Keep out fake accounts.
Protect real ones.

Account security and fraud prevention for developers, teams, and enterprises.

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Johan Brissmyr
Known User
Castle API
Trusted by leading technology brands
Simple User Security

Seamless and simple
account security

Feed Castle any user event for real-time scoring and threat detection. Receive synchronous decisions to block spam registrations and account takeover attempts.

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Castle Risk Engine

Request is analyzed across a suite of intelligent risk models.

New Device
Fast Travel
IP Ratelimited
Tor Browser
New Country
New Device
Robotic Mouse Movement
Missing Client ID
Tool User Agent
Invalid Email
Leaked Email Credentials
New Region
Proxy Access
Missing Client ID
Tool User Agent
Invalid Client ID
Risk Score
Eliminate fake accounts

Less friction means higher conversion. Our invisible APIs let you simplify your registration flow while keeping the spam out of your system.

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Avoid credential stuffing

Get advanced credential stuffing protection straight out of the box with Castle's industry leading account takeover protection.

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Advanced bot detection

Whether it’s at registration, login, or anywhere in-app, Castle can screen any key user events to filter out the bad bots from the good ones.

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Security automation

Detection is only half the battle. Automate account recovery flows, step-up auth, or end user alerts with Castle Webhooks & Notifications.

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Your personalized
security stack

Castle profiles your app’s nuanced traffic, its unique users, and each device independently. By learning what’s normal for your app and your users, Castle uniquely identifies anomalies and risks.

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Detailed user insight

Castle builds baseline patterns of behavioral norms for each individual user in order to assess anomalies and risky behavior.

Robust device management

Castle's Device Fingerprinting for web, mobile, and APIs identifies each device with high fidelity, so they can be managed with accuracy.

Built for Scale

An API-based Integration

Castle’s open sourced SDKs help you secure events in any language.

Realtime event authentication
CastleContext context = castle.contextBuilder()

Verdict verdict = castle.client().authenticate(

Device fingerprinting
<script src=""></script>
_castle('setAppId', '451236789012343');
_castle('identify', 'user1234'); 

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.

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

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SOC 2 and GDPR Compliant

Meeting your organization’s ongoing compliance needs is a priority. We undergo independent third-party audits and certify our products with SOC 2, and more.

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Analytics and Insights

Clear visibility across
all your users

Castle builds profiles for each user to map out activity streams. Spotlight users at risk, dive into suspicious sessions, and see individual devices responsible for fraud.

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A successful integration is one that I don’t have to sit on to use and that can alert us with a minimal amount of false positives. That’s what we have with Castle.

Ken Pickering
VP of Engineering
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Get started in minutes

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

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