What is a mock API webhook (and how to make one free)
A mock webhook is a real URL that returns the response you define. Publish one from any payload in Yellorn, point your app at it, and watch requests arrive in an owner-only log.
What a mock webhook is
A mock webhook is a real HTTPS endpoint that returns a response you define. Instead of standing up a server, you publish a payload to a URL and point your app, a third-party service, or a curl command at it. It's ideal for testing a client, receiving a callback, or stubbing an API that isn't built yet.
Publish one in seconds
- Sign in (a free account is enough to publish).
- Put your response payload in the editor — JSON, XML, YAML, whatever your caller expects.
- Click Publish in the toolbar. You get a public URL back immediately. On Pro or Team, the caret beside Publish optionally lets you choose a custom endpoint path.
Anyone with the URL can call it — fetching the slug is public on purpose, so real services can send it traffic. The response's Content-Type matches the format you published.
Make the response dynamic
A fixed payload returns the same bytes every time. To return a fresh UUID, the current timestamp, a random value, or an echo of the incoming request, wrap a small expression in {{ … }} — see Return dynamic data from a mock API.
See every request (owner-only)
Each webhook has a private inspection portal, visible only to you. It logs every incoming request — method, headers, query string, and body — so you can confirm what your client actually sent. From the portal you can also set a canned response status code and clear the log.
Expiry, limits & custom paths
- Endpoints expire automatically after a set window (longer on paid plans) — mock URLs are meant to be temporary.
- Paid plans can publish to a custom, memorable path instead of a random slug.
- Decoding and inspection are owner-gated: only you can read the request log or change the response.
Frequently asked questions
What is a mock API webhook?
A mock webhook is a real HTTPS endpoint that returns a response you define, without you running a server. You publish a payload to a URL and point your app, a third-party service, or a curl command at it — ideal for testing a client, receiving a callback, or stubbing an API that isn't built yet.
How do I create a free mock API endpoint?
Sign in (a free account is enough), put your response payload in the Yellorn editor, and click Publish in the toolbar. You get a public HTTPS URL back immediately. Pro and Team users can optionally open the caret beside Publish to choose a custom endpoint path. The response's Content-Type matches the format you published.
Can the mock API return dynamic data?
Yes. Wrap a small Python-flavoured expression in {{ }} anywhere in the payload — {{ uuid4() }}, {{ now() }}, {{ randint(1, 100) }}, or {{ request.ip }} — and it renders fresh on every request. See the dynamic mock API responses guide for the full token reference.
Can I see the requests my mock endpoint receives?
Yes. Each webhook has a private, owner-only inspection portal that logs every incoming request — method, headers, query string, and body — so you can confirm exactly what your client sent. You can also set a canned response status code and clear the log there.
How long does a mock endpoint stay active?
Endpoints expire automatically after a set window (longer on paid plans) because mock URLs are meant to be temporary. Paid plans can also publish to a custom, memorable path instead of a random slug.
Related
Where to go next
Try a fix in the editor or browse more articles.