Webhook

What is a Webhook?

A Webhook (also called an HTTP callback or reverse API) is a mechanism in which a system sends an HTTP POST request to a pre-specified URL when a defined event occurs within it — a new invoice, a change in order status, an incoming payment. This is the opposite of a classic API call, where the client asks the server (“do you have anything new?”). A webhook is push; a classic API query is pull.

Advantages of webhooks:

• Real-time — the event is delivered immediately, without periodic polling
• Efficiency — no load on either system from empty calls
• Simplicity — configuration is typically just a URL + authentication token

Typical issues to keep in mind when implementing a webhook:

• Authentication — add an HMAC signature or token to verify the sender
• Retry logic — if the target system responds with an error (5xx), retry with exponential backoff
• Idempotency — the target system must handle receiving the same event twice
• Order of delivery — webhooks are not guaranteed to arrive in order

In the SaaS ecosystem, webhooks are a standard — Stripe, Shopify, Mailchimp, and many other platforms all use the webhook model.

When it is used

Webhooks are suitable for:

• Synchronisation between systems (ERP ↔ online store)
• Triggering workflow automation on an event
• Notifications to communication channels (Slack, Teams)
• Real-time dashboards

See the API page, the Workflows module, and integrations.

Related terms

• API — the classic request/response model. See /en/glossary/api.
• Workflow automation — webhooks are a typical trigger. See /en/glossary/workflow-automation.
• MCP — an alternative protocol for AI assistants. See /en/glossary/mcp.

In Modulario

Modulario exposes configurable webhooks for every key event — invoice creation, deal close, order status change. Automatic retry with signature ensures reliable delivery. Examples and schemas at /api.

Modulario provides a webhook management UI where an administrator can see all active registrations, logs of the last 1,000 calls (including payload and response), and can trigger a “replay” to re-deliver events after a target system outage.