> For the complete documentation index, see [llms.txt](https://docs.link11.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.link11.com/using-link11/api/api-errors.md).
# API Errors
The table below describes error messages that can be received by API clients, and their meaning.
{% hint style="info" %}
**Note**: the API error numbers (e.g., 401, 500) do *not* refer to HTTP codes.
{% endhint %}
| Error Name | Explanation | Code |
| -------------------------------- | -------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| 500 missing API-key | Request without API Key | HTTP/2 200
server: nginx/1.16.0
date: Tu,21.06.2022 10:30:02 GMT
content-type: text/html; charset UTF-8
500 No api key supplied
|
| 500 invalid API-key | Request with invalid API Key | HTTP/2 200
server: nginx/1.16.0
date: Tu,21.06.2022 10:30:02 GMT
content-type: text/html; charset UTF-8
500 Invalid api key supplied
|
| 500 invalid domain-key | Request with incorrect Domain Key or *from non-whitelisted IP* | HTTP/2 200
server: nginx/1.16.0
date: Tu,21.06.2022 10:30:02 GMT
content-type: text/html; charset UTF-8
500 Invalid domain key
|
| 401 missing or invalid parameter | Request with missing or invalid parameters | HTTP/2 200
server: nginx/1.16.0
date: Tu,21.06.2022 10:30:02 GMT
content-type: text/html; charset UTF-8
401 Operation failed
|