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Polar Webhooks

How to Test Polar Webhooks Locally (2026)

Polar (polar.sh) sends webhooks for order, subscription, checkout, and benefit events. Polar follows the Standard Webhooks specification — each delivery carries webhook-id, webhook-timestamp, and webhook-signature headers, with an HMAC-SHA256 signature you verify using your endpoint secret.

With HookSense, point Polar at a callback endpoint and let an AI agent await the result over MCP: create_callback_endpoint → wait_for_callback → verify_signature. Run npx @hooksense/mcp in Claude Desktop, Cursor, or any MCP client. No polling.

Signature Header

webhook-signature

Algorithm

HMAC-SHA256 (Standard Webhooks spec)

Setup Guide

  1. 1Create a free HookSense endpoint at hooksense.com
  2. 2Copy your unique webhook URL
  3. 3In Polar → Settings → Webhooks → Add Endpoint
  4. 4Paste your HookSense URL and copy the generated endpoint secret
  5. 5Add the secret to HookSense to verify the webhook-signature header
  6. 6Select the events you want and save
  7. 7Trigger a test order or checkout to see it land in HookSense

Common Polar Webhook Events

checkout.created
checkout.updated
order.created
order.paid
subscription.created
subscription.updated
subscription.active
subscription.canceled

Forward to Localhost

Use HookSense CLI to forward Polar webhooks directly to your local development server:

npx hooksense listen -p 3000 --path /api/integrations/polar

No ngrok or tunnel setup required. Install with npm i -g hooksense or use npx.

Tips & Best Practices

  • Polar uses the Standard Webhooks spec (webhook-id / webhook-timestamp / webhook-signature) — the same scheme as Svix
  • The signature base is webhook-id.webhook-timestamp.rawBody — verify against the raw body
  • Polar can format payloads for Discord or Slack too — point those at separate HookSense endpoints to compare
  • Replay captured order.paid events to retest fulfillment without a real purchase

Related

Polar Webhook Documentation Polar webhook tester — send sample events HMAC signature calculator
Webhook SignatureRaw Body2xx ResponseIdempotency

Give your agent a Polar callback

Create a free callback endpoint and have an agent await its first verified Polar webhook over MCP. Paid plans are early-access.

Get Started Free