Function flags finest practices. One-click management over what customers see

Think about that you just launch a brand new characteristic and fear about nothing – you’ll be able to flip it on and off in seconds, steadily roll out new parts, make A/B exams, configure conditional entry, and rather more. That magical resolution is characteristic flags. Feels like your life is about to get simpler? Sure, however keep in mind that with nice energy comes nice accountability. As we speak is your fortunate day, you’ll learn to profit from characteristic flags finest practices and tips on how to implement characteristic flags in your software program growth challenge.

What are characteristic flags and why do you want them?

Options flags (or characteristic toggles) are a mechanism that permits to allow or disable options (items of code) with out deploying a brand new model of the app. You management the visibility of a single characteristic and even complete pages within the app. 

From the developer’s perspective, the characteristic flag is an extra if assertion in code. The one distinction is that the circumstances are managed outdoors the app. 

That’s why I name characteristic flags “ifs as a service”.

particular feature flag (feature toggle) meme - no to add if to code, yes to add new feature flag

There are quite a lot of providers that enable you with characteristic flags administration however, after reviewing the out there choices, I extremely advocate LaunchDarkly. You should utilize LaunchDarkly in each internet and cell growth. This device means that you can set totally different values for a flag, share rollout, and a lot extra extra. I’m utilizing LaunchDarkly for over a 12 months now and I couldn’t be happier with it.

Function flagging finest practices on your utility

You determined that you just want a flag in your system and need to implement this accurately. Right here’s what it is advisable to deal with.  

Make investments time in good naming conventions

When working with characteristic flags it’s essential to speculate time in good naming. Individuals say that naming variables are one of many hardest issues in programming. With regular variables, you’ll be able to at all times test the file and different variables for context. However with characteristic flag naming is the one factor you need to work with. Relying on the title you need to know the aim of this flag. For instance: 

The extra particulars you present within the title, the higher. 

Don’t use disable/conceal in flag title

I don’t advocate utilizing detrimental kinds in if’s circumstances. It’s arduous to learn and requires extra effort to make use of. Like with this instance:

With one flag it’s nonetheless simple to decode the which means. However what if there’s multiple flag in situation? 

It’s also very irritating while you need to set a correct flag worth. Think about: “That is disabled after I give true worth, so to allow this on manufacturing I’ve to provide false worth”. False worth to allow flag is unintuitive.

single toggle critical path code change for certain code paths

Create staff naming conventions for flags

That is an extension of the earlier paragraph. Get a complete staff on board and write down conventions and requirements on your flags. Right here’s what you need to take into account:

  • including staff title to flag (it’s simpler to search out folks answerable for flags),
  • including a prefix to the flag title (e.g temp, rollout, experiment, config file, and so forth.) will simplify flag administration and take away outdated flags,
  • camelCase or snake_case,
  • different naming conventions that you just already use in your initiatives.

Describe flag function 

A very good title is a minimal requirement for the flag to be usable. However I extremely advocate including some description to the flag. That is data for you and different teammates about why this flag was created. It seems pointless while you create this, however consider me – after weeks/months/years you received’t keep in mind why you created this flag. Description may be added instantly within the software program you employ for flags, however you can too create an extra doc.

Create a doc for monitoring functions

It’s simple so as to add a brand new flag nevertheless it’s arduous to trace all of them. From my expertise, builders neglect about flags simply after ending their duties. Generally they’re reminded about the identical characteristic flags when a bug happens. And belief me after I say that eradicating the flag when nobody remembers why it was created within the first place is the worst job possible. Particularly when the flag creator doesn’t work within the firm anymore or the response product staff was remodeled into one other. 

remember about feature flags in code base & code deployment documentation

What data you need to observe:

  • flag title,
  • accountable staff,
  • ticket the place characteristic toggles had been launched (or the context why the flag was launched),
  • anticipated end-of-life date,
  • every other notes.

Make audits

Sadly, making a doc shouldn’t be sufficient. It is a wonderful follow to make common doc audits. I like to recommend at the very least one test per 12 months or each six months. Throughout this audit, you need to test if:

  • each flag is properly described,
  • each flag is on this doc,
  • you continue to want your short-term flags (temp, rollout, experiment),
  • pointless flags had been eliminated. 

Advantages of a characteristic flag applied into your app 

Function flags have a number of very encouraging benefits.

For my part, the perfect revenue is that characteristic flags separate code from visibility to the consumer.

Merging new options/enhancements to code doesn’t imply that each consumer will see this in-app. This manner you acquire full management over the characteristic lifecycle (together with characteristic visibility) and cut back the variety of crucial bugs on manufacturing

Let’s see extra characteristic flagging earnings in additional element.

