook.io/cortex-api/markers.md).

# Markers

A marker is to mark a point in time, or a period of time, inside a [record](/cortex-api/records.md).

Markers are always linked to a record, so you must start a record before you add a marker. You can't add nor update a marker after the record is stopped. You can associate some data to each marker, like a value and a label.

There are two types of markers:

* An instance marker is to mark a point in time. You call [injectMarker](/cortex-api/markers/injectmarker.md) to create the marker at a specific timestamp.
* An interval marker is to mark a period of time, with a beginning and an end. First you create an instance marker with [injectMarker](/cortex-api/markers/injectmarker.md). This sets the beginning of the interval. Then you call [updateMarker](/cortex-api/markers/updatemarker.md) to set the end of the interval, turning the instance marker into an interval marker.