The API enforces per-client rate limits to ensure fair access for all subscribers.
Limits
| Window | Limit |
|---|---|
| Per minute | 100 requests |
| Per day | 10,000 requests |
Limits are applied per API key using a sliding window algorithm.
Rate limit headers
Every response includes headers for monitoring current usage:
| Header | Description |
|---|---|
X-RateLimit-Limit | Maximum requests allowed in the current window |
X-RateLimit-Remaining | Requests remaining in the current window |
X-RateLimit-Reset | Unix timestamp when the window resets |
Retry-After | Seconds to wait before retrying (only on 429 responses) |
Caching guidance
H2GC data is updated on a monthly cadence. Responses can be safely cached for the remainder of the month without risk of missing updates. A local cache significantly reduces the total request count and is the recommended approach regardless of rate limits.
Increasing limits
Organisations that require higher limits should contact the H2GC team to discuss available options.