Test GitHub webhooks without deploying

Capture push, pull request and release events from a repository or organisation, and verify X-Hub-Signature-256.

Get a URL that accepts the webhook#

A capture URL takes any method, any body, and records exactly what arrived: method, headers, query string, body and source IP. You do not need an account to make one, and an anonymous URL is deleted after 24 hours.

bash·No signup required

curl -X POST https://mocklane.com/api/v1/anon/endpoints \
  -H "Content-Type: application/json" -d '{}'

# The response carries a capture URL of the form:
#   https://mocklane.com/h/<endpoint-id>

Paste that URL into GitHub at Repository or organisation Settings, Webhooks, Add webhook, then trigger something. Events worth starting with:

push
pull_request
issues
release
workflow_run

Verify the X-Hub-Signature-256 header#

GitHub signs each request so you can tell a real delivery from anyone who has guessed your URL. The digest is HMAC-SHA256 over the raw body, hex-encoded, keyed with your secret, set on the webhook itself.

Header: X-Hub-Signature-256
Value format: sha256=<hex digest>
Algorithm: HMAC-SHA256, hex
Signed content: the raw body

javascript·Verify in Node

const crypto = require("crypto");

// The digest is prefixed, so build the whole header value and compare that.
const expected =
  "sha256=" +
  crypto
    .createHmac("sha256", process.env.GITHUB_WEBHOOK_SECRET)
    .update(rawBody)
    .digest("hex");

const ok = crypto.timingSafeEqual(
  Buffer.from(expected),
  Buffer.from(req.headers["x-hub-signature-256"]),
);

Compare digests with a constant-time function such as crypto.timingSafeEqual. A plain === returns as soon as two bytes differ, and that timing difference is enough to recover a valid signature one byte at a time.

What catches people out#

X-Hub-Signature, without the -256, still exists and uses SHA-1. It is kept for legacy consumers only. Verify the SHA-256 header.
The value includes the sha256= prefix. Comparing a bare hex digest against the header will never match.
A webhook with no secret configured is not signed at all, and GitHub will not warn you about it.
The payload must be hashed exactly as received, as UTF-8, with no reformatting.

Replay it until your handler is right#

A captured request can be re-sent to your own endpoint, with the body or headers edited first. That turns a bug that needed a real GitHub event into something you can reproduce on demand, which matters most for events that are awkward to trigger twice.

Assert on it in CI#

A scenario chains the steps into one run that passes or fails, so a change that breaks your GitHub handling fails the build rather than reaching production.

yaml·scenario.yaml

steps:
  - type: send_webhook
    body: { event: "push" }

  - type: wait_for_webhook
    timeout_seconds: 30
    assert:
      - status_code equals 200

Triggered from CI with an API token. See the scenarios documentation for the full step list.

Everything above is on the free plan, and the capture URL works before you sign up. Create a free account to keep a URL for longer than 24 hours.

Signature details checked against GitHub’s documentation on 22 October 2026. Schemes change: if this page and their docs disagree, believe theirs and tell us.