Volley / HAR to sequence diagram

Turn a HAR file into a sequence diagram.

Record a flow in your browser's Network tab, drop the file into Volley, and get a sequence diagram with the request and response bodies on every arrow.

Three steps

1. Open your browser's developer tools, go to the Network tab and run through the flow: sign in, check out, whatever you want to document.
2. Right-click the request list and choose "Save all as HAR" (the wording varies a little by browser).
3. Open the Volley editor and drop the file on it, or choose "Import a HAR" from the editor's Share menu.

Each host becomes a lane. Each request becomes an arrow with its query, form or JSON body as an in: payload, and each response becomes a dashed reply with its body as out:. Scripts, styles, images and fonts are skipped.

What you get

Here is a short recording of a billing job, converted as is. It is plain Volley source, so you can rename lanes, delete noise, add notes and if branches, and keep it in your repo.

title: Billing run, imported from a HAR file
order: Browser, auth.example.com, api.example.com

// Imported from a HAR file recorded 2026-10-15T17:42:00.000Z

Browser -> auth.example.com: POST /oauth2/token
in: Body
```form
grant_type=client_credentials&client_id=billing-worker&client_secret=<redacted>
```

auth.example.com --> Browser: 200 OK
out: JSON
```json
{
  "access_token": "<redacted>",
  "token_type": "Bearer",
  "expires_in": "900",
  "scope": "invoices:read"
}
```

Browser -> api.example.com: GET /invoices?status=open
in: Query
```params
status: open
```

api.example.com --> Browser: 200 OK
out: JSON
```json
[
  {
    "id": "inv_9001",
    "total": 4200,
    "currency": "USD",
    "due_at": "2026-11-01"
  }
]
```

Browser -> api.example.com: POST /invoices/inv_9001/reminders

api.example.com --> Browser: 202 Accepted
out: JSON
```json
{
  "id": "rem_77",
  "status": "queued"
}
```

Secrets stay out

Recordings are full of credentials. Before anything reaches the diagram, Volley redacts authorization and cookie headers, API keys, CSRF tokens, and secret-looking query parameters, form fields and JSON keys. Look at the client_secret and access_token above. Headers are left out unless you ask for them.

Keep it honest

A diagram you generated once will drift. Record the flow again later and use Update from recording on the same diagram: changed payloads and status codes update in one click, and new requests can be added.

From the command line

The Volley CLI does the same conversion: volley har recording.har, with --headers to keep headers, --host <substring> to keep one service and --title to name the diagram. Agents can call it the same way.

Questions