Connect Polar

No API key needed. You add one webhook endpoint in Polar with the URL from your Checkout Sync settings, then paste the secret Polar makes back into your settings.

1. In your Checkout Sync settings, press Connect a checkout, then Polar, then Connect Polar. You'll see your webhook URL.
2. In Polar, open your organization's Settings → Webhooks and press Add Endpoint.
3. Paste the URL and leave the format on Raw.
4. Tick these events: order.paid, order.refunded, subscription.canceled, subscription.uncanceled, subscription.revoked, subscription.past_due.
5. Save. Polar shows the endpoint's secret (it starts with whsec_). Copy it and paste it into the setup box in your settings, then press Save Polar's secret.

Polar signs webhooks with Standard Webhooks for secrets made since 8 September 2026 (older secrets use Polar's own format). Checkout Sync accepts both. Use the secret Polar generates for you, and paste it back to us.

Good to know

• Renewals arrive as new paid orders. They update the buyer's fields but don't join groups again.
• Polar doesn't send a card-update link with its events. Add your customer portal link (below) and we put it in {$checkout_update_payment_url} and {$checkout_manage_url}; until then those stay empty for Polar buyers.
• A cancellation at the end of the period puts the buyer in Canceled straight away, with the last day in {$checkout_ends_on} and their reason in {$checkout_reason} when they gave one. {$checkout_status} turns to canceled when access really ends.
• Testing with Polar's sandbox? Connect it as a separate checkout and tick This is a Polar sandbox. Sandbox orders then don't count toward your plan.

Your customer portal link

Polar gives every organization a page where buyers sign in by email and manage their subscription and card. Its address is https://polar.sh/your-org/portal, with your organization's short name (the one in your Polar storefront's address) in place of your-org. On Polar's sandbox it's https://sandbox.polar.sh/your-org/portal.

Open it in a private window to check it, then paste it under Your checkouts in your settings, next to Polar, and press Save link.

Import past customers

1. In Polar, open your organization's Settings, then Developers, and make a new organization access token with the orders:read scope.
2. In your Checkout Sync settings, under Import past customers, pick how far back to go, paste the token and press Import.

We use the token only for that import and delete it when the import ends (2 days at most). Imported buyers get their fields filled in and join no groups unless you tick Also put them in my groups. Imports don't count toward your plan. MailerLite's anti-spam policy only lets you email buyers from the last 2 years without other permission, so if you tick the box, keep the range to a year or less ("Everything" is refused with it).