A duplicate message is the second and every further message with the same text sent to the same number. It rarely happens on purpose — more often it comes from repeating an API call after a timeout, from a double click on a button, or from one number ending up in the recipient list several times. BulkGate protects you against it, but the [transactional and promotional routes](https://www.bulkgate.com/en/helpdesk/general-information/difference-promotional-transactional-sms/) handle it differently.

## How the two protections differ

|                    | Transactional message                        | Promotional message                     |
|:-------------------|:----------------------------------------------|:------------------------------------------|
| What it watches    | the same message repeated over time          | duplicate recipients within one list    |
| Reach              | across requests, a 5-minute window           | only within a single request            |
| Default state      | off                                           | off                                      |
| What you will see  | the message fails with `duplicity_message`   | the recipient quietly drops off the list|

## Transactional messages: the same message repeated over time

You turn it on with the `duplicates_check` parameter in the [transactional](https://www.bulkgate.com/en/docs/advanced-api/advanced-transactional/2.0/) or [simple transactional](https://www.bulkgate.com/en/docs/simple-api/simple-transactional/) API. It accepts `on` and `off` (it also understands `true`/`false`, `1`/`0`, `yes`/`no`), and the default is `off`.

When it is on, BulkGate remembers this combination for every message sent:

| Part of the fingerprint | Note                                                                          |
|:------------------------|:--------------------------------------------------------------------------------|
| Account                 | applies across every application (`application_id`) under one wallet          |
| Channel                 | the same text over SMS and over Viber are two different messages              |
| Phone number            | in international format                                                        |
| Message text            | must match character by character — a different name, time or code makes it a different message |

If a message with the same fingerprint arrives within five minutes, BulkGate discards it and it never reaches the operator.

> [!IMPORTANT]
> The five-minute window starts with the **first** message and discarded attempts do not extend it. Once it expires, the same message goes through again.

For a cascade message, the fingerprint uses the main cascade text, not the texts of the individual channels.

### What you will see in the response

- **A single message** — the API returns a `duplicity_message` error with code `400`. See the list of [error types](https://www.bulkgate.com/en/docs/api-administration-tokens/api-error-types/).
- **A bulk transactional message** — the discarded message gets the `duplicity_message` status and counts towards `total.status.duplicity_message`. The rest of the batch is sent as usual.

> [!CAUTION]
> Think twice before using the protection for one-time passwords. If the code changes with every attempt, it never applies. If you send a fixed text, you will discard the second send within five minutes — and the user who pressed “Resend” gets no message at all.

## Promotional messages: duplicate recipients within one batch

On the promotional route nothing is remembered between requests. BulkGate simply goes through the recipient list built from a single request before sending and keeps the first occurrence. The `duplicates_check` parameter in the [promotional](https://www.bulkgate.com/en/docs/advanced-api/advanced-promotional/2.0/) or [simple promotional](https://www.bulkgate.com/en/docs/simple-api/simple-promotional/) API has three values:

| Value         | What it removes                                            |
|:--------------|:-------------------------------------------------------------|
| `same_text`   | the same message repeated to the same number                |
| `same_number` | any further message to the same number, even with a different text |
| not set       | nothing — the list is sent exactly as you submitted it      |

> [!NOTE]
> The removal is silent — the response carries no status and no duplicate counter. The only trace is a lower recipient count than the number you submitted. If nobody is left after the removal, the request fails with `no_recipients`.

Two consecutive requests do not see each other. Send the same recipient in two batches and both messages go out.

## Campaigns in the portal

A [campaign](https://www.bulkgate.com/en/helpdesk/campaign/campaigns/) goes the promotional route and runs the duplicate check on its own — once the recipient list is built, it shows you how many it found under the **Duplicate message warning** heading:

- **Same number and same text** — the campaign always removes these, with no choice offered.
- **Same number, different text** — this one is up to you. Tick **Remove duplicate recipients** and each number gets a single message; leave it unticked and all of them go out.

In an A/B tested campaign duplicate recipients are always removed, otherwise one person would receive several tested variants and the test result would be worthless.

## What to watch out for

- **The same parameter means two different things.** On the transactional route `duplicates_check` is a switch that protects across requests over time; on the promotional route it selects a method and applies only within one request.
- **A shared account means a shared window.** Several integrations under one wallet can discard each other's messages if they send the same texts to the same numbers.
- **A discarded message is not sent**, so it is neither delivered nor recorded among sent messages.
- **Check the counts in the response.** The promotional route reports no removals — if you compare deliveries against your input list, expect the difference.