Top Castle alternatives

Clerk

Clerk is an authentication and user management platform for web apps, providing tools for secure login, session management, and user data handling.

UAE PASS

UAE PASS is a national digital identity app for accessing online services, signing documents, and managing official records securely in the UAE.

Persona

Persona is an identity management platform that automates user information verification and fraud detection for businesses.

Auth Armor

Auth Armor is a secure authentication platform using biometrics for easy, passwordless login and enhanced user identity management across applications.

Auth0

Auth0 is an identity and access management platform that simplifies user authentication and authorization for various applications.

Authsignal

Authsignal is an authentication platform offering passkeys and passwordless solutions for secure customer identity verification and fraud mitigation.

Privy

The Privy app provides secure digital signatures and digital ID solutions for businesses in Indonesia, enabling legal online transactions and identity verification.

IPQS

IPQS provides an API suite for detecting and preventing fraud, including bots and fake data, by validating digital identities in real-time.

Passage by 1Password

Passage by 1Password enables passwordless sign-in using passkeys for apps and websites, simplifying authentication integration and enhancing security.

Dynamic

Dynamic is a multi-chain wallet authentication and authorization platform that provides a user-friendly login experience.

LoginID

LoginID is an authentication platform that provides passwordless, biometric solutions for secure login across various industries, enhancing user experience and security.

ID.me

ID.me is a digital identity verification app that securely authenticates users' identities for various services, preventing fraud and ensuring compliance with standards.

Cloudflare Zero Trust

Cloudflare Zero Trust enforces access controls using a Zero Trust model, integrating with identity providers to secure application access and network traffic.

Memberstack

Memberstack integrates user authentication and payment processing into websites, allowing for secure membership management and customization in Webflow projects.

Okta

Okta is an identity management platform that secures user access to applications and resources through single sign-on and multi-factor authentication.

Stytch

Stytch is an identity platform providing secure, passwordless authentication solutions for developers, including SDKs for easy integration in web and mobile apps.

Userfront

Userfront is an authentication platform that simplifies user login and management for applications, supporting customizable flows and secure access across multiple platforms.

Yoti

Yoti is a digital identity app that securely stores personal information and facilitates age verification using biometrics and document checks.

Cloaking.House

Cloud service that cloaks landing pages and filters ad traffic to block bots, moderators, proxies, and unwanted clicks, routing legitimate users to offers; ML-based detection and simple integration.

WhatsAuth

WhatAuth is a secure OTP solution using WhatsApp for authentication tasks like login, password recovery, and transaction verification, offering a cost-effective alternative to SMS.

GPT Auth

The GPT Auth app allows users to customize their GPTs with no-code actions, enabling connections to any API for data management.

Youverse

Youverse allows users to manage accounts and authenticate identity using facial recognition without disclosing biometrics or requiring passwords.

SuperTokens

SuperTokens is an open-source user authentication solution that simplifies secure login processes for web and mobile applications.

AuthSmith

AuthSmith provides authentication and access control for apps: email/password, social sign‑in, SSO, MFA, role-based access, activity analytics, alerts, API integrations, and encrypted user data.

Clever

Clever provides a single sign-on portal for K–12 schools, allowing quick and secure access to educational resources for students and teachers.

Tesseral

Tesseral is an open-source platform for managing authentication and authorization in B2B software, allowing developers to handle user identities securely and efficiently.

FACEIO

FACEIO is a facial recognition SDK for secure, passwordless authentication on websites and apps, enabling face detection and identification.

Cloudflare Turnstile

Cloudflare Turnstile is a CAPTCHA alternative that prevents spam and confirms user authenticity without compromising privacy or user experience.

NoFraud

NoFraud is an app that provides real-time fraud detection for eCommerce, protecting businesses from fraudulent transactions and enhancing the checkout experience for customers.

FusionAuth

FusionAuth is an identity and access management platform that offers secure authentication and authorization features for applications.