URL: /code/apps/analytics-and-experiments/capture · Id: `page:/code/apps/analytics-and-experiments/capture`

# Event.capture

> Records one Event from your Site or product, such as a signup, so every number above can read it.

POST https://api.sb/{your-domain}/events/capture

Records one [Event](https://startupbuilder.dev/business/nouns/event) from your [Site](https://startupbuilder.dev/business/nouns/site) or product, such as a signup, so every number above can read it.

- **Action class:** None
- **Approval:** Runs on its own
- **Emits:** `Event.captured`
- **Price:** Free

```text title="Run it · Ask"
Record that a visitor downloaded the rent-ledger template.
```

```ts title="Run it · SDK"
import { $ } from 'startup-builder'

const result = await $.try.Event.capture({ name: 'Template.downloaded', data: { page: '/rent-ledger-template' }, visitor: 'https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j' })
```

```json title="Run it · Response"
{
  "api": "https://api.sb/leaseline.app",
  "event": {
    "$id": "https://api.sb/leaseline.app/events/event_Td7dL2wN4a",
    "$type": "Event",
    "name": "Template.downloaded"
  },
  "action": {
    "operation": "Event.capture",
    "mode": "try",
    "status": "done"
  }
}
```

Its Inputs, Outputs, Effects and guards quote [the hub’s `Event.capture`](https://startupbuilder.dev/business/nouns/event/capture); this page adds what each Venue honors, its limits and a worked call. It is one of the [Verbs](https://startupbuilder.dev/business/nouns/verb) of [Analytics and experiments](/code/apps/analytics-and-experiments#verbs).

## Inputs
| Name | Type | Meaning |
| --- | --- | --- |
| `name` | `string` | Required. The Event name, a Noun and a past-tense Verb, such as `Lead.created`. |
| `data` | `json` | The Event’s properties. Optional. |
| `visitor` | `Visitor` | The Visitor it happened to, when the person is not known. Optional. |

## Outputs
| Field | Type | What `null` means |
| --- | --- | --- |
| `event` | `Event` | Never null: the captured Event. |

## Effects
**Action class**

None: no approval rule names it, so it runs within its seat’s Permissions and Limits

**Modes**

- `try`: Runs every check and returns the record as it would be; nothing is stored.
- `send`: Returns a pending Action at once; `Event.captured` fires when it is done.
- `do`: Waits for the Action to finish and returns the record.

**Idempotency**

Only with a key: the same `Idempotency-Key` and input return the first Action, and the same key with other input returns `409`.

**Saved or shared**

Every Verb emits its own Event, so the registry is the tracking plan.

**Emits**

`Event.captured` with `{ event }`

**Performed by**

[Analyst](https://startupbuilder.dev/agents/marketing/analyst)

**Price**

Free on your own account: the platform charges nothing for the call.

## On each Venue
It acts on your own records and reaches no Venue, so every account answers the same way.

## What try does
Runs every check the call meets and returns the record as it would be; nothing is stored, sent or posted.

## Refuses when
The hub sets no guard of its own on this call: it refuses only on the shared checks every write meets (a missing record, a Permission the seat lacks).

## When it waits
Returns in one response; nothing waits.

## Example
In `send` mode the call returns its pending Action at once, and `Event.captured` delivers the result.

**Ask**

```text
Record that a visitor downloaded the rent-ledger template.
```

**API**

```bash
curl -X POST "https://api.sb/leaseline.app/events/capture?mode=send" \
  -H "Authorization: Bearer $SB_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
  "name": "Template.downloaded",
  "data": {
    "page": "/rent-ledger-template"
  },
  "visitor": "https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j"
}'
```

**CLI**

```bash
npx startup-builder do Event.capture --send --data '{
  "name": "Template.downloaded",
  "data": {
    "page": "/rent-ledger-template"
  },
  "visitor": "https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j"
}'
```

`--send` returns the pending Action at once.

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "mode": "send",
    "code": "return await $.Event.capture({ name: 'Template.downloaded', data: { page: '/rent-ledger-template' }, visitor: 'https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j' })"
  }
}
```

**SDK**

```ts
import { $ } from 'startup-builder'

const result = await $.send.Event.capture({
  name: 'Template.downloaded',
  data: { page: '/rent-ledger-template' },
  visitor: 'https://api.sb/leaseline.app/visitors/visitor_Xs4dF8gH2j',
})
```


```json title="Response, in send mode"
{
  "mode": "send",
  "action": {
    "$id": "https://api.sb/leaseline.app/actions/action_Sd3kQ9vT2w",
    "operation": "Event.capture",
    "status": "pending",
    "reason": "running"
  }
}
```

To retry, send the same `Idempotency-Key`: the retry returns the first answer for $0. A new key reads again.

## Used by
- **Workflows:** [Ad test setup](/capabilities/run-ads/ad-test-setup)
- **Jobs:** [Keep and grow customers](/capabilities/keep-and-grow)

## Related
[`Metric.query`](/code/apps/analytics-and-experiments/query) · [`Metric.watch`](/code/apps/analytics-and-experiments/watch) · [`Experiment.start`](/code/apps/analytics-and-experiments/start) · [`Experiment.conclude`](/code/apps/analytics-and-experiments/conclude) · [`Dashboard.ask`](/code/apps/analytics-and-experiments/ask) · [`Metric.define`](/code/apps/analytics-and-experiments/define) · [`Hypothesis.test`](/code/apps/analytics-and-experiments/test) · [`Dashboard.schedule`](/code/apps/analytics-and-experiments/schedule)