Easy-to-use APIs to power your dream security

Our goal is to provide your users with a secure and frictionless security experience. All of your basic use cases can be covered through a handful of endpoints. You send us an event, we evaluate it, and return an inline verdict. Your brand. Your users. Castle’s Intelligence.

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Realtime event authentication
CastleContext context = castle.contextBuilder()

Verdict verdict = castle.client().authenticate(

Device fingerprinting
<script src="https://d2t77mnxyo7adj.cloudfront.net/v1/c.js"></script>
_castle('setAppId', '451236789012343');
_castle('identify', 'user1234'); 

Security without compromise

Evaluate any user event for suspicious or bot-like activity using our sychronous /authenticate endpoint. Get a response in under 50 ms.

Flexible 3-tier verdict system

Receive inline risk verdicts that map to one of three recommended actions: Allow, Challenge, or Deny. Use these verdicts to protect, notify, and recover user accounts.

Built for consumer scale

Our APIs are flexible and easy-to-use while being powerful enough to handle unicorn-sized user bases.

SDKs for all languages

We have open source SDKs published for popular programming languages to help you get started quickly. You can review them all from our un-gated developer docs.

Tools for Developers

Suite of tools to help developers get started

Our support teams are always ready to help you through but we also provide a variety of tools to help you get started quickly and make the most of Castle. These come in the form of interactive training guides, an intuitive debugging console, and test scripts to quickly test our APIs.

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Reliability & Scale

Built for consumer-grade applications

We support thousands of developers, and leading technology brands from all across the globe.

Avg. response time

Our products are designed to power user exeperiences inside leading applications. Low latency response times over secure APIs is a top priority.


Castle's integration model ensures it is never a single point of failure. Enterprise SLAs guarantee service uptimes to handle scale with confidence.


Meeting your organization’s ongoing compliance needs is a priority. You control what data to send us, and can programmatically purge user data at any time.

Try for free

Get started in minutes

You can test and deploy a fully automated, user-centric approach to account security for free.

Create Free Account