> ## Documentation Index
> Fetch the complete documentation index at: https://developers.referralful.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Attribution methods

> How Referralful credits the right affiliate, including setups where the marketing site and app are on different domains.

Referralful credits an affiliate using whichever signal it can find at the time of the sale.
Pick the method that matches how your site and billing are set up.

## Quick guide

| Method                     | Needs the snippet?      | Works across separate domains?                   |
| -------------------------- | ----------------------- | ------------------------------------------------ |
| **Referral link (cookie)** | Yes                     | Same registrable domain only (apex + subdomains) |
| **Pass the referral id**   | Capture only            | Yes — any domains                                |
| **Coupon code**            | No                      | Yes — any domains                                |
| **Customer email**         | Yes (to track the lead) | Same registrable domain only                     |

## 1. Referral link (cookie) — the default

A visitor lands on `yourbrand.com/?via=token`. The snippet stores the referral in a cookie on
your **registrable domain** (`.yourbrand.com`), so it is shared across the apex and every
subdomain automatically — `yourbrand.com`, `www.yourbrand.com`, and `app.yourbrand.com` all
see it. Each page that starts checkout needs the snippet loaded so `window.AffID.referral` is
available.

<Note>
  The cookie is shared across **subdomains of one registrable domain**. If your marketing site
  and app are on **completely different domains** (e.g. `brand-marketing.com` and `brandapp.io`),
  the cookie cannot bridge them — use method 2 or 3 below.
</Note>

## 2. Pass the referral id (separate domains)

Capture `window.AffID.referral` on the landing page, carry it with the user (store it on their
account, or pass it through your signup URL), and send it as `referral_id` when they pay:

```bash theme={null}
curl https://api.referralful.com/v1/conversions \
  -u rfl_live_your_secret: \
  -H "Content-Type: application/json" \
  -d '{ "referral_id": "ref_abc123", "amount_cents": 4900, "external_id": "invoice_12345" }'
```

This works no matter how many domains are involved, because you carry the id yourself.

## 3. Coupon codes (cookieless)

Give each affiliate a promo code. When a customer uses it, the sale is attributed by the code —
no link, no cookie, no snippet required. This is the most robust option for fully separate
domains or sites you can't add JavaScript to.

Assign a code to an affiliate:

```bash theme={null}
curl https://api.referralful.com/v1/affiliate_coupons \
  -u rfl_live_your_secret: \
  -H "Content-Type: application/json" \
  -d '{ "affiliate_id": "aff_123", "token": "ALEX20" }'
```

Then:

* **Stripe** — when the customer applies the coupon (or promotion code) at Checkout, Referralful
  reads it from the webhook and credits the affiliate automatically.
* **Any other billing** — pass the code as `coupon` when reporting the sale:

  ```bash theme={null}
  curl https://api.referralful.com/v1/conversions \
    -u rfl_live_your_secret: \
    -d '{ "coupon": "ALEX20", "amount_cents": 4900, "external_id": "invoice_12345" }'
  ```

## 4. Customer email

If the visitor was tracked as a lead (snippet on the marketing site) and later pays, Referralful
can match the sale by the customer's email. Pass `email` to `/v1/conversions`, or it resolves
automatically for Stripe. This needs the lead to have been tracked first, so it shares the
same-domain limitation as the cookie.