National Institute of Standards and Technology (NIST) · Rate Limits

Nist Rate Limits

NIST publishes explicit rate limits for the National Vulnerability Database (NVD) API. Anonymous callers get 5 requests per 30-second rolling window; callers with a free API key get 50 requests per 30-second rolling window. Other NIST APIs (NIST Chemistry WebBook, Internet Time Service) do not document per-key limits but are subject to firewall-level DOS protection. NIST recommends a 6-second sleep between requests to stay within compliance.

Nist Rate Limits is the machine-readable rate-limit profile for National Institute of Standards and Technology (NIST) on the APIs.io network, in the API Commons Rate Limits shape.

It captures 3 rate-limit definitions, measuring requests_per_30_seconds and requests_per_second.

An exhausted limit returns HTTP 403.

This profile was written by API Evangelist and has not been verified against a page the provider published; treat every limit as unconfirmed until a dated transcription replaces it.

The profile also includes 4 backoff/retry policies defined and response codes documented for throttled and forbidden.

Tagged areas include Rate Limiting, Cybersecurity, Government, and Public Data.

3 Limits Exhausted: HTTP 403
Method: generated, dated 2026-05-05.
Written by API Evangelist on 2026-05-05 and not verified against a page the provider published. Treat every limit as unconfirmed until a dated transcription replaces it.
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Rate LimitingCybersecurityGovernmentPublic Data

Limits

NVD API — Anonymous IP
requests_per_30_seconds · second
5
30-second rolling window. Recommended 6-second sleep between requests.
NVD API — API Key api_key
requests_per_30_seconds · second
50
30-second rolling window. 10x increase over anonymous.
Other NIST APIs (Chemistry WebBook, Time Service, etc.) IP
requests_per_second
see firewall fair-use policy
No published per-key RPS; firewall enforces DOS protection.

Policies

6-second sleep recommendation
NIST recommends sleeping ~6 seconds between requests so legitimate requests are not blocked by firewall DOS protection.
Free API key registration
API keys are free and obtained via the NVD developer portal — request, accept Terms of Use, and activate via email link.
Firewall-level enforcement
NIST firewall rules apply at the perimeter; 403 responses indicate firewall throttling rather than application-level 429.
Spread queries
For full NVD ingest, paginate with resultsPerPage=2000 and use lastModStartDate / lastModEndDate windowed sync rather than re-querying the full dataset.

Sources

Work with this as data

Every rate limit here is available over the APIs.io API and to AI agents over MCP.

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Tools for rate limits

4 MCP tools reach this
  • find_rate_limitsBrowse and filter every rate limit in the catalog.
  • apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
  • resolveTurn a domain, URL or GitHub org into the provider it belongs to.
  • find_cohortsEvery scored population of providers in the catalog.
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Call it yourself

curl for this page
This rate limit 
curl "https://apis.io/api/v1/rate-limits/nist-rate-limits"
All rate limits 
curl "https://apis.io/api/v1/rate-limits?limit=25"

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