Dual-Mode Webhook Lab

Debug Polar webhook signatures across two signing schemes, practice with authored fixtures, and wire an idempotent Next.js handler — without sending secrets to a third-party debugger.

Buy on Polar — $14

What’s in it

• Offline HTML lab: Polar HMAC legacy vs Standard Webhooks verify/sign
• Authored fixtures (order.paid, refund, cancel, customer state)
• Next.js App Router handler sketch using Polar helpers
• Idempotency notes: retries, disables, grant-once rules

What it is not

• Not a hosted webhook debugger
• Not a substitute for Polar’s official docs
• Not a live payment or entitlement service

More from Gumbosveins

• Launch Kit — $19 — go-live checklist + env packs
• Deploy Guard — $12 — offline Vercel env matrix

Free write-up: sandbox vs live webhooks