Rupt vs. Castle
Castle offers similar functionality to Rupt but differs in the depth of the offering and how much you build on top of it, and how customizable each product is.
The short version
Updated August 2026
- Castle focuses on the decisioning layer for well-defined workflows without the need for tailored customizations.
- It provides a good rules engine, and many of the important signals. It lacks the challenge engine, deeper signals, and offers no AI agent capabilities.
- Rupt is a full fraud engine. It includes fingerprinting, email and phone intelligence, a rules engine, hosted challenges, and an AI agent that investigates accounts and monitors for new patterns.
- Overage is $0.005 per call on both. The difference is how much of the stack is included in that number and what kind of support you get.
Capabilities.
Checked against both products' public pricing pages and docs, August 2026.
Why choose Rupt.
Account-centric by design
Every device, IP, and action rolls up to the user behind it. You investigate accounts, not anonymous requests, and the full history is already assembled when you get there.
Continuous monitoring
Every signup, login, and sensitive action is evaluated, so an account's risk is tracked across its lifetime and new patterns surface as they form, not after the damage.
Automated challenges
Risky actions trigger hosted email or SMS challenges automatically. Legitimate users clear them in seconds, attackers don't, and nobody on your team had to send anything.
A force multiplier for risk teams
Detection, decisioning, and enforcement run continuously without headcount. A team of one gets real coverage, and an established team spends its hours on judgment calls instead of triage.
AI-driven investigations
The AI agent digs into flagged accounts and watches for emerging abuse patterns around the clock, so your team reviews conclusions instead of assembling evidence.
Coverage across the whole journey
Evaluations are priced to run everywhere, from signup to checkout to content access, so you see the account's behavior end to end instead of a snapshot at the login gate.
Support that isn't gated behind Enterprise
Integration setup help, developer meetings, and direct Slack and email access with replies in hours come with every plan. Most vendors reserve that level of support for their top tier; with Rupt it's just how support works.
Single-vendor pricing
Fingerprinting, email and phone intelligence, rules, and challenges usually mean a vendor and an invoice each. Because Rupt ships them together, the bundle costs less than the sum of the point tools.
Migrating from Castle.
- 01
Swap the client SDK. Load Rupt's snippet and call evaluate() on login, signup, and the actions you care about, the same places you generate Castle request tokens today.
- 02
Replace the risk call. Where your server sent a request token to Castle, read the Rupt evaluation instead: one GET returns the verdict, named risks, fingerprint, and device ID. Castle's numeric risk scores map to Rupt's named risks and allow / challenge / block verdicts, so your score thresholds become policy conditions.
- 03
Run both vendors for two to four weeks. Device IDs won't map one to one, so let returning users re-identify while you compare Rupt verdicts against Castle scores on the same traffic.
- 04
Turn on policies in observe mode, watch the verdicts, then enforce. If you built a step-up flow for Castle, you can retire it: a challenge verdict hands off to Rupt's hosted flow.
Frequently asked questions.
See Rupt on your traffic.
Book a demo and we'll walk through your use case, show you the signals on real evaluations, and price out your volume.
- A walkthrough tailored to your use case.
- How detection, the rules engine, and challenges fit your stack.
- Pricing and a rollout plan for your volume.