# Start a campaign

> Validates the campaign is ready, then flips it to active and sets startedAt (on first start only, later restarts don't reset it). The workspace must not be…

Source: https://warmerly.com/docs/campaigns/start-a-campaign

```text
POST /campaigns/{id}/start
```

Validates the campaign is ready, then flips it to `active` and sets `startedAt` (on first start only, later restarts don't reset it). The workspace must not be billing-locked, and starting a draft, completed or archived campaign must fit your plan's active-campaign limit. It then runs the same checks as [`GET /campaigns/{id}/readiness`](https://warmerly.com/docs/campaigns/start-a-campaign#readiness-check), plus a live check that the AI provider is reachable when the copy uses `{{ai_opener}}`:

- At least one step exists that is a valid email step (`subject` + `bodyText`), a LinkedIn step (`linkedin_connection` / `linkedin_message`).
- Your plan includes the channel(s) the campaign actually uses.
- Your monthly campaign send limit hasn't been reached.
- At least one sending account is attached for each channel the campaign uses (email → [senders](https://warmerly.com/docs/campaigns/start-a-campaign#senders-email), LinkedIn → [linkedin-senders](https://warmerly.com/docs/campaigns/start-a-campaign#linkedin-senders)).
- At least one lead is `queued`.
- Copy checks: every merge tag exists, the campaign brief is written when the copy uses `{{ai_opener}}`, and the copy does not link to a Warmerly domain.

Checks marked `severity: "warning"` do not block, but the start is refused with `400` and `error.details.needsAcknowledgement: true` until you repeat the call with `{ "acknowledgeWarnings": true }` in the JSON body.

```bash
curl -X POST https://app.warmerly.com/api/v1/campaigns/b6a1e7b0-2f2b-4b7a-8e2a-1a2b3c4d5e6f/start \
  -H "X-Api-Key: wmv_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
```

```json
{ "campaign": { "id": "b6a1e7b0-2f2b-4b7a-8e2a-1a2b3c4d5e6f", "status": "active", "startedAt": "2026-07-02T10:00:00.000Z", "...": "..." } }
```

Failing a readiness check returns `400 bad_request` with a human-readable `message` (e.g. `"Add at least one sending mailbox"`) and the checks in `error.details.checks`. Missing plan access returns `403 channel_not_included`; hitting the monthly send cap returns `402 payment_required`. Hitting your plan's active-campaign limit returns `402 plan_capacity`, a billing-locked workspace returns `402 billing_locked`, and a campaign whose only senders are not allowed to send campaigns at all (for example a free mailbox while sending from free mailboxes is switched off) returns `409` with code `sender_cannot_send_campaigns`.

## More from Campaigns

- [Delete a campaign](https://warmerly.com/docs/campaigns/delete-a-campaign): Deletes the campaign and cascades to its steps, senders, leads, and send history. This cannot be undone.
- [Pause a campaign](https://warmerly.com/docs/campaigns/pause-a-campaign): Sets an active campaign's status to paused (pausing one that is already paused is a no-op; any other status…
- [Resume a campaign](https://warmerly.com/docs/campaigns/resume-a-campaign): Sets a paused campaign back to active; any other status returns 409 conflict (use start instead). Re-checks…