What Castle does

Castle is a San Francisco-based security SaaS company founded in 2015 that provides account security, bot detection, and fraud prevention for developers, security teams, and enterprises. The platform is structured around a dual-layer architecture: edge-level request analysis (deployed natively through a no-code Cloudflare integration) combined with in-app SDK-based session, device, and behavioral tracking. Signals flow between the two layers so that early edge blocks sharpen downstream in-app catch rates. Core capabilities include 99.5% accurate device fingerprinting, self-learning AI risk scoring (Abuse, Account Takeover, and Bot scores), a no-code rules engine for real-time allow/challenge/deny actions, email intelligence for disposable domain and enumeration detection, network analysis linking bad actors across shared devices/IPs/payment methods, and analytics over up to 18 months of historical data. The product surface is exposed through a Risk API v2 and a JavaScript SDK (castle-web v2.1.8).

Castle monetizes through a consumption-based SaaS subscription — a free tier of 1,000 requests per month at $0 plus usage-based pricing scaled on API requests or Monthly Active Users under a transparent pay-as-you-go model with no contracts. Go-to-market is product-led growth with an API-first, developer-friendly distribution model: self-serve signup via dashboard.castle.io, monitoring mode before blocking, and a no-code Cloudflare edge deployment. The customer base is horizontal — any SaaS platform managing user accounts is in scope — with named enterprise logos including Sinch and GoTo. Castle reports processing billions of monthly API requests with sub-100ms response times and publishes open-source research, including monthly top-2,000 fraudulent email domain lists.

The company is legally organized as Castle Intelligence, Inc. in the United States, is SOC 2 Type II certified and GDPR compliant, and has raised approximately $11.56 million across disclosed rounds (2015 pre-seed of $360K, 2016 seed of $2M led by First Round Capital, 2019 Series A of $9.2M led by Index Ventures, and a 2021 investment from Page One Ventures). Leadership comprises co-founder and CEO Johan Brissmyr, co-founder and Chief Architect Sebastian Wallin, COO Jim Gochee, and Principal Solutions Architect Tom Smith. A dedicated research team focused on bot detection and adversarial AI was formally established in March 2026.

Name

Castle

Legal name

Castle Intelligence, Inc.

Website

https://castle.io

Company type

Private

Founded year

2015

Operating status

Operating

Headcount range

11–50 employees

Short description

Castle is a San Francisco-based security SaaS company founded in 2015 that provides dual-layer bot detection, device fingerprinting, and account-fraud prevention to SaaS platforms, developers, and enterprise security teams via a Cloudflare-native edge integration and an in-app Risk API.

Ownership category

akta.pro rank

Product category

Fraud Detection Software

NAICS

Security Guards and Patrol Services (561612), Security Systems Services (except Locksmiths) (561621)

akta.pro primary industry

Marketplace & Platform Trust & Safety (Buyer/Seller Abuse) (HDADALAI)

akta.pro secondary industry

Risk Scoring, Decisioning & Orchestration (FSAMALAB)

Keywords

• Fraud prevention
• Bot detection
• Account security
• Device fingerprinting
• Account takeover protection

Headquarters

HQ city

San Francisco

HQ country

United States

HQ region

North America

Markets served

GTM type

B2B

Offering type

Software

Cost components

Technology or R&D, Personnel, Operations, Infrastructure, Marketing or Sales

Revenue model

1. API / Request-based SaaS Subscription: Castle charges on a per-request or MAU (Monthly Active User) basis under a transparent pay-as-you-go model. Starting at $0 for 1,000 requests per month, plans scale with usage. This is a consumption-based SaaS subscription model.
2. Usage-based Request Pricing: Pricing scales with the number of API requests or MAU processed through the platform, providing predictable but variable costs for customers based on their traffic volume.

Pricing tiers

Go-to-market motion2 records

Distribution channels3 records

Marketing channels5 records

Core offering

Castle provides a dual-layer fraud defense platform that combines edge-level request analysis (via a no-code Cloudflare integration) with in-app SDK monitoring of sessions, devices, and user behavior. The platform exposes a real-time Risk API v2 and JavaScript SDK that return device, bot, account takeover (ATO), and abuse risk scores in under 100ms, along with email intelligence and a no-code rules engine. Customers start in monitoring mode and switch to blocking mode without DNS changes or contracts.

