Product review
Castle account sharing detection review
Castle documents account-sharing detection using unique devices per account, optional IP-count conditions and configurable policies. Its tutorial makes the operating trade-off explicit: an aggressive short window can be softened with more devices, a wider window, fewer IP conditions or a challenge instead of a denial. Tracking relevant activity matters when a login session stays active for a long time.
Key facts
- Sharing metrics
- Use the number of unique devices associated with an account, with optional IP metrics and a selected time window. Adjust thresholds to the actual subscription policy. Source ↗
- Coverage and timing
- Tracking additional account activity improves visibility beyond the original login. A long-lived session can otherwise hide overlapping usage. Source ↗
- Response
- Policies can allow, challenge or deny. The tutorial recommends tuning the account-sharing rule and response to reduce legitimate-user friction. Source ↗
- Access
- Pro: 200 US dollars monthly API credit; equivalent to 40,000 Risk calls. Enterprise from 4,000 per month; free monthly credit is 5 US dollars, equivalent to about 1,000 Risk calls or 5,000 IP calls. Source ↗
Strengths
- Specific sharing tutorial with metrics, windows and response guidance.
- Configurable policies and inspectable account/device evidence.
- Useful credit-based entry for an engineering pilot.
Limitations
- The team must configure and maintain account-sharing policies.
- Login-only instrumentation can miss ongoing activity in long-lived sessions.
Who it fits
Security and product engineers who want documented account-sharing metrics with configurable response policies.
Compare the alternatives by account-sharing scope when your team needs a different relationship output or operating model.
What the score means
The editorial score of 8.6 out of 10 places this tool in the published comparison. It reflects product fit under the same 34-criterion, six-category framework used for all ten tools.
The facts above help evaluate persistent identity, household handling, sharing specificity, session context, response and practical access. Read every criterion and weight.
How to evaluate it
Implement the documented unique-device metric for one test subscription. Compare a short-window device burst with sequential use and a legitimate replacement device. Test challenge or review before deny.
Self-serve evaluation account
The Free plan is an account-based evaluation route with published limits, not an anonymous browser checker.
Open evaluation routeUse the public route to inspect access and output, then validate the product on your own permitted traffic.
Sources and further reading
- Product and detection approach · checked October 21, 2026
- Pricing and access · checked October 21, 2026
- Integration and result documentation · checked October 21, 2026
- Account-sharing use case and operating model · checked October 21, 2026
FAQ
Is sharing the same as multiple accounts per device?
No. Sharing examines multiple devices using one account. Multiple accounts per device examines the reverse relationship; choose the correct metric and policy.
Can Castle use a softer response?
Yes. Its policies and account-sharing tutorial support tuning thresholds and using challenge or review instead of immediate denial.
Why track activity after login?
Long-lived sessions can overlap without another login event. Relevant activity gives account metrics a more complete history.
Explore checkers, demos and evaluation routes →