Amazon EventBridge events - Amazon EventBridge

Amazon EventBridge events

An event indicates a change in an environment such as an AWS environment, a SaaS partner service or application, or one of your applications or services. The following are examples of events:

  • Amazon EC2 generates an event when the state of an instance changes from pending to running.

  • Amazon EC2 Auto Scaling generates events when it launches or terminates instances.

  • AWS CloudTrail publishes events when you make API calls.

You can also set up scheduled events that are generated on a periodic basis.

For a list of services that generate events, including sample events from each service, see Events from AWS services.

Events are represented as JSON objects and they all have a similar structure, and the same top-level fields.

The contents of the detail top-level field are different depending on which service generated the event and what the event is. The combination of the source and detail-type fields serves to identify the fields and values found in the detail field. For examples of events generated by AWS services, see Events from AWS services.

The following fields appear in an event:


By default, this is set to 0 (zero) in all events.


A Version 4 UUID that's generated for every event. You can use id to trace events as they move through rules to targets.


Identifies, in combination with the source field, the fields and values that appear in the detail field.

Events that are delivered by CloudTrail have AWS API Call via CloudTrail as the value for detail-type.


Identifies the service that generated the event. All events that come from AWS services begin with "aws." Customer-generated events can have any value here, as long as it doesn't begin with "aws." We recommend the use of Java package-name style reverse domain-name strings.

To find the correct value for source for an AWS service, see The condition keys table, select a service from the list, and look for the service prefix. For example, the source value for Amazon CloudFront is aws.cloudfront.


The 12-digit number identifying an AWS account.


The event timestamp, which can be specified by the service originating the event. If the event spans a time interval, the service can report the start time, so this value might be before the time the event is received.


Identifies the AWS Region where the event originated.


A JSON array that contains ARNs that identify resources that are involved in the event. The service generating the event determines whether to include these ARNs. For example, Amazon EC2 instance state-changes include Amazon EC2 instance ARNs, Auto Scaling events include ARNs for both instances and Auto Scaling groups, but API calls with AWS CloudTrail do not include resource ARNs.


A JSON object that contains information about the event. The service generating the event determines thecontent of this field. The detail content can be as simple as two fields. AWS API call events have detail objects with approximately 50 fields nested several levels deep.

The following event in Amazon EventBridge indicates an Amazon EC2 instance being terminated.

{ "version": "0", "id": "6a7e8feb-b491-4cf7-a9f1-bf3703467718", "detail-type": "EC2 Instance State-change Notification", "source": "aws.ec2", "account": "111122223333", "time": "2017-12-22T18:43:48Z", "region": "us-west-1", "resources": [ "arn:aws:ec2:us-west-1:123456789012:instance/i-1234567890abcdef0" ], "detail": { "instance-id": " i-1234567890abcdef0", "state": "terminated" } }