HAR Import

Crankfire can import HTTP Archive (HAR) files and convert them to load test endpoints. This allows you to record browser sessions and replay them as load tests.

What is HAR?

HAR (HTTP Archive) is a JSON-based format for recording HTTP transactions. Most browsers and developer tools can export HAR files:

Quick Start

Basic Usage

crankfire --har recording.har --total 100

This loads all HTTP requests from the HAR file and executes them as a load test.

With Filtering

Filter by host to include only specific domains:

crankfire --har recording.har --har-filter "host:api.example.com" --total 100

Filter by HTTP method:

crankfire --har recording.har --har-filter "method:GET,POST" --total 100

Combine filters with semicolons:

crankfire --har recording.har --har-filter "host:api.example.com;method:POST" --total 100

CLI Flags

Flag Description Example
--har Path to HAR file --har recording.har
--har-filter Filter HAR entries --har-filter "host:api.example.com"

Config File Usage

You can also specify HAR import in a config file:

har_file: ./recording.har
har_filter: "host:api.example.com;method:GET,POST"
concurrency: 10
duration: 1m

Then run:

crankfire --config loadtest.yaml

Filter Format

The --har-filter flag accepts a semicolon-separated list of filters:

Host Filter

Include only requests to specific hosts:

host:api.example.com
host:api.example.com,cdn.example.com

Method Filter

Include only specific HTTP methods:

method:GET
method:GET,POST,PUT

Combined Filters

Combine multiple filters with semicolons:

host:api.example.com;method:POST

Automatic Filtering

Crankfire automatically excludes static assets by default:

This keeps your load test focused on API endpoints rather than static content.

What Gets Imported

From each HAR entry, Crankfire extracts:

HAR Field Endpoint Field Notes
request.method method HTTP method (GET, POST, etc.)
request.url url Full URL including query string
request.headers headers Request headers (hop-by-hop headers filtered)
request.postData.text body Request body for POST/PUT/PATCH
URL path name Endpoint name for metrics

Filtered Headers

The following hop-by-hop headers are automatically removed:

Merging with Config Endpoints

HAR endpoints can be combined with endpoints defined in your config file:

target: https://api.example.com
har_file: ./recording.har

# These endpoints are added to HAR endpoints
endpoints:
  - name: "health-check"
    path: /health
    weight: 1

The HAR endpoints are appended to any existing endpoints, giving you flexibility to mix recorded and manually-defined requests.

Security Warning

⚠️ HAR files may contain sensitive data:

When you load a HAR file, Crankfire displays a warning:

WARNING: HAR file may contain sensitive data (cookies, auth tokens). 
Review endpoints before use in production.

Best Practices:

  1. Review HAR files before using them in load tests
  2. Remove or redact sensitive headers (Authorization, Cookie)
  3. Don’t commit HAR files with real credentials to version control
  4. Consider using Data Feeders for parameterized auth tokens

Workflow Example

Step 1: Record Browser Session

  1. Open browser DevTools (F12)
  2. Go to Network tab
  3. Clear existing entries
  4. Perform the user workflow you want to test
  5. Right-click → “Save all as HAR”

Step 2: Review and Filter

Check what’s in your HAR file:

# Count entries
cat recording.har | jq '.log.entries | length'

# List URLs
cat recording.har | jq '.log.entries[].request.url'

Step 3: Run Load Test

crankfire \
  --har recording.har \
  --har-filter "host:api.example.com" \
  --concurrency 10 \
  --duration 1m \
  --dashboard

Step 4: Generate Report

crankfire \
  --har recording.har \
  --har-filter "host:api.example.com" \
  --concurrency 10 \
  --total 1000 \
  --html-output har-test-report.html

Limitations

Next Steps