# Check CRM overlap

> POST /v1/connections/{id}/overlap. The New to you check before an order: read-only, email-only, salted SHA-256 matching in memory, nothing retained and nothing added to our database.

Source: https://emailmovers.com/mydatahub/docs/reference/rest/check-connection-overlap

`POST /v1/connections/{id}/overlap`

The New to you check before an order: read-only, email-only, salted SHA-256 matching in memory, nothing retained and nothing added to our database. Matched records are never charged.

| Property | Value |
| --- | --- |
| Endpoint | `POST https://mydatahub.emailmovers.com/v1/connections/{id}/overlap` |
| Operation id | `checkConnectionOverlap` |
| Cost | Free (0 credits) |
| Access | An API key or an OAuth 2.1 token with the scope `pushes:write`. |
| Tag | CRM push |

> **Not yet live.** MyDataHub v2 is built and tested locally and is not yet live. The v2 hosts open at launch, date to confirm. This page describes the contract the API is tested against.

## Request

### Parameters

| Name | In | Type | Required | Description |
| --- | --- | --- | --- | --- |
| `id` | path | string | yes | Format: a CRM connection id: conn_ followed by a 26 character ULID in upper case Crockford base32, such as conn_01JB3Y2X6Y7Z8A1B2C3D4E5F6G. |
| `MyDataHub-Version` | header | string | no | The dated API version, pinned per key when left out. Non-breaking changes ship as new dates; the path major changes only for breaking changes, with a 12 month deprecation window. |

### Body

| Member | Type | Required | Description |
| --- | --- | --- | --- |
| `count_id` | string | no | A count id from POST /v1/counts or count_audience. Either case is accepted; responses use upper case. |
| `quote_id` | string | no | Format: a quote id: qte_ followed by a 26 character ULID in upper case Crockford base32, such as qte_01JB4M2R6T1Y5W8ZAK8Q2V7XN3. |

## Example request

```bash
curl -X POST "https://mydatahub.emailmovers.com/v1/connections/conn_01JB3Y2X6Y7Z8A1B2C3D4E5F6G/overlap" \
  -H "Authorization: Bearer $MYDATAHUB_API_KEY" \
  -H "Content-Type: application/json" \
  --data '{
  "count_id": "cnt_7K2PQ4MAXN3R6TBY5WDZ"
}'
```

## Responses

### 200: The overlap.

Headers: `RateLimit`, `RateLimit-Policy`.

| Member | Type | Always present | Description |
| --- | --- | --- | --- |
| `connection_id` | string | yes | Format: a CRM connection id: conn_ followed by a 26 character ULID in upper case Crockford base32, such as conn_01JB3Y2X6Y7Z8A1B2C3D4E5F6G. |
| `count_id` | string | yes | Format: a count id: cnt_ followed by 20 base32 characters (A to Z and 2 to 7), such as cnt_7K2PQ4MAXN3R6TBY5WDZ. |
| `records` | integer (0 or more) | yes |  |
| `already_held` | integer (0 or more) | yes | Records already in the CRM; never charged. |
| `new_to_you` | integer (0 or more) | yes |  |
| `method` | `salted_sha256_in_memory` | yes |  |
| `retained` | `false` | yes | Nothing from the CRM is kept after the check. |
| `checked_at` | string (date-time) | yes |  |

#### Example response

```json
{
  "connection_id": "conn_01JB3Y2X6Y7Z8A1B2C3D4E5F6G",
  "count_id": "cnt_7K2PQ4MAXN3R6TBY5WDZ",
  "records": 4650,
  "already_held": 548,
  "new_to_you": 4102,
  "method": "salted_sha256_in_memory",
  "retained": false,
  "checked_at": "2026-09-26T10:12:00Z"
}
```

## Errors

Every error is a problem object with a `code` and a `next_step`. Every response carries the `RateLimit` and `RateLimit-Policy` headers; see [Rate limits](https://emailmovers.com/mydatahub/docs/rate-limits.md).

| Status | Problem codes | When |
| --- | --- | --- |
| 400 | [`invalid-request`](https://emailmovers.com/mydatahub/docs/errors/invalid-request.md), [`idempotency-key-required`](https://emailmovers.com/mydatahub/docs/errors/idempotency-key-required.md), [`unsupported-version`](https://emailmovers.com/mydatahub/docs/errors/unsupported-version.md) | The request could not be read, or an Idempotency-Key is missing. |
| 401 | [`authentication-required`](https://emailmovers.com/mydatahub/docs/errors/authentication-required.md), [`account-required`](https://emailmovers.com/mydatahub/docs/errors/account-required.md) | Sign in (OAuth) or send an API key (authentication-required), or create a free account for what the anonymous tier does not cover (account-required). |
| 403 | [`insufficient-scope`](https://emailmovers.com/mydatahub/docs/errors/insufficient-scope.md), [`confirmation-required`](https://emailmovers.com/mydatahub/docs/errors/confirmation-required.md), [`business-details-required`](https://emailmovers.com/mydatahub/docs/errors/business-details-required.md), [`licence-acceptance-required`](https://emailmovers.com/mydatahub/docs/errors/licence-acceptance-required.md), [`dpa-acceptance-required`](https://emailmovers.com/mydatahub/docs/errors/dpa-acceptance-required.md), [`agent-budget-exceeded`](https://emailmovers.com/mydatahub/docs/errors/agent-budget-exceeded.md) | The token lacks a scope (insufficient-scope, with required_scope and a WWW-Authenticate step-up challenge); no person confirmed the spend and no agent key covers it (confirmation-required, with an approval_url); an agent key's per-order cap or monthly budget does not cover it (agent-budget-exceeded); an account made by self-serve sign-up has not yet confirmed its business name and that it is a UK business, which its first order needs (business-details-required); the order needs the Data Licence and Sharing Agreement accepted at the version in force (licence-acceptance-required); or a suppression upload comes before the organisation has accepted the Article 28 data processing agreement in force (dpa-acceptance-required). Nothing is charged. |
| 404 | [`not-found`](https://emailmovers.com/mydatahub/docs/errors/not-found.md) | No such object for this organisation. |
| 422 | [`validation-failed`](https://emailmovers.com/mydatahub/docs/errors/validation-failed.md), [`quote-required`](https://emailmovers.com/mydatahub/docs/errors/quote-required.md), [`dataset-unavailable`](https://emailmovers.com/mydatahub/docs/errors/dataset-unavailable.md) | The request is not valid. errors lists every problem with a JSON pointer and did_you_mean. |
| 429 | [`rate-limited`](https://emailmovers.com/mydatahub/docs/errors/rate-limited.md) | Too many requests. Wait for Retry-After. |
| Any other failure | [`internal-error`](https://emailmovers.com/mydatahub/docs/errors/internal-error.md), [`service-unavailable`](https://emailmovers.com/mydatahub/docs/errors/service-unavailable.md), [`tps-screen-expired`](https://emailmovers.com/mydatahub/docs/errors/tps-screen-expired.md) | Something failed on our side (500 internal-error) or the service is briefly unavailable (503 service-unavailable, with Retry-After). Nothing was charged; retry with the same Idempotency-Key. A count, sample, quote or order with telephone in play is also refused with 503 tps-screen-expired, with no Retry-After, while the dataset version's TPS and CTPS screen is more than 28 days old. |