> ## Documentation Index > Fetch the complete documentation index at: https://docs.aftersell.com/llms.txt > Use this file to discover all available pages before exploring further. # Subscription upgrades integrations A Subscription Upgrade never changes a subscription inside Aftersell alone. The actual change — a new frequency, a swapped product, or a recurring discount — is applied inside the subscription platform that powers your store's subscriptions. The connection between Aftersell and that platform is the **integration**. ## Why an integration is required When a customer accepts an upgrade, two things happen in parallel: * **In Shopify**, Aftersell adds the offer product (a placeholder line item) to the order. * **In your subscription platform**, Aftersell calls the provider's API to modify the customer's existing subscription. That second step only works if Aftersell is connected to your provider with a valid API token that holds the right permissions. This is why [Step 1 of the setup wizard](/aftersell/subscription-upgrades-setup#step-1-connect-provider) asks you to pick a provider and paste an API token before you can build the offer. Without a working integration, the offer product would be added to the order but no subscription would change. ## Supported platforms Subscription Upgrades is currently compatible with three platforms. Each has its own token scopes, capabilities, and quirks, so follow the dedicated guide for the platform you use. All upgrade types. Prepaid and postpaid. Near real-time sync. All upgrade types. Prepaid and postpaid. Near real-time sync. All upgrade types. Postpaid only. Up to 24-hour sync delay. ## If you use a different subscription app If you use a subscription app other than Recharge, Skio, or Loop, you cannot use Subscription Upgrades at this time. That means you cannot offer an upsell that modifies a customer's existing subscription, whether that is changing the delivery or billing frequency, swapping to a different subscription product, or both. You can, however, still use other post-purchase offer types: * [Subscription Upsell](/aftersell/subscriptions_in_post_purchase_offers), to add a new subscription line item to a one-time order. * [Replacement Upsell](/aftersell/replacement_upsells), to swap a one-time product in the order for another product. This covers one-time to one-time (including the same product in a different quantity or variant) and one-time to subscription (the customer's order becomes a subscription order instead of a one-time order). Replacement Upsell cannot operate on a subscription line item in the order. If the original purchase was a subscription, use Subscription Upgrade instead. ## Related * [Overview](/aftersell/subscription-upgrades) — how Subscription Upgrades work end to end. * [Setup & configuration](/aftersell/subscription-upgrades-setup) — connect your provider and build the offer.