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You can output granular data points in JSON format. To do so, use k6 run with the --out flag. Pass the path for your JSON file as the flag argument:

$ k6 run --out json=test_results.json script.js

Or if you want to get the result gzipped, like this:

$ k6 run --out json=test_results.gz script.js

To inspect the output in real time, you can use a command like tail -f on the file you save:

$ tail -f test_results.json

JSON format

The JSON output has lines as follows:

{"type":"Point","data":{"time":"2017-05-09T14:34:45.239531499+02:00","value":459.865729,"tags":{"group":"::my group::json","method":"GET","status":"200","url":""}},"metric":"http_req_duration"}

Each line either has information about a metric, or logs a data point (sample) for a metric. Lines consist of three items:

  • type - can have the values Metric or Point where Metric means the line is declaring a metric, and Point is an actual data point (sample) for a metric.
  • data - is a dictionary that contains lots of stuff, varying depending on the "type" above.
  • metric - the name of the metric.


This line has metadata about a metric. Here, "data" contains the following:

  • "type" - the metric type ("gauge", "rate", "counter" or "trend")
  • "contains" - information on the type of data collected (can e.g. be "time" for timing metrics)
  • "tainted" - has this metric caused a threshold to fail?
  • "threshold" - are there any thresholds attached to this metric?
  • "submetrics" - any derived metrics created as a result of adding a threshold using tags.


This line has actual data samples. Here, "data" contains these fields:

  • "time" - timestamp when the sample was collected
  • "value" - the actual data sample; time values are in milliseconds
  • "tags" - dictionary with tagname-tagvalue pairs that can be used when filtering results data

Processing JSON output

You can use jq to process the k6 JSON output.

You can quickly create filters to return a particular metric of the JSON file:

$ jq '. | select(.type=="Point" and .metric == "http_req_duration" and .data.tags.status >= "200")' myscript-output.json

And calculate an aggregated value of any metric:

$ jq '. | select(.type=="Point" and .metric == "http_req_duration" and .data.tags.status >= "200") | .data.value' myscript-output.json | jq -s 'add/length'
$ jq '. | select(.type=="Point" and .metric == "http_req_duration" and .data.tags.status >= "200") | .data.value' myscript-output.json | jq -s min
$ jq '. | select(.type=="Point" and .metric == "http_req_duration" and .data.tags.status >= "200") | .data.value' myscript-output.json | jq -s max

For more advanced cases, check out the jq Manual

Summary export

If you want to see only the aggregated data, you can export the end-of-test summary to a JSON file. For more details, refer to the handleSummary() topic in the end-of-test summary docs.

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