Open Source Alternatives to Castle

Authentication and authorization for modern apps.

Open source

Device intelligence platform for fraud prevention, bot detection, and enhanced customer experiences.

Open source

Truffle Security provides a platform for continuous security testing and vulnerability management.

Open source

Open-source identity and authorization services for applications, offering composable and scalable IAM solutions.

Open source · Self-hostable

Ark Infotech offers Cybersecurity, AI/ML, Data Analytics, and IT consulting services, including the Slauth.io IAM Policy Copilot.

Open source · Self-hostable

Measures quantum-decryption risk to sensitive data with its Decryption Blast Radius score.

Open source

AI-powered bot protection and fraud prevention for websites and mobile applications.

Open source

GeeTest provides advanced bot management and detection solutions for real-time risk assessment and adaptive security.

Open source

AI agent management platform for securing and controlling AI agents, APIs, and events.

Open source

A one-time password (OTP) verification solution using a miscall-based system for enhanced security and cost-efficiency.

Open source

An autonomous AI that turns scammers into unwilling intelligence sources. Presented at Black Hat USA 2026.

Open source

Provides real-time fraud prevention and IP reputation services to detect and mitigate online abuse.

Open source

Forter provides an AI-powered trust platform for digital commerce, preventing fraud and abuse while maximizing revenue.

Open source

OpenAI is an AI research and deployment company dedicated to ensuring that artificial general intelligence benefits all of humanity.

Open source

Customer identity and access management platform for developers and enterprises.

Open source

Secure, identity-based connectivity platform replacing VPNs, SASE, and PAM for modern teams and workloads.

Open source

The enterprise features layer for developers.

Open source

Developer-first security platform providing continuous AI-driven penetration testing and vulnerability remediation.

Open source

Blockchain security and auditing firm providing smart contract auditing, KYC, and security tools.

Open source

Real-time threat intelligence platform.

Open source

Cloud-based browser API for AI agents, simplifying web automation with anti-bot protection and session persistence.

Open source · Self-hostable

Secures cloud environments by protecting human and non-human identities with a machine-first approach.

Open source

Agentic endpoint security for AI coding, providing visibility, governance, and real-time protection.

Open source

AI-native defense platform for software development.

Open source

AI-powered platform for building and managing customer-facing applications and workflows.

Open source

Developer-first platform for building secure, frictionless authentication and user journeys.

Open source

Piiano provides developer infrastructure for data protection and compliance, helping companies prevent data breaches and exfiltration at the code level.

Open source

An abstraction layer unifying cloud infrastructure and application code into a single programming and operational model.

Open source · Self-hostable

Monitors and remediates issues with third-party APIs, focusing on breaking changes, latency, and costs.

Open source

Ping Identity provides intelligent identity and access management solutions for enterprises.

Open source

Automated API security testing to proactively identify and eliminate complex application security risks.

Open source

Open-source, AI-driven endpoint investigation tool for security teams.

Open source · Self-hostable

Open-source platform for managing secrets and sensitive data for developers.

Open source · Self-hostable

Full-stack permissions as a service for developers, simplifying authorization management.

Open source

ForgeRock provides identity and access management solutions for enterprises to secure digital identities and manage access.

Open source

Torch Security provides universal identity security and governance for all identities, including non-human ones like AI agents.

Open source

The secure action layer for production AI agents.

Open source

Mobile app security and API protection platform for preventing fraud and abuse.

Open source

AI-powered platform for automated vulnerability discovery and remediation.

Open source

Develops an AI agent utilizing the Model Context Protocol (MCP) for enhanced AI interaction.

Open source

TandemTrace provides AI Threat Hunting Agents that weaponize LLMs for autonomous cybersecurity defense.

Open source

Formal verification and runtime monitoring for software and smart contracts.

Open source

Secures agentic AI communications and infrastructure with an end-to-end platform.

Open source

Paart inspects AI agent traffic to classify identities and enforce policy inline.

Open source

A mobile and web application development platform acquired by Google.

Open source

A global leader in cybersecurity and digital risk management solutions, protecting organizations from evolving threats.

Open source

Next-gen API security for semantic applications and LLMs.

Open source · Self-hostable

NetNut provided a residential and mobile proxy network and data scraping solutions for web data collection.

Open source

GitHub's suite of security tools for code scanning, secret detection, and dependency review.

Open source

AI-powered cybersecurity solutions for enhanced data protection.

Open source

Authentication and user management platform for React developers.

Open source

Aemetis is a renewable fuels and biochemicals company focused on low-carbon solutions like RNG and SAF.

Open source · Self-hostable

Decentralized authentication solution.

Open source

Independent defensive security research focused on detection engineering, threat analysis, and open-source tooling for defenders.

Open source

Bunsy provides a web frontend with authentication, protected pages, and NestJS integration.

Open source

AI-powered cybersecurity platform for cloud-native applications and infrastructure.

Open source

AI-powered vulnerability intelligence platform for proactive cybersecurity.

Open source

GitHub App for automating Python dependency security by detecting vulnerable dependencies.

Open source

Seamless and secure website verification for businesses, enhancing online trust and security. Launching soon!

Open source

AI-powered platform for trust and safety in digital interactions.

Open source