Product overview

Castle is a unified fraud defense platform designed to stop bots and account abuse. The platform operates through a dual-layer architecture combining edge-level analysis via Cloudflare integration with in-app SDK monitoring. The core offering includes the Castle Platform, Risk API v2, and castle-web SDK, supplemented by feature modules for Behavioral Analysis, Device Fingerprinting (99.5% accuracy), Bot Detection, AI Scoring (self-learning), Rules Engine, Email Intelligence, Case & State Management, and Analytics with 18-month historical data. The system processes billions of monthly requests with 100ms response time.

Differentiator

Problem solved

Functional benefit

Products and services

• Castle Platform A complete fraud defense platform combining edge-level abuse blocking (Cloudflare integration) with in-app SDK-based monitoring. Provides dual-layer protection where signals flow between the edge and in-app systems to sharpen detection across both layers. Targets SaaS platforms and online services that manage user accounts.
• Risk API v2 A real-time API that analyzes user events (logins, registrations, transactions) and returns threat insights including bot scores, account abuse scores, account takeover scores, device intelligence, and recommended policy actions within a 100ms response time. For developers and security teams building custom fraud-prevention integrations.
• castle-web SDK Client-side JavaScript SDK (version 2.1.8) for in-app user and device tracking. Tracks sessions, devices, and behavior enriched with business context to spot fake signups, account takeovers, and multi-accounting in real time. For engineering teams integrating fraud signals directly into web applications.

Quantifiable outcome

• 99.5% device fingerprinting accuracy
• +3 more outcomes

Segments1 record

Ideal customer profiles1 record

Technology focussed Yes

API detail

Has API

Yes

API docs

API detail

Core technology

AI maturity

App detail

Integration4 records

AI capability3 records

Feature10 records

Scale indicators4 records

Recent moves6 records

Expansion highlights6 records

Direct peers

• DataDome: DataDome is a leading bot management and account fraud prevention platform offering real-time detection at the edge and in-app, with comparable device fingerprinting, behavioral scoring, and SDK-based deployment models serving SaaS and e-commerce customers.
• HUMAN Security: HUMAN (formerly White Ops, which acquired PerimeterX) provides enterprise bot mitigation, account takeover prevention, and fraud defense with comparable SDK + edge architecture and serves overlapping mid-market and enterprise customers.
• Arkose Labs: Arkose Labs specializes in bot detection, account takeover prevention, and fake signup abuse with a risk-decisioning platform aimed at the same SaaS and consumer-facing use cases Castle targets.
• Kasada: Kasada offers bot management with deep device and behavioral fingerprinting, targeting credential stuffing, scraping, and account abuse for online businesses — a direct architectural and use-case competitor to Castle.
• Fingerprint (formerly FingerprintJS): Fingerprint provides highly accurate device identification and visitor intelligence APIs used for fraud prevention, account takeover, and signup abuse — overlapping significantly with Castle's device fingerprinting and Risk API.

Broad incumbents

• Cloudflare Bot Management: Cloudflare offers native Bot Management and Turnstile as part of its broader application security suite, reaching Castle's edge-layer customers via a bundled platform — comparable in capability but embedded in a much wider portfolio.
• Akamai Bot Manager: Akamai Bot Manager is part of Akamai's application security portfolio and addresses credential abuse, scraping, and account takeover for large enterprises — overlapping with Castle's space but sold as part of a broader CDN/security bundle.
• F5 (Shape Security): F5's Shape Security offers enterprise-grade fraud and abuse prevention, including bot management and ATO defense, targeting large financial services and e-commerce customers with a comprehensive application delivery stack.
• Imperva (Thales): Imperva provides application security including bot management, account takeover prevention, and API protection as part of a broader cybersecurity portfolio now under Thales — comparable use cases but a much wider product suite.

Emerging players

• SEON: SEON offers digital fraud prevention with device fingerprinting, email/phone intelligence, and behavioral analytics aimed at fintechs and online platforms — overlapping with Castle's risk-scoring and email intelligence modules.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat6 records

Key risks6 records

Key highlights7 records

Customer concentration

• Xx.com/Castle_io
• LinkedInlinkedin.com/company/castle-intelligence

Compliance2 records

Revenue estimate

Valuation estimate

Number of profiles

Profiles4 records

Funding overview

Funding rounds5 records

Investors14 records

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Castle