> For the complete documentation index, see [llms.txt](https://support.referralhero.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://support.referralhero.com/campaign-builder/unique-identifier.md).

# Unique Identifier

This is a very unique feature of ReferralHero. When you are setting up your campagin, you can select a unique identifier for your subscribers. Here are a few important things to know:

* The unique identifier will be the ID we use to reference and add subscribers to your campagin 
* The unique identifier type cannot be changed after a subscriber has been added to your campaigns
* The unique identifier is a required field in our Widget and APIs
* The unique identifier requirement can only be bypassed when subscribers are created manually on the dashboard

### Selecting a Unique Identifier Type

* [Email](/campaign-builder/unique-identifier/confirmation-email.md)
* [Phone Number](/campaign-builder/unique-identifier/phone-number-verification.md)
* Web3 Wallet Address
* Other (customer ID, social media handle, etc.)

<figure><img src="/files/hL0zGSrfmapmakhptu5t" alt=""><figcaption></figcaption></figure>

### Verifying the Unique Identifier

After selecting a unique identifier, you will want to consider enabling the verification method. Subscriber verification is important for security reasons to ensure only real people are signing up for your campaign. These are your options:

| Verification Options                                                                                  | Verification Behavior                                                                                                                                                                                                      |
| ----------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Require Verification                                                                                  | The subscriber will be considered verified and added to your campaign only when the unique identifier is confirmed.                                                                                                        |
| Require Primary and [Secondary Verification](/campaign-builder/unique-identifier/sms-verification.md) | The subscriber will need to first confirm the primary verification method and then the secondary verification method (the subscriber will be considered verified and added to your campaign only when both are confirmed). |
| Disable Verification                                                                                  | No verification method will be triggered, the subscriber will be added without any verification                                                                                                                            |

If you choose to verify the unique identifier. Please read additional material on your selection:

* Email Verification: [Sending the confirmation email](/campaign-builder/unique-identifier/confirmation-email.md)
* Phone Number Verification: [Sending an SMS message](/campaign-builder/unique-identifier/phone-number-verification.md)
* Crypto Wallet Address Verification: [Connecting crypto wallets](/campaign-builder/integrations/blockchain.md#crypto-wallet-address-verification)&#x20;

#### Phone Number Verification Behavior

When phone number verification is enabled:

* Invalid phone numbers are rejected during signup
* Only valid phone numbers are accepted
* SMS messages are only sent to valid phone numbers

When phone verification is not enabled:

* Invalid phone numbers are accepted
* No SMS messages are triggered for invalid numbers

### Verification Considerations

Each unique identifier has an optional verification process that you can enable. When deciding to enable this feature, consider:

| Verify                                                                                                   | Not Verify                                                                 |
| -------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------- |
| You're running a contest                                                                                 | You're running a referral or affiliate program                             |
| Assurance a valid unique identifier was provided                                                         | You have your process to verify the subscriber                             |
| Protection against [spambots](https://en.wikipedia.org/wiki/Spambot), email scams, and fake subscribers. | Our anti-fraud algorithm will identify potential spam and fake subscribers |
| It is a legal requirement in your country                                                                | This additional step can sometimes restrict referrals                      |
| Archived record documenting the subscriber's consent                                                     | Verification can be enabled at any time during your campagin               |


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