Feature flags, also known as feature toggles, allows developers to enable or disable specific features in an application. They can do this without deploying new code. They act as conditional statements in the code that control whether certain functionality is accessible to users or hidden.
In its simplest form feature flags act as an on/off switch that can toggle a feature without developers having to do a release. But feature flags work better when they use extra information. This helps you decide whether to turn a feature on or off.
Feature flags are a modern development practice. They help improve the development process. They also benefit the product team and the entire business. Decoupling code releases from feature releases, instant rollbacks and A/B testing are some of the use cases
In this article, we will look at the benefits and use cases of feature flags. We will see how they improve team agility. We will also discuss the best practices for using them in your product.
A quick look at feature flags might make you think that it is very similar to a config file where you specify a bunch of keys and then use them to decide what features should be active in your app.
And if you are only looking to switch features on and off a config file that does not require application reload might do the job.
The thing that distinguishes features from config files is that you should be able to couple it with data that in turn decides if a feature should active. For example you can couple feature flags with application roles to decide who should have access to a feature. Another example would be that you only wish uses with a specific payment plan to have access to a feature.
On the other hand, config files store application settings that are necessary for its operation, such as database connections, API keys, environment variables, or other settings. They typically do not change the behavior of specific features but instead provide information that the application needs to run correctly in different environments (development, staging, production). Config files are usually static and updated only when deploying new versions of the application.
Feature flags decouple code deployment from feature releases by allowing developers to deploy new code without immediately making the associated features visible or accessible to users. Traditionally, releasing a new feature meant deploying the corresponding code directly into production, making it live for all users as soon as the deployment was complete. This created a strong link between code deployment and feature release.
Feature flags break this dependency by introducing conditional logic in the code that determines whether a feature should be active or hidden, independent of the deployment process. With feature flags, developers can deploy code containing unfinished, experimental, or partially implemented features without exposing them to users. The flag controls the feature, keeping it dormant until it's ready to be unveiled.
This separation is highly beneficial in continuous integration/continuous delivery (CI/CD) environments, where frequent deployments are common. You can gradually release features to select users (such as beta testers), monitor them for performance and bugs, and then fully launch them when the team feels confident. In case of issues, developers can quickly disable the feature without rolling back the entire deployment.
We call this “Soft launches” and it has been one of the most valued improvements in our development process. One main reason for this is that we could now move away from weekend and late night releases, a practice we used to de-risk downtime when users were active in the system. Another benefit was that our product managers could now plan the feature releases independently.
No matter how much we test on QA and staging environments all development teams have experienced bugs in the production environment and there is no way to avoid it. But with feature flags you can now reduce the impact by gradually releasing a feature out to your user base. Feature flags makes gradual releases aka incremental rollouts possible by allowing developers to control the scope of the release dynamically, adjusting who gets access to the feature at any given time.
In a gradual release, you initially roll out the feature to a small percentage of users, often starting with internal teams or beta testers. This limited exposure allows developers to monitor the feature's performance, gather feedback, and detect any potential bugs or issues. If the feature performs well, you can progressively make it available to more users, eventually reaching 100% of the user base. It also allows your product managers to test in production without any risk. This can be done by enabling the feature to only one account.
The advantage of this approach is that it minimises risk. If any problems arise during the rollout, developers can pause or roll back the release without affecting the entire user base. It also allows for real-world validation of the feature under varying conditions, leading to better performance and user experience.
Gradual releases improve control over the feature lifecycle, reduce the impact of unforeseen issues, and provide an opportunity for fine-tuning before a full launch.
Instant rollbacks is another way that feature flags reduces the risk in releases. By allowing developers to disable a problematic feature immediately without the need for a code deployment or rollback of the entire application. With feature flags, each feature is wrapped in conditional logic, which can be toggled on or off at runtime. This gives development teams real-time control over the feature's availability.
In traditional software deployments, rolling back a buggy or problematic feature often requires redeploying an earlier version of the application, which can be time-consuming and disruptive. It might involve stopping services, reversing database migrations, or affecting other components unintentionally.
With feature flags, if you detect an issue in a feature during or after a release, developers or even non-technical team members can instantly turn off the feature by toggling the flag. This rollback doesn’t require new code to be deployed or the application to restart; the change takes effect immediately. The underlying code stays in place but is simply hidden from users.
This ability to instantly disable a feature mitigates risk, ensures high availability, and enhances user experience by preventing extended downtime or the need for complex rollback processes. Feature flags provide a fast and non-intrusive way to react to issues in production.
