Authentication & Registration Best Practices: From Sign-Up to Account Recovery

A great product can still fail at the login screen. Long registration forms, weak security, and frustrating password recovery are some of the fastest ways to drive users away. Fortunately, building a secure authentication system doesn't have to come at the expense of a smooth user experience.

Key Takeaways:

• Keep registration simple to maximize user conversion and retention.
• Balance strong security with a frictionless user experience using MFA, passkeys, biometrics, and SSO.
• Authentication verifies identity; authorization defines permissions.
• Make account recovery secure and easy with email verification codes, backup codes, and well-designed recovery flows, improving both security and UX.
• Protect authentication systems against common threats such as brute-force attacks, account enumeration, and compromised passwords with layered security measures.
• Balance usability and security based on your application's risk profile, rather than prioritizing one over the other.
• Accelerate development with proven authentication solutions.

In this article, we'll walk through the entire authentication journey - from registration and sign-in to account recovery and security best practices - so you can create an experience users trust and enjoy.

First Impressions start at sign-up

A potential customer downloads your application and wants to jump right in. However, they see a humongous registration form that requires a ton of irrelevant information. They finally get in, but they cannot make the account more secure, as there is no multi-factor authentication. They also notice that they better not forget the password, as account recovery is very poor and requires users to contact customer support directly. And there it is – one more customer lost.

Smooth registration, seamless login, and secure account management are paramount when creating an application. In today’s piece, I will discuss these aspects in relation to app development and how you can ensure implementation is as efficient as possible.

This used to be simple back in the days when the signup process consisted of an email and a password. With the abundance of new verification methods using biometrics, passkeys, two-factor-authentication methods, and external authentication methods (SSO with Google, Apple, Meta, etc.), this universe has become more complex and confusing. In this article, we aim to clarify authentication and registration and showcase best practices for managing these processes. 

Planning a mobile app? Before discovering more on authentication, download our Checklist of High-Impact Features in Mobile Apps to make sure you're not overlooking the features users expect.

Designing a registration flow that converts

The first stop on this journey is registration. This is where the user lands when they don’t have an account yet.

This is where the user needs to provide the necessary information, such as the email address or password they wish to use to log in. They might also need to agree to your site's Terms and Conditions.

There are numerous ways to go about registering:

• Traditional Form: a classic form where the user provides all the information manually.
• Social Logins: by using existing accounts, users can register by connecting to a social platform like Facebook/Meta, Apple, or Google instead of providing their password.
• Phone Number: by using their phone number, the user can register by inputting a verification code instead of using email and password.
• Passkeys: a secure, passwordless solution that uses public cryptography and solutions such as biometric authentication.

This is what a registration form could look like:

Option 1:

Option 2:

How to secure new user accounts

The user is registered but wants to ensure their account has an extra layer of security. What can you do to help them?

The best way to ensure that your users’ accounts are well protected is to enable multi-factor authentication, also known as MFA. The aim is to establish a secondary (or tertiary) factor that makes it exponentially harder for a potential bad actor to get access to the user’s account.

It combines two of the following three things: something you know (such as a password), something you have (such as your physical device), or something you are (such as biometrics).

Want to extend your knowledge in this area? Read our article on Two-Factor Authentication (2FA): Strengthen Your App Security, where we explain authentication factors, implementation approaches, industry examples, and common security pitfalls.

What are KYB and KYC?

If your app handles finances, high-risk transactions, or otherwise uses highly sensitive data, you might want to implement KYB/KYC within your application. So, what do these terms mean?

KYC (Know Your Customer): verifying the identities of individual users to prevent fraud, comply with regulations (e.g., AML), and build trust. Documents that help to identify the user could include a driver’s license, a passport, or their ID.

KYB (Know Your Business): in order to verify the legitimacy of a business, especially in a B2B context, you might need to run a verification process that might involve authorized representatives, a registration form, or a VAT number.

To streamline the process, you might want to use automated KYB/KYC solutions to reduce manual effort. Requesting additional verification itself might be bothersome, but we ought not to compromise on security. Thankfully, we can make up for it by making it as user-friendly as possible.

OAuth2 and OpenID Connect: streamlining third-party access

Third-Party Access refers to granting external applications access to a user's account on another platform.  This allows users to use their existing accounts to access different services without having to create new credentials for each one.

