Define · validate · copy

Generate a webhook payload from a small event contract

Define an event name and typed fields, then create a deterministic example payload locally for documentation and test fixtures.

Generator testedReviewed 2026-07-18

Event contract129 characters

Result

Your checked result will appear here.

DeterministicEach field type maps to one visible example value.LocalNo contract or payload is sent from this tab.Reviewed2026-07-18

Validate the event contract before constructing the envelope

The field map crosses a small set of explicit checks. Only then does the tool place example values inside a fixed, recognizable event envelope.

Typed event field tiles passing through validation checkpoints into a sealed payload card — A compact contract passes validation before it becomes a sealed fixture; the test endpoint remains a separate step. Original MCXAI artwork.

One small contract produces one repeatable fixture

The generator does not guess a vendor schema. You name the event and its top-level fields, and the output follows those choices.

1Name the event
Use two or more lowercase dot-separated segments, such as invoice.paid or account.created.
2Declare field types
Map each field to string, integer, number, boolean, null, object or array.
3Build obvious examples
Strings receive an example_ prefix; IDs and timestamps in the envelope are fixed test values.
4Copy, then adapt
Use the result in documentation or a controlled test fixture. Replace values only with invented, non-sensitive examples.

The exact contract and payload covered by the test

The output is intentionally stable. Re-running this contract does not create a misleading fresh timestamp or a production-looking identifier.

Event contract

{
  "event": "invoice.paid",
  "fields": {
    "invoice_id": "string",
    "amount_cents": "integer",
    "paid": "boolean"
  }
}

Generated fixture

{
  "id": "evt_example_001",
  "type": "invoice.paid",
  "occurred_at": "2026-01-01T00:00:00.000Z",
  "data": {
    "invoice_id": "example_invoice_id",
    "amount_cents": 1,
    "paid": true
  }
}

Rejected eventinvoice paid

Spaces do not form a stable event namespace. Use a name such as invoice.paid.

A payload fixture is only one part of webhook testing

Generation proves that the example matches this small contract. It does not prove delivery, authenticity, retry behavior or consumer compatibility.

Signature verification

Test the provider's real signing algorithm, timestamp tolerance and constant-time signature comparison separately.

Retries and duplicates

Assume delivery can repeat. Verify idempotency using a durable event identifier, not a process-local flag.

Ordering

Do not assume two related events arrive in creation order unless the provider explicitly guarantees it.

Schema evolution

Test omitted, added and unknown fields so a compatible consumer does not fail on a harmless extension.

This page generates JSON; it never delivers a request

Keeping generation separate from sending avoids accidental calls to production endpoints and makes the privacy boundary easy to verify.

This generator creates a fixture; it does not send HTTP requests
The timestamp and event ID are obvious fixed examples, not production identifiers
The contract accepts 1 to 50 top-level fields and is limited to 50,000 characters
Do not use real customer records, access tokens, webhook secrets or private endpoint URLs as examples.
Use an isolated test receiver when you later exercise actual delivery.

Preparing the page

Public context is loading before any interactive tool code.

Define · validate · copy

Generate a webhook payload from a small event contract

Define an event name and typed fields, then create a deterministic example payload locally for documentation and test fixtures.

Generator testedReviewed 2026-07-18

Event contract129 characters

Result

Your checked result will appear here.

DeterministicEach field type maps to one visible example value.LocalNo contract or payload is sent from this tab.Reviewed2026-07-18

Validate the event contract before constructing the envelope

The field map crosses a small set of explicit checks. Only then does the tool place example values inside a fixed, recognizable event envelope.

One small contract produces one repeatable fixture

The generator does not guess a vendor schema. You name the event and its top-level fields, and the output follows those choices.

1Name the event
Use two or more lowercase dot-separated segments, such as invoice.paid or account.created.
2Declare field types
Map each field to string, integer, number, boolean, null, object or array.
3Build obvious examples
Strings receive an example_ prefix; IDs and timestamps in the envelope are fixed test values.
4Copy, then adapt
Use the result in documentation or a controlled test fixture. Replace values only with invented, non-sensitive examples.

The exact contract and payload covered by the test

The output is intentionally stable. Re-running this contract does not create a misleading fresh timestamp or a production-looking identifier.

Event contract

{
  "event": "invoice.paid",
  "fields": {
    "invoice_id": "string",
    "amount_cents": "integer",
    "paid": "boolean"
  }
}

Generated fixture

{
  "id": "evt_example_001",
  "type": "invoice.paid",
  "occurred_at": "2026-01-01T00:00:00.000Z",
  "data": {
    "invoice_id": "example_invoice_id",
    "amount_cents": 1,
    "paid": true
  }
}

Rejected eventinvoice paid

Spaces do not form a stable event namespace. Use a name such as invoice.paid.

A payload fixture is only one part of webhook testing

Generation proves that the example matches this small contract. It does not prove delivery, authenticity, retry behavior or consumer compatibility.

Signature verification

Test the provider's real signing algorithm, timestamp tolerance and constant-time signature comparison separately.

Retries and duplicates

Assume delivery can repeat. Verify idempotency using a durable event identifier, not a process-local flag.

Ordering

Do not assume two related events arrive in creation order unless the provider explicitly guarantees it.

Schema evolution

Test omitted, added and unknown fields so a compatible consumer does not fail on a harmless extension.

This page generates JSON; it never delivers a request

Keeping generation separate from sending avoids accidental calls to production endpoints and makes the privacy boundary easy to verify.

This generator creates a fixture; it does not send HTTP requests
The timestamp and event ID are obvious fixed examples, not production identifiers
The contract accepts 1 to 50 top-level fields and is limited to 50,000 characters
Do not use real customer records, access tokens, webhook secrets or private endpoint URLs as examples.
Use an isolated test receiver when you later exercise actual delivery.

Start with your source

Validate the event contract before constructing the envelope

One small contract produces one repeatable fixture

The exact contract and payload covered by the test

A payload fixture is only one part of webhook testing

This page generates JSON; it never delivers a request

Inspect the JSON before testing a receiver

Start with your source

Validate the event contract before constructing the envelope

One small contract produces one repeatable fixture

The exact contract and payload covered by the test

A payload fixture is only one part of webhook testing

This page generates JSON; it never delivers a request

Inspect the JSON before testing a receiver