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Security for your users.
With your users.

A fully automated, user-centric approach to account security. Continuous risk-based authentication, response, and automated recovery.

End-to-end solution to prevent threats beyond account takeover

Castle was built for one single purpose – protecting your users. Castle detects threats like automated credential stuffing attacks and human-powered account takeovers, and automates the recovery process so you can breathe easy with zero false lockouts, support queues, or angry tweets.
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User-Trained Risk Engine

Learn from your users. Continuous user feedback trains the machine learning based on approved or “good” behavior from your users.

Automate Account Recovery

No lockouts, complaints, or drops in your core business metrics. Orchestrate and automate a process that gives security and customer service a hand.

More Context, Less Risk

Make better decisions with transparent insights and context into every threat signal, risk score, and event tracked per device within a user’s account.

Granular Access Policies

Align risk with your business objectives. Create granular risk policies with customized logic, risk scores, and responses based on custom scenarios.

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When it’s this easy, taking responsibility is a no-brainer

Sites and applications that utilize Castle are in a better position to protect, defend, and look out for their users. Our objective: Make it easy for security teams and developers to take on a guardian role. Castle's free trial and entry-level plans allow any online business to offer consumer-grade account security.
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World’s leading online brands choose Castle

“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.”


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“The benefit of Castle is that account takeover is a total non-issue now.”


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By developers, for developers

No on-prem installations. No single points of failure. Castle’s developer-first platform is built by, and for, those who want to REST easy. Deconstruct Castle into basic blocks to secure any UX your team dreams up.
verdict = castle.authenticate(
  event: '$login.succeeded',
  user_id: 'user1234'

puts verdict[:action] # => "allow", "challenge" or "deny"
CastleContext context = castle.contextBuilder()

Verdict verdict = castle.client().authenticate(

$verdict = Castle::authenticate(array(
  'event' => '$login.succeeded',
  'user_id' => 'user1234'

echo $verdict->action;
verdict = castle.authenticate({
    'event': '$login.succeeded',
    'user_id': 'user1234'

const response = await castle.authenticate({
  user_id: "user1234",
  context: Castle.getContext(request),

var result = await castle.Authenticate({
  Event = Events.LoginSucceeded,
  UserId = "user1234",
  Context = Context.FromHttpRequest(Request)

Cloudflare Integration

Protecting your company is now simpler with Cloudflare.

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Schedule an introductory call and live demo with a Castle security specialist.
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