Result Listeners & JTL Files

Running Tests in CLI Mode

The recommended way of executing a load test is using JMeter command-line non-GUI mode:

jmeter -n -t test-plan.jmx -l results/test-result.jtl

Example: Full Command with Report Generation

jmeter -n \
  -t my-test-plan.jmx \
  -f \
  -l test-result.jtl \
  -e -o results/dashboard/

The command kicks off the test, writes results into .jtl file, and generates HTML Reporting Dashboard under results/dashboard/ folder.

Passing Parameters

Override JMeter properties from the command line:

jmeter -n -t test.jmx -l results.jtl \
  -Jhost=api.staging.example.com \
  -Jthreads=200 \
  -Jduration=600

Understanding the .jtl Test Results File

The .jtl (JMeter Test Log) is a CSV (by default) or XML file that captures Sample Results and writes them each on the separate row:

timeStamp,elapsed,label,responseCode,responseMessage,threadName,dataType,success,failureMessage,bytes,sentBytes,grpThreads,allThreads,URL,Latency,IdleTime,Connect
1712234567890,245,GET /posts/1,200,OK,Thread Group 1-1,text,true,,1234,456,10,10,https://demoblaze.com/1,120,0,45

Key Columns

Analyzing .jtl Files in the GUI

You can load a .jtl file into any listener after the test:

1. Open JMeter GUI.
2. Add a listener (e.g., Aggregate Report).
3. Click the Browse button in the Filename field and select your .jtl file.

The listener will populate with the calculated data.

Analyzing .jtl Files with JMeter Plugins Command-Line Tool

For quick analysis without opening the GUI:

Using JMeterPluginsCMD Command Line Tool (via JMeter Plugins)

If you installed the Plugins Manager, the JMeterPluginsCMD tool can generate reports from .jtl files in CSV and/or PNG formats:

./JMeterPluginsCMD.sh --generate-csv AggregateReport.csv --input-jtl test-result.jtl --plugin-type AggregateReport

This command will produce CSV version of what is shown in the Aggregate Report listener. It can be used for quick analysis and different test runs comparison.

Configuring What Gets Saved

You can control which fields are written to the .jtl file via user.properties:

# Save response headers and body (useful for debugging, large file size)
jmeter.save.saveservice.response_data=false
jmeter.save.saveservice.response_headers=false
jmeter.save.saveservice.request_headers=true
jmeter.save.saveservice.samplerData=false

# Save assertion results
jmeter.save.saveservice.assertions=true
jmeter.save.saveservice.assertion_results_failure_message=true

# CSV format (default and recommended)
jmeter.save.saveservice.output_format=csv

Full description of parameters is available in Results file configuration chapter of JMeter User Manual.

Tip: For production load tests, keep the defaults (CSV, no response data). Only enable response body saving for debugging runs with few threads, or use a dedicated Listener for this.

Finally, let’s see how to generate HTML reports for your performance tests.