In general, all responses come into the following types:

Informational responses (100 – 199)
Successful responses (200 – 299)
Redirection messages (300 – 399)
Client error responses (400 – 499)
Server error responses (500 – 599)

If your request was successful, you will receive a response with code 200 or 201 and the queried data in JSON format. Otherwise, you get an error response with a message telling you what was wrong with your request and what you can do to get the queried data.

Below are possible error responses you may get:

Response	Code	Description
Bad Request	400	One or more query parameters are wrong or missing.
Unauthorized	401	No or incorrect API key is entered in the query header.
Forbidden	403	The queried endpoint can't be accessed. This typically happens if you're trying to get data from a Pro endpoint without the necessary subscription.
Not Found	404	The queried address, transaction, coin, or object doesn't exist. This usually happens when you enter an incorrect hash.
Method Not Allowed	405	The server knows the request method, but the target resource doesn't support this method.
Request Timeout	408	The server timeout was due to a slow request caused by an idle connection.
Payload Too Large	413	The requested data is larger than the limits defined by the server. The server might close the connection or return a Retry-After header field.
Unsupported Media Type	415	The server rejects your request since the requested data is not supported in the media format.
Too Many Requests	429	You have insufficient API credits, or you have exceeded the permitted number of queries per minute. You can upgrade your subscription plan or wait for the next month to start. Otherwise, reduce the query frequency.
Internal Server Error	500	The server has encountered a situation it does not know how to handle.
Gateway Timeout	504	The server acting as a gateway cannot get a response in time.