A webhook is an address on the internet that receives a notice when something happens in another application. Instead of asking every minute “any news?”, the application knocks on your door and hands over the data. You can test any webhook with curl, a command-line program that makes HTTP requests.
How it works
| Role |
Who |
What it does |
| Sender |
The application where the event happens (a shop, a form, a payment service). |
When something happens, it sends a request to an address you gave it, usually with the data as JSON. |
| Receiver |
Your program (n8n, a PHP file on your site, an application). |
Has a public address, reads the request and replies with a status code. |
| Reply |
The receiver. |
A code such as 200 says “got it”. Many senders try again if they do not get one. |
Testing with curl, step by step
| 1 |
Have the webhook address. It has to be public and, normally, HTTPS. A localhost address will not do: the sender, out on the internet, cannot reach your computer.
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| 2 |
A plain request, to see whether the address answers: curl -i https://n8n.asuaempresa.ao/webhook/your-path. The -i shows the status code and the reply headers.
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| 3 |
A request with data, the way the sender would send it: curl -i -X POST https://n8n.asuaempresa.ao/webhook/your-path -H "Content-Type: application/json" -d '{"name":"test"}'.
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| 4 |
Read the status code in the table below.
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| 5 |
See whether the receiver logged the request. In n8n, in the executions list; in your own code, in the error log.
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What the code means
| Code |
Means |
| 200 or 201 |
Received. If the rest fails, it fails inside the receiver. |
| 301 or 302 |
The address redirects. Many senders do not follow redirects: use the final address. |
| 401 or 403 |
Authentication is missing, or a firewall blocked it. See why your IP gets blocked. |
| 404 |
That path does not exist. On an n8n, it is nearly always the test address out of use or the workflow inactive: n8n webhooks. |
| 405 |
The method is wrong (GET instead of POST, or the other way round). |
| 500 |
The receiver got it and fell over. Look at the error on its side. website errors explained. |
| 502 or 504 |
A proxy in the middle could not reach the receiver, or it took too long. |
With no reply at all, the problem is earlier: the domain name, the port or the firewall. See which ports are open.
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An open webhook is an open door. Whoever knows the address can send you whatever they like. Always check who sent it (a secret in a header, a signature) before acting, and never trust the content as if it were your own. And be ready to get the same notice twice: senders repeat themselves.
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You can receive webhooks on an ordinary website: a PHP file that reads the request body (php://input) and stores or handles it. For workflows across several applications n8n is more comfortable, on a VPS; see what n8n is. For Meta’s, webhooks from Meta.
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