Polling vs Webhooks
Polling and webhooks solve the same problem – delivering server-side events to a client – but with opposite responsibility models. In polling, the client drives: it requests updates on a schedule. In webhooks, the server drives: it POSTs to a pre-registered URL when events occur. Both are built on plain HTTP and are universally compatible.
Polling has the client ask the server repeatedly: 'Is there anything new?' Webhooks have the server push updates to the client when they happen. Polling is simple to implement and works everywhere. Webhooks are more efficient for infrequent events but require the client to have a publicly accessible HTTPS endpoint. The right choice depends on event frequency, infrastructure, and latency requirements.
| Feature | Polling | Webhooks |
|---|---|---|
| Who initiates | Client pulls – requests on a schedule | Server pushes – sends when event happens |
| Latency | Up to poll interval (seconds to minutes) | Near-real-time – delivered within milliseconds of event |
| Efficiency | Wasteful – most polls return 'nothing new' | Efficient – only sends when there is data |
| Client requirements | Any HTTP client – no inbound access needed | Needs a publicly accessible HTTPS endpoint to receive calls |
| Reliability | Client controls retry – simple to make reliable | Server retries on failure – but delivery semantics vary by vendor |
| Security | Client authenticates to server – standard auth | Server authenticates to client – need to verify signature/secret |
| Implementation complexity | Low – a simple loop with sleep | Medium – need endpoint, TLS, signature validation, idempotency |
| Rate limit risk | High – aggressive polling hits rate limits | Low – only called when events occur |
| Firewall friendliness | Works behind NAT and firewalls – outbound only | Requires inbound HTTPS – problematic behind strict firewalls |
| Works in browser | Yes – fetch/XHR polls work natively | No – browsers cannot receive inbound connections |
| Best for | Frequent checks, browser clients, behind-NAT systems | Infrequent events, server-to-server, real-time integrations |
When to use Polling
Use polling when: the client is a browser, the client is behind a firewall or NAT without a public endpoint, events are frequent enough that the poll interval matches event frequency anyway, or the implementation must be simple. Also use polling when verifying webhook delivery during development.
When to use Webhooks
Use webhooks when: events are infrequent but latency-sensitive (payment confirmation, CI/CD triggers, GitHub events), the receiver has a stable public HTTPS endpoint, and you want to avoid unnecessary server load from empty poll responses. GitHub, Stripe, Twilio, and most SaaS platforms expose webhooks as their primary event delivery mechanism.
Common Mistakes
- Polling too aggressively – 1-second polling on an API that updates once per hour wastes bandwidth, burns rate limit quota, and adds server load with zero benefit.
- Not verifying webhook signatures – any server on the internet can POST to your webhook endpoint. Always verify the HMAC-SHA256 signature (X-Hub-Signature, Stripe-Signature, etc.) before processing.
- Not handling webhook idempotency – webhooks are delivered at-least-once. The same event may arrive twice. Store processed event IDs and deduplicate.
- Using long-polling as a polling optimization – long-polling (server holds the request open until an event occurs) is better than fixed-interval polling but is essentially poor-man's SSE. Use SSE or WebSocket instead of long-polling.
FAQ
What is long-polling and how does it compare?
Long-polling is a variant where the client makes a request and the server holds it open until an event occurs or a timeout expires. It reduces the number of empty poll responses but still requires the client to immediately re-request after each response. It is less efficient than webhooks, SSE, or WebSocket but works in environments where inbound connections are impossible.
Can I combine polling and webhooks?
Yes – this is a common pattern. Use webhooks as the primary delivery mechanism for low latency, and fall back to polling to reconcile any missed events (webhooks are not guaranteed-delivery). Stripe explicitly recommends polling the API to reconcile state if webhooks are missed or fail.