Every consumer-facing app needs to answer the same unglamorous question: how do users sign up, sign in, and stay secure — without your team building authentication from scratch and getting it wrong? In 2026, if you are on AWS or Azure, the managed answers are AWS Cognito and Azure AD B2C (now part of Microsoft Entra External ID). Both are customer identity and access management (CIAM) services that handle registration, login, multi-factor authentication, social and federated sign-in, and token issuance, so you do not store passwords or implement OAuth flows yourself. They differ in pricing, customisation depth, developer experience and how they fit the wider cloud. This guide compares Cognito and Azure AD B2C across features, flexibility and cost, and shows which suits which kind of UK product team.
Choose AWS Cognito if you are building on AWS and want CIAM that drops straight into the AWS ecosystem (API Gateway, Lambda, AppSync) with generous free-tier usage and pay-as-you-grow pricing. Choose Azure AD B2C / Entra External ID if you are Microsoft-centric, need deep customisation of sign-up journeys, or want enterprise-grade identity governance alongside consumer sign-in. Both handle the security fundamentals well. Cognito tends to win on simplicity and AWS-native integration; Azure AD B2C wins on policy flexibility and fit for Microsoft estates and complex B2B/B2C blends.
The 2026 CIAM landscape
Customer identity has become a category of its own, separate from workforce identity, because consumer sign-in has different demands: massive scale, social logins, progressive profiling, branding, and friction-minimising flows. Alongside Cognito and Azure AD B2C, the market includes specialists like Auth0 (now owned by Okta) and Firebase Authentication, which many teams prefer for developer experience. But for organisations standardising on a single cloud, the native option avoids another vendor and another bill. Cognito gives you user pools (your own directory) and identity pools (federated access to AWS resources). Azure AD B2C gives you a dedicated consumer directory with highly customisable user journeys defined through policies, and Microsoft has been consolidating it under the Entra External ID brand with a more modern developer experience.
| Feature | AWS Cognito | Azure AD B2C / Entra External ID |
|---|---|---|
| Core concept | User pools + identity pools | Consumer directory + user flows |
| Social / federated login | Google, Apple, Facebook, SAML, OIDC | Google, Facebook, SAML, OIDC, more |
| Customisation | Lambda triggers, hosted UI | User flows + custom policies (XML) |
| MFA | SMS, TOTP, email | SMS, email, TOTP, conditional |
| Best ecosystem fit | AWS-native apps | Microsoft / mixed B2B+B2C |
| Pricing model | Per monthly active user, free tier | Per monthly active user, free tier |
Pick AWS Cognito if…
Pick Cognito if your application stack is on AWS and you want authentication that integrates with the rest of your serverless or container architecture with minimal glue. Cognito user pools plug directly into API Gateway authorizers, Lambda triggers (so you can customise sign-up, migration and token generation in code), and AppSync for GraphQL APIs. Identity pools let authenticated users assume IAM roles to access AWS resources directly — powerful for mobile and single-page apps that talk to S3 or DynamoDB. The hosted UI gives you a quick, brandable login page, and the generous free tier plus per-monthly-active-user pricing makes it economical to start. Cognito suits teams who value AWS-native simplicity and are happy customising through Lambda rather than a separate policy language.
Pick Azure AD B2C if…
Pick Azure AD B2C if you are Microsoft-centric, need very granular control over the sign-up and sign-in experience, or must blend consumer and business identity. Its user flows cover the common journeys out of the box, while custom policies (the Identity Experience Framework) let you orchestrate almost any multi-step, multi-provider journey you can describe — at the cost of a steeper learning curve. For UK enterprises that already run Entra ID for their workforce, extending into customer identity on the same platform keeps governance, security tooling and skills consistent. The move to Entra External ID also modernises the developer experience and brings consumer and partner (B2B) scenarios under one roof, which is attractive for organisations with mixed audiences.
Build the skills: recommended courses
Implementing CIAM well needs cloud platform knowledge, web/app development skills and a security mindset. Start with cloud fundamentals, add development depth, and layer security understanding on top.
Grounds you in IAM, the shared-responsibility model and the AWS services Cognito integrates with. Essential context before wiring authentication into a real AWS application.
