Feature Toggle (Or Flipper): What Is It and Why Use It?

Written by: Drew Piland
11 min read

After clicking the final merge pull request button of the day, you sit back in your chair. Tomorrow signals the release to all customers. The development team has dedicated themselves to make it outstanding, yet a sense of unease lingers in your gut like a weighty stone.

Big-bang releases can be intimidating, often causing restless nights for weeks as issues arise post-launch. You've contemplated the remedy - feature toggles - a technique lauded by your fellow developers. However, delving into this strategy has escaped you due to time constraints.

This post provides a concise read to enlighten you. Pause to uncover the essence of feature toggles, the change they bring, and the benefits of a robust toggle management system.

Feature Toggles (aka Feature Flags)

Features are patterns that enable the organization to deliver new features in a timely, safe manner. Feature Toggling is an interactive tool that starts with an introduction to the basics. We'll then go deep into detail, revealing particular techniques and patterns to ensure successful use of feature-oriented toggles for teams. Features Toggles can be referred to in the same terms as Features Flag - Bit Flip - Feature. It is a combination of different techniques. The toggle and flag feature are referred to in this blog post interchangeably.

What Is a Feature Toggle?

In its simplest form, a feature toggle is a conditional statement that controls whether the code for a specific feature will be executed.



// execute new code




// execute old code


Feature toggles are also known as feature toggles, feature flags, and feature bits. They all serve the same purpose and are used interchangeably.

What are the advantages of feature toggles?

Features are able to experiment with new features without worrying about release too quickly which allows developers to experiment. There will be no return if something fails in testing phase.

Feature Toggles Explained: Essential Terms for Effective Implementation

When you start using feature toggles, it’s good to be aware of some terminology.

  • toggle point is a point where code execution branches in one direction or the other: the conditional statement in the code above.

  • A toggle router is a function that decides whether a feature is enabled or disabled. Unlike the example above, you want to use toggle routers at your toggle points because you want the decision logic in a single place.

  • When the values a toggle router used to make its decision come from outside, you use toggle configuration. For example, a configuration file or a system setting or an environment variable.

  • When the data used by a toggle router is specific to a group of users or even a single request, that data is your toggle context.

Feature toggle development process

The first step in establishing and executing feature toggles is creating and specifying it on an outside data source. Typically the user must select an initial name or key in the toggle feature or choose an additional status. Upon setting the toggle feature, application and infrastructure can see its status through an identifier with its own key. If a toggle is created within Optimizely or other applications, the toggle must have a visible state. So code needs to be incorporated into the codebase to enable an application to view status on a feature toggle in an external source.

Maximize Success: Leveraging Feature Toggles for Effective Software Development

This feature flag helps mitigate potential issues with changes in applications and improves user experience. With any major change, the risk is that new regressions will be released. For reducing this, changes to an application could be placed behind toggles to permit their turn "on" and "on off" when a problem occurs. In more complex cases, toggle is useful for testing changes in smaller groups of people. By setting feature toggles in certain groups, the teams gain insight before changes can be implemented across the entire organization.

Boost Development Efficiency by Leveraging Feature Toggles for Enhanced Collaboration

Say farewell to feature branch merge issues by utilizing feature toggles. With trunk-based development, everyone can collaborate seamlessly without the need for feature branches. By defaulting feature toggles to disabled, prevent any active feature codes when unnecessary. Optimize speed and performance by incorporating feature toggles in your development process.

Because feature-activating toggles enable rapid deployment and rollback of new code, they can help support the trunk development process by allowing code changes in trunk rather than having multiple feature branches which need to be merged and reconciled on Github. Thus release cycle speeds can be improved.

Enhance Your New Feature with Feature Toggles for Confident Development

To ensure the effectiveness of your new feature, activate its feature toggle. You can commit changes confidently, even to the trunk, before it's accessible to others. Regularly committing small updates helps speed up feedback cycles for better results.

Optimize Continuous Deployment Success with Trunk-Based Development and Feature Flags for Improved Results

The trunk-based development enabled by feature flags means the trunk is always in a releasable state. That means you can have continuous integration, delivery, and deployment to production. And that, in turn, means that releasing code and releasing features are no longer joined at the hip, and you get to test in production.

What is the purpose of canary release and feature toggles?

Canary releases allow development tools to be incrementally tested by a small audience. Features provide an alternative way to perform canary launches.

Canary Releases and Champagne Strategies for Feature Rollouts

You can use toggle configuration and toggle context to be selective about which customers get to use a new feature. This allows you to see how a feature is received and is holding up before rolling it out further.

With a canary releases, you randomly select a percentage of users. It’s perfect if you want to monitor performance issues and unforeseen glitches. With a champagne brunch, you select specific people. It is perfect to dogfood your own app to get early feedback from internal users (alpha testing), as well as to run large opt-in beta tests.

Experiments to Avoid Hippos

Feature flags are a valuable tool for experimentation in software development. By creating multiple simple implementations for different ideas, teams can efficiently determine which performs best and resonates with users. This method enables teams to prioritize features by analyzing user behavior and feedback, optimizing the product development process.

