hubcap har - Capture network activity in HAR format

When to use

Capture network activity in standard HTTP Archive (HAR) format for analysis, replay, or import into tools like Chrome DevTools. Use network for real-time NDJSON streaming instead.

Usage

hubcap har [--duration <duration>]

Arguments

None.

Flags

Flag	Type	Default	Description
`--duration`	duration	`5s`	How long to capture

Output

A single HAR format JSON object written to stdout conforming to the HTTP Archive 1.2 specification.

{
  "log": {
    "version": "1.2",
    "creator": {
      "name": "hubcap",
      "version": "1.0.0"
    },
    "entries": [
      {
        "startedDateTime": "2025-01-15T10:00:00.000Z",
        "request": {
          "method": "GET",
          "url": "https://example.com/api/data",
          "headers": []
        },
        "response": {
          "status": 200,
          "statusText": "OK",
          "headers": [],
          "content": {
            "size": 1234,
            "mimeType": "application/json"
          }
        },
        "time": 150
      }
    ]
  }
}

Errors

Condition	Exit code	Stderr
Chrome not connected	2	`error: connecting to Chrome: ...`
Duration parse failure	1	`error: invalid duration "<value>"`
Timeout exceeded	3	`error: timeout`

Examples

Capture 5 seconds of network activity (default duration):

hubcap har

Capture 30 seconds and save to a file:

hubcap har --duration 30s > trace.har

Capture and count the number of requests:

hubcap har --duration 10s | jq '.log.entries | length'

Navigate to a page and capture the resulting network activity:

hubcap goto "https://example.com" && hubcap har --duration 10s > page-load.har