Single Sign-On (SSO), which is enabled by OAuth2 and OpenID Connect, is commonly used for:

• Social Logins: registration and login using previously existing Google, Apple, or Meta accounts.
• Accessing Services: using your Google Account to access resources like third-party email clients.
• Sharing Data: granting access to data like fitness/health data.

Industry Guidelines: Major players like Apple and Google are increasingly requiring or encouraging third-party access via their platforms in their developer guidelines.
Apple: Link to relevant Apple developer documentation on using Sign in with Apple

Google: Link to Google's documentation on using OAuth 2.0 for accessing Google APIs

OAuth2 allows users to grant limited access to their own data on another platform without directly sharing the credentials. It enables solutions such as ‘Sign in with Google’.

OpenID Connect (OIDC) builds upon OAuth and provides user identity information to the application. This enables a more seamless and personalized user experience.

Admittedly, while third-party access offers a ton of convenience, it also carries potential risks, such as additional attack vectors.

For example, hackers gained access to Target systems using the credentials of a third-party vendor, ultimately compromising the payment card information of 40 million customers. A key quote that should really resonate is the following: ‘[...]customers no longer had faith in their security. After the data breach, customers were worried that their data would be leaked’.

Creating a frictionless login experience

Once users have registered, the next step is logging back into your application. While email and password are still common, modern apps often offer faster and more secure alternatives, such as social logins, passkeys, or biometric authentication. But choosing a login method is only part of the equation - you also need to decide what users can access once they're signed in.

Example:

Authentication vs. Authorization: what's the difference?

A big part of app login infrastructure is not only ensuring that only your users have access to what’s inside, but also that the right people have the appropriate privileges. You wouldn’t want anyone and everyone who is logged in to be able to perform admin changes!

And here we come across a commonly confused pair of keywords: Authentication and Authorization.

Authentication verifies who the user is, confirming that the person trying to enter is indeed your registered user. In this case, the 'who' refers to characteristics such as their name, e-mail address, etc.

On the other hand, authorization determines what a user can do once they're logged in – such as deleting other accounts or seeing sales data. You can define these access levels based on user roles, ensuring that the right people have access to the right data or can perform certain actions.

Choosing the right authentication method

There are numerous ways of tackling the abovementioned authentication. How exactly could we ensure that the person logging in is a registered user?

• Multi-Factor Authentication (MFA): It adds an extra layer of security by requesting a different type of verification altogether, such as biometrics or a code sent to the device.
• Biometrics: Allowing users to enable biometrics makes it both secure and super convenient. Face ID is a very popular solution in this sphere.
• Passkeys: A passwordless authentication method that uses cryptographic keys. This improves security and the user experience. Read our article on Passkeys to learn how they work and how to implement them.
• Magic Link/OTP: Sending a unique link or one-time password (OTP) to the user's email or phone number provides a simple, secure login option. This method can also be utilized in password resets.
• Phone Number Login: While not the safest option available, users can log in by using their phone number and an appropriate newly sent code.

Account recovery and user account management

Our user has now registered, logged in, and even set up their preferred authentication method. However, there’s more to account management than that! We need to set up a process that provides a clear, easy-to-use path to reset forgotten passwords or regain access to their accounts. This is crucial to maintaining a positive user experience.

Let’s walk through a couple of examples of how a user could regain access to their account, which would include the following:

1. Email-Based Reset: the user can reset their password by going into their inbox and using a one-time code that’s valid for a certain time. There are two main ways of doing it:

• Email verification with a CODE: This is the standard that is to be followed.
• Email verification with a LINK: Susceptible to scanning mechanisms that would automatically click the links and therefore render them expired.

Example:

2. Security Questions: While it should be considered an anti-pattern, users can choose security questions during registration. Then, if they forget the password, answering them would verify their identity. However, this is a major vulnerability if answers can easily be guessed or otherwise obtained.

3. Backup Codes: Generated during registration, backup codes can be used to reset their second factor of verification.

Example:

4. Support Contact: For complex cases, users can contact customer support to request assistance with account recovery. This should involve a secure verification process to protect user accounts.

Common authentication security risks (and how to prevent them)

It is clear how faulty security can affect your business, your service, and most crucially, your customers. Let’s take a look at some concrete examples of cybersecurity issues you should prevent when implementing your own system.

