Google's Firebase is an entire app development platform that's packed with features.It comes with storage, cloud functions, monitoring and, of course, user authentication. The free tier comes with 50,000 MAUs. Beyond that pricing start at $0.0055/MAU and goes down to as low as $0.0025/MAU as you scale to millions of users. Firebase authentication supports email and password auth, phone auth, magic links, two-factor authentication and social identity providers - mainly Google, Google Play Games, Facebook, Apple, Microsoft, Twitter, GitHub and OAuth access tokens.

Auth0 is Okta's B2C identity management solution. It's an all-in-one package, with social login, bot detection, UI components, anonymous users, single-sign-on, MFA etc. The free tier comes with 7,500 MAUs. That said, it's relatively expensive and 20,000 MAUs will cost you $1400/month.

Clerk is a comprehensive authentication and user management platform. It comes with embeddable UIs, APIs and admin dashboards for user management. Clerk offers official SDKs for Next.js, React, JavaScript, Node.js, Remix, Go, Gatsby, and Ruby / Rails. There are many more community SDKs for other frameworks and languages. They have a free tier of 10,000 MAUs and a $25/month Pro tier with $0.02/MAU. Enhanced authentication, with SMS auth, device tracking and revocation, simultaneous sessions and SAML authentication costs additional $100/month. Admin add-on, with user impersonation and enhanced roles is another $100/month.

Supabase is the open-source alternative to Firebase. Like Firebase, it's a complete app development platform with user authentication, cloud functions, APIs, Postgres database, storage, vector embeddings, and other features. Supabase projects come with PostgreSQL's policy engine for fine-grained user access rules. It has social login integrations with Google, Facebook, GitHub, Azure (Microsoft), Gitlab, Twitter, Discord, and many more. They offer a customizable authentication component for React. Phone login and MFA can be added through third-party SMS providers such as Twilio or Bird. The free tier comes with 50,000 monthly active users. The Pro plan, at $25/month, comes with 100,000 MAUs and $0.00325/MAU beyond that.

They market themselves as the leading Auth0 alternative. There is a free starter plan with up to 25 organizations and 1000 members. Additional users costs $0.05 per monthly active user.

Kinde has a generous free plan with up to 10,500 MAU free of charge. Their Pro plan costs $25/month and the price for each additional MAU over 10,500 is $0.0175.

Appwrite is an open-source platform for building scalable applications. It comes with authentication, databases, storage, and functions. It's basically a complete development platform. They have an extremely generous free plan with 75,000 MAUs free of charge and their Pro plan is only $15/month. Appwrite offers email and password login, phone auth, magic links, email OTP, anonymous login, JWT login, SSR login, custom tokens, and two-factor authentication.

Formerly known as NextAuth. It's is an open-source authentication library originally built for NextJS. Auth.js is free to use and comes with over 80 integrations for various third-party identity providers such as Google, Facebook, Auth0, Apple etc. You can use it with your own database if you choose to. It works with MySQL, Postgres, MSSQL and MongoDB. Auth.js is compatible with Next.js, SvelteKit and SolidStart as of March 2024.

Keycloak is an open source identity and access management solution. It supports Keycloak single-sign-on and OpenID Connect or SAML 2.0 Identity Providers (Google, Facebook, GitHub etc).

Gluu offers various authentication solutions based on open-source software. There is a self-hosted solution, a managed solution, and a free fully open-source solution based on the Linux Foundation Janssen Project.

Okta is an identity provider for organizations. It offers enterprise solutions for managing workforce and employee identities. It's HIPAA BAA and PCI compliant.

Lucia is an open source auth library that abstracts away the complexity of handling sessions. It works with any JS runtime - Node.js, Bun, Deno, Cloudflare Workers. It's also fully typed. It integrates with MongoDB. PostgreSQL, MySQL, SQLite, and with their respective ORMs and query builders.

GoPasswordless is an authentication service and SDK that focuses on enabling passwordless authentication flows in web apps.

Authenticate customers with WhatsApp, SMS, Email, Biometrics, and more, with a 98% conversion rate on signup and sign-in.

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Owlbot offers a cutting-edge AI-powered chatbot service that seamlessly integrates with your data to provide instant responses for you, your customers, or your team. Deploying a tailor-made AI chatbot with Owlbot is straightforward, enhancing both customer service and the efficiency of data analysis with minimal effort. Our AI chatbot is capable of handling 90% of inquiries from customers, clients, or employees effortlessly (>90 languages supported). It can import data from a variety of sources, including documents, markdown files, and webpages, ensuring that you receive precise, immediate answers. Additionally, you can connect the chatbot to your internal tools to access private data in real-time and provide timely responses. You can choose from 12 different large language models (LLMs), such as Mistral, OpenAI, and Anthropic, to find the option that best fits your needs. Owlbot also captures the details of interested visitors, helping you compile a list of potential leads and expand your business opportunities.

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Instant credit system integration for Apps and Games with Creduse API. Simplify credit management for your application or game with our developer-friendly API solution. Enjoy quick integration, robust scalability, and comprehensive support, plus powerful analytics to monitor user activity.