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 an identity and access management (IAM) platform designed to simplify authentication and authorization for applications. It provides a flexible solution that allows developers to implement secure login systems without having to build them from the ground up. Auth0 supports various authentication methods, including username-password credentials, social logins (like Google, Facebook, and GitHub), enterprise identity providers (such as Active Directory and SAML-based systems), and passwordless options. The platform is highly adaptable, offering over 30 software development kits (SDKs) that cater to a wide range of languages and frameworks—JavaScript, Python, .NET, iOS, Android, and more. This makes integration straightforward regardless of the tech stack. Beyond basic authentication, Auth0 offers advanced features like multi-factor authentication (MFA), single sign-on (SSO), and fine-grained authorization. These tools enable organizations to enforce complex access control policies, supporting both role-based (RBAC) and attribute-based (ABAC) models. Auth0 also addresses enterprise needs through features like user provisioning, directory synchronization, and support for B2B, B2C, and B2E use cases. It’s designed with scalability in mind, making it suitable for both startups and large enterprises. The platform’s extensibility allows developers to customize authentication flows, implement rules for conditional access, and integrate third-party services. Since its acquisition by Okta, Auth0 operates as a product unit under the Okta umbrella, complementing Okta’s broader suite of identity solutions while maintaining a developer-first focus. This combination brings together Okta’s enterprise-grade security with Auth0’s developer-centric approach, offering a comprehensive solution for modern identity challenges.

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.

Stytch provides a suite of tools designed to simplify authentication, authorization, and security for web and mobile applications. If you're developing an app and need a way for users to log in—whether with passwords, passkeys, or entirely passwordless methods—Stytch offers APIs and SDKs that handle these complexities. Their focus is on making authentication seamless for both developers and end-users while ensuring high security standards. For businesses, particularly B2B SaaS companies, Stytch enables advanced features like multi-tenancy, role-based access control (RBAC), and single sign-on (SSO). They provide an embeddable admin portal, allowing enterprise customers to manage their own authentication configurations, organizational settings, and integrations with identity providers—without constant developer involvement. Stytch places a strong emphasis on scalability and flexibility. Their tools are designed to “just work” across a range of use cases, from simple consumer apps to complex enterprise platforms. Developers can choose how much of the authentication flow they want to control—using pre-built UI components for quick implementation or leveraging headless SDKs and backend APIs for a fully customized experience. Security and fraud prevention are also core to Stytch’s offering. They provide real-time bot detection, device-aware multi-factor authentication, and intelligent rate limiting to protect against credential stuffing and other forms of account abuse. Their infrastructure ensures that login codes and authentication requests are delivered reliably, even when SMS or email providers fail. Stytch supports a broad range of programming languages and frameworks, including Python, Node.js, Java, React, and iOS, making integration into existing tech stacks straightforward. Their platform is designed for developers who want to build secure, user-friendly authentication systems without reinventing the wheel.

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.

Ory is an API-first identity manager. They offer authentication, analytics, access control, machine-to-machine authentication and more. They have SDKs for the major languages: - Dart - .NET - Elixir - Go - Java - JavaScript - PHP - Python - Ruby - Rust Unfortunately, they don't offer a free tier. Pricing starts at $29/month and includes 1,000 daily active users. Then it's $30 / 1,000 additional DAUs.

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.

Clubistry is the easy solution for clubs seeking to make running a club as fun as being in a club. Effortlessly handle membership management, online payments, website building, and content management in one unified platform. Promote news and events, collect user info with custom forms, and process new membership applications online in a snap.

SaaSBoilerplates.dev is a curated directory that showcases a wide range of SaaS boilerplates, starter kits, and frameworks to help developers quickly launch their SaaS projects. The website features a carefully selected collection of tools and resources that cover various aspects of SaaS development, from authentication and payments to user management and deployment. Key Features 1. Extensive collection: SaaSBoilerplates.dev offers a comprehensive selection of SaaS boilerplates, catering to different frameworks, tech stacks, and development needs. 2. Curated by hand: The boilerplates are hand-picked and reviewed by a human to ensure quality, reliability, and relevance. No scraping, no AI-generated crap. 3. Detailed information: Each boilerplate listing includes a description, pricing, and key features to help readers make informed decisions. 4. Variety of use cases: The boilerplates cover a wide range of SaaS applications, including marketplaces, AI tools, landing pages, and more. Benefits 1. Time-saving: By leveraging pre-built boilerplates, developers can significantly reduce the time and effort required to set up the foundation of their SaaS project. 2. Cost-effective: Using boilerplates can help lower development costs by providing a solid starting point and reducing the need for custom development. 3. Scalability: Many boilerplates are designed with scalability in mind, making it easier to grow and expand the SaaS application as it gains traction. 4. Reduced technical debt: By using well-tested and maintained boilerplates, developers can minimise the risk of technical debt and ensure the long-term stability of their SaaS application. By leveraging the resources available on SaaSBoilerplates.dev, users can focus on building their core product features and bringing their SaaS ideas to life faster than ever before.

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.

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Scribbl is an AI meeting assistant that transforms conversations into searchable, shareable knowledge while you focus on what matters - the conversation. With smart summaries, instant video highlights, and seamless integrations, your meetings become actionable intelligence without the busy work. Key Features - Smart Transcription & Recording: Crystal-clear transcripts and video capture without intrusive bots or complicated setup - AI-Powered Summaries: Automatically extracts key topics, decisions, and action items from every conversation - Instant Navigation: Jump to any moment using AI-enhanced video search and topic breakdown - Team Intelligence: Automated sharing rules and collections ensure insights reach the right people - Business Tool Integration: Seamlessly syncs with HubSpot, Pipedrive, Slack, and Google Drive Benefits - Time Reclaimed: Stop taking manual notes and focus fully on your conversations - Perfect Memory: Never miss a detail with searchable transcripts and smart summaries - Effortless Documentation: Meeting insights automatically flow into your CRM and team tools - Enhanced Collaboration: Keep everyone aligned with intelligent sharing and organized collections - Client Success: Streamline follow-ups and ensure every client interaction is captured and actionable Use Case Use Scribbl to automatically capture, summarize, and distribute critical meeting insights across CRM and collaboration platforms. For example, A sales team uses Scribbl to automatically document client meetings, with notes flowing directly into HubSpot and key moments shared instantly with account managers. Team leads gain visibility through automated collections, while clients receive polished follow-ups faster - all without anyone taking manual notes.

Truelist is a subscription-based email verification platform that provides unlimited email validation for sales and marketing lists. It’s tailored for sales and marketing professionals as well as developers, offering one-click integrations with popular platforms to simplify list imports. With no need to purchase credits, teams can validate lists affordably and efficiently. Additionally, Truelist offers free single email validation, making it versatile for both bulk and individual verifications. By keeping lists clean, it boosts engagement and strengthens sender reputation, essential for effective email outreach.