Global Conventions

X-API-Key Header

The X-API-Key or x-api-key (case-insensitive) request header is the authentication method that Subscan API uses to determine the identity and rate limits.

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Rate Limiting

Each Subscan API key has a request quota, for example, 30 requests per second at most.

Currently, the quotas are global - shared across all APIs, all networks, and all client IP addresses as well. For instance, if an API key has a quota of 10 requests per second:

• Client A requests https://polkadot.api.subscan.io/api/now with an API key;
• Simultaneously, client B requests https://kusama.api.subscan.io/api/scan/metadata with the same API key.
• After these 2 requests, only 8 requests with the same API key are allowed in that second.

Subscan API respects the Internet-Draft RateLimit Header Fields for HTTP. Through the headers of any response, it is simple to retrieve the limit (ratelimit-limit), remaining quota (ratelimit-remaining), and the seconds until the limit resets (ratelimit-reset) of your key. For example, send any request:

curl -isS -X POST -H "x-api-key: YOUR_KEY" https://kusama.api.subscan.io/api/now

An example of partial response headers:

ratelimit-remaining: 7
ratelimit-limit: 10
ratelimit-reset: 22

If the client reached the rate limit, all other requests in the time slot will be throttled with an HTTP 429 Too Many Requests response that contains a retry-after header.

An example of partial response headers:

retry-after: 4
ratelimit-remaining: 0
ratelimit-limit: 10
ratelimit-reset: 4

An example of response body:

{
  "message":"API rate limit exceeded"
}

HTTP Status Codes

The table down below lists several HTTP status codes that Subscan might respond.

Code	Meaning
200 OK	The request was handled without any error.
401 Unauthorized	The credentials is either not found or invalid. Please refer to the message field in the JSON response for more detail.
404 Not Found	The HTTP method or request URI was most likely wrong.
429 Too Many Requests	The request hits the rate limit. Please request an API key with higher quotas.
500 Internal Server Error	The servers could not respond your request due to an internal error. Find more information on our status page.
502 Bad Gateway	The servers could not respond your request due to an internal error. Find more information on our status page.
503 Service Unavailable	The services were under maintenance. Please try again later.
504 Gateway Timeout	The servers could not respond your request due to an internal error. Find more information on our status page.