Using feature flags to run A/B testing experiments means you no longer have to guess. Because you now use trunk-based development and test in production, you get to gather data from real live users and get to make data-driven decisions. That data will go a long way to change any HiPPO (highest paid person’s opinion) in the room.

Enhance Product Development: The Power of User Feedback and Feature Flags

Striving for perfection can hinder progress. Without feedback from actual users, it's challenging to anticipate their preferences for new features and usability. Attempting to perfect a product by catering to every possible need can lead to inefficiencies.

Utilizing feature flags enables the delivery of the most valuable features to users promptly, allowing for feedback that drives updates and enhancements continuously. This iterative process not only accelerates development through small, incremental changes but also avoids wasting resources on unused features.

Embracing this approach not only enhances development speed but also ensures that efforts are focused on features that users will benefit from, ultimately optimizing the user experience.

Simplify Software Management

When launching a new feature, unforeseen negative impacts can occur despite thorough testing. Simplify management with feature toggles - the ultimate kill switch solution for your software!

Enticingly Advanced Features

Feature flags empower marketers and sales teams to attract customers by offering enhanced features for premium access.

Graceful Degradation

Kill switches can be used when your systems experience an unusually high load. Disabling features that are expensive in terms of resources and performance can allow your app to continue its essential function.

When and how are feature flags applied?

In practice features already formulated can often go undeveloped because it's impossible to implement them productively. It is likely they'll have no flags for this branch. Thanks to Feature Toggles / Flags, finalized code is instantly merged and deployed to make the new feature available in background. The change also helps prevent major problems when merging later if other parts were being worked on.

The Downsides of Feature Toggles: Pitfalls You Can't Ignore

By now you may think that feature toggles sound too good to be true and there must be a catch. And you’d be right. Feature flags have a few pitfalls you want to avoid.


Using feature toggles increases the complexity of your code, and for each toggle, you need to run your tests twice: once with the toggle disabled and once enabled. However, it’s not as bad as it sounds. Feature flags rarely influence each other, so you don’t have to test every possible combination. And if you release features often, each release will only touch a limited number of feature flags.

Test Cycle Duration

To ensure efficient testing, consider restarting or redeploying to test environments if toggle configuration adjustments can't be made at runtime. This practice can help streamline the testing process, enhancing developer productivity and development speed.

Testing in production

Due to the complexity of modern deployable systems, it is possible for test environments in the production environment and in the testing process to contain bugs. By adding features toggling in the development process software developers are capable of launching features in the Production Environment in control of a smaller segment of their audience for less risks and allowing for testing new features on production machines. Using a toggle configuration that has no modifications in source code will automatically roll back the test if it fails.

Multiplying Feature Toggles

Feature toggles, or feature flags, are widely used in software development and can spread quickly across a codebase. However, unmonitored toggles may result in an abundance of complex conditional logic, leading to code readability challenges. This tangled toggle scenario can hinder codebase comprehension and maintenance, impacting development speed.

It Can Still Be Too Good to Knock It

The advantages of feature toggles far outweigh the drawbacks. Plus, you can easily mitigate these by being proactive in keeping your feature toggles under control. Proactively removing toggles that are no longer necessary, for example.

Still, to get the full benefits of feature toggles, you need a good system to manage them. Not only to keep track of them, but also to:

  • Manage who can change a feature toggle’s state. For example, allowing marketing and salespeople to determine which (types of) customers get to use a feature. Or allowing product managers to play with toggles for A/B testing.

  • Give operations people control of the kill switches they need to keep your app running with limited features, rather than it crashing altogether.

  • Offer a good, simple user interface that non-techies can safely use.

  • Integrate with your CI/CD server.

Of course, you can build and grow your own toggle management system. At first, that will seem like the obvious thing to do. Soon, however, working on it will be taking precious time and effort away from the product you want to and should be working on: the product your customers pay for.

That’s why it makes total sense to take advantage of a product that’s someone else’s core business, so you can concentrate on yours.


In summary, implementing feature toggles can revolutionize your software development process. By embracing this powerful tool, you can streamline feature releases, gather real-time user feedback, and pave the way for continuous improvement. Despite potential complexities, the benefits of feature toggles far outweigh the drawbacks. Remember, with proper management and proactive measures, you can harness the full potential of feature toggles to enhance your software development journey. So, why wait? Start toggling your way to success today!

Time to Get Your Hands Dirty

Now, to reduce anxiety and improve sleep, it's crucial to understand what's needed for a smoother new release experience.

What's the next step? I suggest delving into best practices and practical application. Nothing beats hands-on practice to truly grasp your newfound knowledge.

A highly effective approach is to kick off with a small project, implementing feature toggles for a real-world feel: introducing new features, addressing bugs, experimenting with canary releases and A/B testing, and celebrating achievements along the way.

While at it, explore CloudBees' feature flag management system to enhance your understanding. By combining these actions, you'll gain insights into nurturing your projects and the advantages of adopting a solution from an expert company.

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