> For the complete documentation index, see [llms.txt](https://docs.tumbler.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tumbler.app/after-first-launch/fetcher-restrictions.md).

# Fetcher client restrictions

## Who this is for

Providers who want to serve fetcher-agent requests correctly and protect their infrastructure.

## What you can do

* Configure an IP/ASN allowlist or User-Agent allowlist.
* Rate limit fetcher requests without blocking clients.
* Communicate TLS and error-response requirements.

## Examples

* User-Agent: `tumbler-backend-fetcher/1.0`
* Rate limit: up to 1 request per second per subscription.
* `429` response with Retry-After 60 when the limit is exceeded.

## See also

* [operations/reliability-and-timeouts.md](/after-first-launch/reliability-and-timeouts.md)
* [operations/caching-and-304.md](/after-first-launch/caching-and-304.md)
* [operations/fetcher-http-contract.md](/subscription-contract/fetcher-http-contract.md)
* [security/url-protection-and-crypt3.md](/getting-started/url-protection-and-crypt3.md)

## Rules

* Do not block the fetcher by GeoIP; use an explicit IP or CIDR allowlist agreed in advance.
* Support valid TLS, modern ciphers, and SNI.
* Return precise error codes: 429 for rate limits, 403 for access denial, 5xx only for real failures.
* Do not require stateful cookies; stateless tokens or signatures are preferred.

## Rate limiting

* Configure conservative limits: 1-2 rps is enough for most providers.
* Include `Retry-After` for predictable client behavior.
* When the limit triggers, do not change the response body (you may return JSON with `error` and `retry_after`).


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