Feature flags true shining power comes when you connect it with your user data.
This makes it possible for you to personalise and target features based on specific user attributes which enables a very flexible and tailored feature management. You will be able determine which users or groups have access to certain features.
Here’s some examples of what you can do:
Custom enterprise packaging: Since each flag represents a distinct feature. You can easily target a set of features towards a single client or even a user. This gives you a lot of flexibility towards enterprise customers that might not fit in your standard pricing tiers.
Targeted Feature Rollouts: You can roll out features to specific user segments, such as by geographic location, account type, user behaviour, or subscription level. This ensures that only the right users get access to certain features, helping you test new functionality in a controlled way.
Control feature by User roles : If you have different user roles with different privileges you can use this information to toggle different features or whole sections of your application.
Device specific features: Certain features may only be relevant or functional on specific devices. For example, a hardware specific feature might only work on your smartphone but be irrelevant for your desktop users. With feature flags, you can ensure that only the appropriate device users have access to these features.
Feature flags are a powerful tool for A/B testing because they make it possible for product owners & product managers to dynamically control which users see specific features or variations of features in real time. A/B testing involves showing different groups of users two or more versions of a feature (Version A and Version B) to evaluate which one performs better based on predefined metrics, such as user engagement, conversion rates, or overall satisfaction.
Here’s how feature flags enhance A/B testing:
Feature flags are a powerful tool for managing pricing tiers in a SaaS product, particularly when you need flexibility in defining and adjusting feature sets or usage limits. Here's a few examples on how feature flags can be utilised for SaaS pricing packages:
Feature flags are incredibly useful for launching and managing beta programs in software development. Beta programs allow you to release a new feature or version of your product to a select group of users before making it available to the entire user base. Here’s how feature flags enhance the beta testing process:
As your product grows, so does the complexity of managing features and the user groups accessing them. Feature flags offer a flexible way to control which features are enabled for different user segments, but without a clear naming convention, things can quickly get confusing. A clear feature flag naming convention will provide a structured approach that ensures feature flags remain easy to understand for all stakeholders, from developers to product owners, marketing, and sales teams.
let’s explore some best practices for naming feature flags, so we maintain flexibility and scalability as the number for flags grow
One of the most important principles in feature flag naming is to keep the feature flag name focused on the functionality being toggled and user segments separate. This separation ensures that your feature flag names remain flexible even when user groups or segments change. For example:
Tying a feature name to a specific user segment (like “admin users”) makes it difficult to modify the group later. Always name the flag after the feature itself and use user segments to determine the scope of access.
Your feature flags should clearly describe the feature they control, without referencing specific user groups or conditions. A well-named flag, like enable_new_dashboard, makes it obvious what functionality is being toggled, even to non-technical teams. This is key for communication between developers and stakeholders, allowing everyone to understand the feature's purpose at a glance.
User segments should reflect the specific groups or roles accessing a feature. These segments define who the flag applies to, so their naming should clearly describe either the role, pricing tier, or other attributes being evaluated. For example:
This separation allows the same feature flag to be used across multiple user groups, enhancing the flexibility and modularity of your flag system.
As features evolve, it’s common to have multiple versions live at the same time. Including version numbers in your flag names helps you track different iterations. For instance, you might have feature_new_ui_v1 and feature_new_ui_v2, each representing a different stage of your feature rollout. Versioning avoids confusion when teams are dealing with multiple iterations of the same feature.
In larger projects, prefixing feature flags based on the type of functionality they control can make it easier to manage them. Common prefixes might include:
This approach allows you to categorize your feature flags, making them easier to filter and manage as your project scales.
The way you implement feature flags depends on the specific use cases you have in mind. Different scenarios require varying levels of complexity in the implementation.
Let’s consider a few common use cases:
When thinking about how to implement these, it becomes clear that each use case demands its own logic with differing levels of complexity.
For example, if you only need to decouple code deployments from feature releases, the required logic is straightforward: you just need to enable or disable a feature. This isn’t too complex, and you could likely code it yourself.
However, for use cases like soft launches, A/B testing, or beta testing, the complexity increases. You would need to write code to gradually roll out the feature to more users, define user groups based on demographics or other parameters, and handle dynamic user segmentation.
Additionally, if you want to free up developers’ time, a user interface (UI) that allows non-technical team members to manage feature flags is a big advantage.
When your needs go beyond simple feature toggling, or when freeing up developer resources becomes a priority, it’s worth considering an external feature flag management tool or service.