Siren

Cookie Duration and Attribution Windows

How Siren tracks visitors over time, how long the attribution window stays open, and how this interacts with refunds and renewals.

Last updated: April 10, 2026

An attribution window is the amount of time Siren keeps a visitor connected to the collaborator who referred them. If a visitor clicks an affiliate link today and buys a week later, whether the affiliate earns credit depends on whether the attribution window is still open when the purchase happens. Every affiliate platform has some version of this mechanic. Siren’s version is configured per program, and it’s one of the first settings you’ll want to think through when setting up a new program.

This page explains what the window is, how Siren stores the connection between the visitor and the collaborator, how long the window lasts, and what happens when it closes. If you’re coming from Refersion, Commission Junction, Impact, Post Affiliate Pro, or any other tracking platform, the underlying mechanic is the same. Only the settings are named differently.

How Siren stores the attribution

When a visitor clicks a referral link or applies a coupon code, Siren creates an opportunity that represents the visitor session. The opportunity is tied to the collaborator through an engagement, which is the per-program credit claim for that visit. A cookie in the visitor’s browser keeps the connection alive across sessions, so when they come back a day or a week later, Siren can still tell which collaborator they arrived through.

The cookie doesn’t do the attribution on its own. It’s the lookup key that tells Siren which opportunity to load. The opportunity holds the actual connection to the collaborator and the engagement. This split matters because it means the attribution survives even if the visitor clears other cookies, closes the browser, or comes back from a different device (as long as they return through the same browser that holds the Siren cookie).

How long the window lasts

Each program in Siren has an expiration time, measured in days, that controls how long the attribution window stays open for that program. You configure it when you create the program, and you can change it later from the program edit screen. There’s no global default that applies to all programs. Each program sets its own window independently, because different programs usually have different sales cycles.

Practical guidance on common window lengths:

Thirty days is a common starting point for most traditional affiliate programs. It’s long enough to cover the typical consideration period for a consumer purchase, short enough that it doesn’t artificially inflate attribution for purchases the affiliate wasn’t really responsible for.

Seven to fourteen days fits programs that want to reward last-click behavior, where the goal is to credit the referral that actually led to the conversion rather than a click from weeks ago. This is common for impulse-purchase products or for programs where the seller wants attribution to feel current.

Sixty to ninety days fits high-consideration purchases (expensive products, long sales cycles, B2B software trials) where the customer realistically needs time to decide. Pushing the window shorter than the actual consideration period means affiliates stop earning for referrals they legitimately drove.

None of these numbers are prescriptive. Think about how long it typically takes a referred visitor to convert, then pick a window that covers that time with a bit of buffer.

What happens when the window closes

When the window closes, the opportunity expires. Subsequent purchases by the same visitor don’t credit the original collaborator unless a new engagement is recorded. If the visitor clicks the same affiliate’s link again after the window expired, a new opportunity and a new engagement get created, and the clock starts over. But if they just come back directly and buy, the original collaborator earns nothing because the attribution has timed out.

This is intentional and matches how cookie-based attribution works across every affiliate platform. A cookie without an expiration would mean a single click could claim attribution for every purchase that visitor ever makes, which isn’t the incentive structure most programs want.

Interactions with refunds and renewals

Refunds aren’t affected by the attribution window. When a refund happens, the original conversion is reversed regardless of whether the cookie has expired, because the refund is tied to the transaction itself rather than to a live cookie. A customer who buys today, gets attributed to their affiliate, and returns the product in six months will have their conversion reversed through the normal refund pipeline. The affiliate’s original credit goes away because the sale itself was undone, not because the window closed.

Renewals on subscription products work differently. If your store uses subscriptions and you’ve enabled renewal tracking, each renewal fires a new conversion tied to the renewal event. The attribution window behavior then depends on whether the renewal tracking is turned on and whether your integration supports it. See the integration feature matrix for which integrations support renewals.

For SaaS programs with long trial-to-paid windows, the relevant question is whether your attribution window is long enough to span the trial. If a customer signs up for a 30-day free trial through an affiliate link and your attribution window is 14 days, the trial will convert to paid after the window closes and the affiliate will get no credit. For that situation, set the window to match or exceed your trial length plus a buffer. When the subscription programs doc ships at subscription programs, it’ll cover this scenario in more detail.