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Webhook senders are at-least-once: on a network blip or a non-2xx response they retry, so the same event can arrive more than once. Deduplication collapses those repeats into the one event you already captured — per endpoint, keyed however you choose — so a retry doesn’t show up (and count) twice. It’s off by default; turn on a mode when a sender’s retries get noisy.
Deduplication is best-effort load reduction, not an exactly-once guarantee. Keep your own handler idempotent — dedup reduces duplicates, it doesn’t promise their absence. Which mode keyed an event is recorded on the event object as dedupStrategy, alongside the derived dedupKey.

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The default

Every endpoint starts with deduplication off — we capture every request as a distinct event, and nothing is collapsed. That’s the safe default for an inspection tool: you see exactly what a sender sends, retries and all. Deduplication is opt-in; turn on a mode per endpoint once you trust a sender’s shape and want its retries folded away. For where dedup sits in the pipeline, see how webhook.co works.
With dedup off, every request is a distinct, counted event — including retries and any non-webhook traffic (uptime checks, link previews) that reaches the URL. Enable a mode to collapse retries; the soft cap pauses ingestion before a runaway sender runs away with your usage.

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Modes

Set a per-endpoint dedupConfig to turn deduplication on and choose how the key is derived: Every mode except off takes a windowSeconds (60–604800, i.e. 60s–7d), the window within which repeats collapse. off takes no window — it never collapses.
Collapsing is scoped to the window on purpose: a repeat that arrives in a later window is treated as a new event, so a legitimately-repeated payload days later is still captured rather than silently dropped. One consequence — a retry that lands right around a window boundary can be captured as two events, because the copies fall in different windows. If your sender supplies a stable id, prefer identifier: its key is that id and carries no window, so a retry collapses no matter when it arrives. content and fields keys include the window, so those are the modes where a boundary-straddling retry can double up. Widening windowSeconds makes a straddle rarer.

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Field paths

fields mode keys on values you select with field paths. A path starts with a root — headers, body, query, or path — and addresses into it with dot notation and array accessors:
  • body.data.id — a nested body value
  • headers.x-event-id — a header value
  • query.id — a query parameter
  • body.items[*].sku — every element of an array ([*] wildcard, or [0] for one index)
Provide include paths (the values that make up the key) and, optionally, exclude paths (volatile fields to drop, like a per-delivery timestamp). If a configured field is missing from a request, that request is treated as distinct rather than collapsed — webhook.co never silently drops an event it can’t key.

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Configure it

Deduplication is configured identically across every surface — set it on create, or update it any time. --dedup-reset (CLI) or a null dedupConfig (API) returns an endpoint to the default.
Config changes take effect within the cache-propagation window (about five minutes), not instantly — and a change never claims exactly-once across the transition. Every change is recorded in your endpoint’s tamper-evident audit trail.