• Account Enumeration: Prevent attackers from guessing valid usernames or email addresses by implementing appropriate security measures.
• Password Security (MD5, Password Complexity, HIBP): Avoid outdated hashing algorithms like MD5. Enforce strong password complexity rules and integrate with services like Have I Been Pwned (HIBP) to check for compromised passwords. Educate users about password best practices.
• Brute-Force Attacks: Implement rate limiting and account lockout mechanisms to prevent attackers from repeatedly trying different passwords.

There are even more examples of how security can be compromised.

A convenient solution to tackle these issues without endangering the service by trying to work around them on your own would be to choose an out-of-the-box, battle-proven framework that’s both very safe and cost-efficient for your organization.

Balancing security and user experience

It has to be said that when it comes to security and UX, there’s always a tradeoff. The more secure you want the process to be, the more likely it is that you’ll require the user to jump through more loops to get authorized, which makes the barrier much higher for a potential bad actor, but naturally, it’s also a high barrier for that user.

On the flip side, though, if you make the process super easy, where you log in with your phone number and that’s it, it might be quick for the user, but it’s likewise quick for a hacker to get in.

Depending on the industry and the type of information you’re handling, you’ll need to maintain a careful balance between these two crucial aspects of your authorization process. Users’ level of tolerance for complexity is much higher when they deal with banking apps, but it’s the exact opposite for sport and fitness apps.

One example of a great middle ground, or even the best of both worlds, are passkeys, which I’ve mentioned numerous times throughout this piece. They are more secure than passwords while also being more user-friendly, making the authorization process seamless.

Authentication and registration best practices

Let’s take a look at a short summary of some of the best practices to adhere to when it comes to authorization.

• Registration Form Design: Keeping forms simple and easy to understand, while requesting the minimum amount of information, is highly recommended. An overly long registration process can deter users.
• Input Validation: Remember to implement a real-time validation of the input in the appropriate field to immediately catch errors and prevent frustration stemming from redoing the same form; for instance, make sure that the height can only be a number (or even narrow it down to between 100 and 250 cm) or that salary expectations cannot include words.
• Confirmation: Provide instant feedback to the user indicating whether an operation was successful. It is one thing to redo the form, but another to at least know that you need to do so rather than repeatedly clicking the `Submit` button.
• Principle of Least Privilege: grant users only the privileges they need. Create appropriate roles so that users cannot perform actions like an admin would, for instance.
• Defense in Depth: Implement multiple layers of security controls to protect your systems.  This approach ensures that if one security measure fails, others are in place to prevent or mitigate an attack.
• Rate Limiting: You can limit the number of login attempts from a given IP address by implementing rate limiting. This prevents brute force attacks.
• Strong Password Policies: Implement password complexity requirements to encourage users to adopt stronger account protections. This could include dictating the password length or the presence of special characters.
  

Authentication is just one piece of a successful mobile app. If you're planning a new product, our Checklist of High-Impact Features in Mobile Apps covers the other essential features worth considering before development begins.

Should you build or buy your authentication system?

Now that we know all the best practices and flows, there’s only one question remaining: where do we start implementing them?

There are two main options: a custom solution and a ready-made out-of-the-box solution.

1. Custom integration

This would require all the steps that you might expect, ranging from custom UI and accessibility to backend integration to testing and debugging.

2. Using ready-made out-of-the-box solutions

This approach is much more time- and capital-efficient, as you can use pre-created, battle-tested templates. Here at LeanCode, we take full advantage of Kratos, an authentication tool from Ory. We’ve combined it with our open-sourced framework, Core Library, which has enabled us to have ready-made solutions at our fingertips.

If you wanted to implement all the best practices and key flows presented in this piece, it could take months of development. If you'd rather avoid building authentication from scratch, our Flutter Mobile App Template solution includes production-ready authentication, authorization, and other essential app features, helping you ship faster while following proven best practices.

Conclusion

A great authentication flow doesn't just protect your users - it shapes their first impression of your product. By balancing security with usability and following proven best practices, you can build an experience that users trust from sign-up to account recovery.

If you're looking to accelerate development, explore our Flutter Mobile App Template, which includes production-ready authentication and other essential building blocks. And if you're planning a new mobile app, don't miss our Checklist of High-Impact Features in Mobile Apps to make sure you're building the features users expect.