Covers Entra ID and Azure’s identity model — the foundation Azure AD B2C builds on. The right first step for anyone implementing Microsoft customer identity.
CIAM is implemented in your app. This bootcamp builds the full-stack web skills — APIs, tokens, front-end flows — you need to integrate either Cognito or Azure AD B2C correctly.
Strong front-end fundamentals including React, which is where most login UIs and token handling actually live. A recognised credential for app developers implementing auth flows.
The security grounding that turns a working login into a secure one — covering authentication, common attacks and defensive practice that apply to any CIAM platform.
Common mistakes and real-world pitfalls
The biggest authentication mistakes are about security defaults and token handling, not the platform. Skipping multi-factor authentication, storing tokens insecurely in the browser, or failing to validate tokens server-side are perennial sources of breaches regardless of whether you use Cognito or Azure AD B2C. Treat MFA as default-on for anything sensitive, validate JWTs properly on every protected request, and use short-lived access tokens with refresh-token rotation. The second classic error is over-engineering the identity journey early — building elaborate custom policies before you have users — when a standard hosted flow would ship faster and serve fine.
Other recurring pitfalls: underestimating migration, since moving existing users into a new CIAM provider needs careful password-migration or just-in-time import handling; ignoring rate limits and bot protection on sign-up endpoints, which attackers probe relentlessly; neglecting branding and UX, because a clunky login page measurably hurts conversion; and forgetting compliance, since customer identity data falls squarely under GDPR — minimise what you collect, document consent, and honour deletion requests. Finally, teams often lock themselves in by scattering provider-specific logic throughout the app; isolating authentication behind a clean interface makes a future switch between Cognito, Azure AD B2C or a specialist like Auth0 far less painful.
Cost and scaling considerations
Both Cognito and Azure AD B2C price primarily on monthly active users (MAU) with a free tier that covers small applications comfortably, plus charges for extras like SMS-based MFA, which can become a surprising line item at scale because each text message costs money. The practical advice is to model your expected MAU growth and your MFA channel mix before committing: favouring TOTP authenticator apps or email over SMS can cut costs significantly as you grow, while also being more secure. Watch for tiered pricing thresholds where per-user costs change, and remember that advanced features (advanced security detection in Cognito, custom policies and premium Entra features in Azure) may carry separate charges. Pricing for both evolves regularly and Microsoft’s transition to Entra External ID has shifted some terms, so verify current rates for your region and projected scale rather than relying on older comparisons. As always, the cheapest CIAM is the one you configure securely the first time — a breach costs far more than any subscription tier.
Frequently asked questions
What is the difference between CIAM and workforce identity?
Workforce identity (like Entra ID or AWS IAM Identity Center) manages your employees’ access to internal systems. CIAM (Cognito, Azure AD B2C) manages your customers’ sign-up and sign-in to your products, at far larger scale and with consumer-focused features like social login and branding.
Is Cognito or Azure AD B2C easier to implement?
Cognito tends to be simpler for straightforward flows, especially within an AWS app, using the hosted UI and Lambda triggers. Azure AD B2C is more flexible but its custom policies have a steeper learning curve. For simple journeys both are quick; for complex orchestration Azure AD B2C offers more control.
How do they compare to Auth0 or Firebase?
Auth0 and Firebase Authentication are popular for developer experience and cloud-agnostic use. Cognito and Azure AD B2C win when you are committed to AWS or Azure and want to avoid an extra vendor. Many teams weigh developer experience against ecosystem fit and billing consolidation.
Do both support social and enterprise login?
Yes. Both support social providers (Google, Apple, Facebook) and enterprise federation via SAML and OpenID Connect, so you can offer consumer social logins and corporate single sign-on from the same service.
Which is cheaper?
Both price on monthly active users with a free tier, so cost depends on your scale and MFA channel mix. SMS-based MFA is a common hidden cost on both. Model your MAU and prefer app-based or email MFA over SMS to control spend, and check current regional pricing before committing.
Can I migrate users from one to the other later?
Yes, but plan for it. User migration requires handling password hashes (often via just-in-time migration on first login) and careful testing. Isolating authentication behind a clean interface in your app makes any future provider switch much less disruptive.