Launch now, activate later

You don’t want extra branches for brand spanking new options and may merge adjustments in code (new options/enhancements) on to the primary department. This removes a lot of issues on the developer aspect:

  • you don’t should sync the characteristic department with the primary,
  • a brand new characteristic is at all times in sync with different adjustments,
  • no code conflicts,
  • simpler to make adjustments to the entire utility (e.g library updates),
  • all adjustments are small and code evaluation is fast.

There’s a pleasant upside from a enterprise perspective too. Builders can merge recently-added options after they suppose they’re prepared. Then a supervisor decides if the characteristic launch course of will occur now or if it wants to attend a bit longer for a greater alternative. For instance this instance: builders completed a brand new characteristic for a web based store nevertheless it’s every week earlier than Black Friday – a day of huge consumer visitors. Is it higher to introduce this characteristic earlier than or after Black Friday? Will it confuse the customers or make buying simpler for them?

Safety button

Function flags work as a safety swap – if there’s something fallacious with new performance, you’ll be able to disable it with one click on. 

You in all probability skilled testing new options. It’s an advanced course of and wishes a lot of expertise from the tester. Nonetheless, it doesn’t matter what you do, every so often you’ll omit a bug inflicting issues within the manufacturing surroundings. In a traditional workflow, recognizing an error on manufacturing means debugging. You then’ll spend a while fixing and deploying a brand new model. If it’s a crucial error for user-facing options, folks received’t be capable of use your app for a number of hours, inflicting loss to the enterprise. 

In the event you use characteristic flags as a substitute, you’ll be able to first disable a given characteristic, giving groups on a regular basis they should work on fixing this situation, and if obligatory, modify system conduct. Function flag administration may be very simple, and have switches take minutes, not hours. 

feature flag best practices. debugging by disabling permanent feature flags

Each new component in your app ought to bear thorough characteristic testing. Try how our QA staff offers with it: 

Conditional entry

Excellent for worldwide apps which have a consumer base from across the globe. Because of numerous circumstances (e.g. authorized points), customers in a single nation see totally different choices/options than in others. Due to the characteristic flag system you’ll management the visibility of given components of the app for particular circumstances like nation, language, foreign money, preferences, and so forth.

Distant configuration

That is barely much like conditional entry however has a special objective. Function flag may be greater than a boolean worth. It may also be different sorts, like strings and numbers used to create a distant configuration for the characteristic. Now you’ll be able to change configuration on the fly and redirect the customers to totally different options. 

Canary deployments

Canary deployment is without doubt one of the secure methods to deploy a brand new model of the app to customers. You roll out a brand new model to a small variety of customers and monitor if all the pieces is working properly. Steadily enhance the variety of customers till all the consumer base is moved to the brand new model. With a characteristic flag, you are able to do this with a single characteristic. You may configure what number of customers will see a sure characteristic. Use this as an prolonged High quality Assurance check to test the current characteristic earlier than you launch it to all customers.

A/B exams

The identical mechanism can be utilized for A/B exams – two variations of the identical characteristic/web page/message to see which works higher for the consumer. You should utilize characteristic flag share rollout to maneuver some customers to model A and the remaining to model B. Keep in mind to log which model customers see and what they do there. It’s essential to create a abstract after the experiment. After the tip date, you need to take away all experiment toggles. After creating the characteristic flags for A/B exams, I like to recommend including an extra ticket to take away the flags and transfer them to one of many future sprints.

The State of Frontend 2022 report is out now!
Learn it on-line or obtain a free copy📊👩‍💻

The report’s outcomes are based mostly on 3703 surveys crammed by frontend specialists on all ranges of proficiency, representing 125 international locations! 19 frontend consultants supplied their commentary to every topical part. It’s an actual deal with for anybody with a frontend background. See what applied sciences are nonetheless scorching, what lose their affect, and what rising stars we anticipate within the foreseeable future.

Disadvantages of characteristic flags 

All that glitters shouldn’t be gold! Function flags should not ducktape or WD40 that clear up all issues. Function toggling has its personal set of points that you need to take into account to keep away from characteristic flag hell. 


From a enterprise perspective, characteristic flags are very addictive. Now the managers don’t have to attend for builders to change options on and off, they’ll do it themselves. I’ve already stumbled upon managers who would love to regulate entry to mainly all the pieces utilizing characteristic flags. Extra management doesn’t essentially imply an excellent factor in the event that they lack technical information. Therefore, the function of builders is to make use of a characteristic flag solely when it’s wanted. In any other case, you’ll introduce a lot technical debt.

more feature flags is not always a good idea. Check if you have too many feature flags with developers.

Introducing technical debt

Do you keep in mind that the characteristic flag must be applied in code utilizing if statements? If statements at all times introduce debt as it is advisable to management it and supply default conduct. 

One other drawback is outdated, not used flags that had been applied up to now however should not obligatory anymore. In the event you don’t want these characteristic flags, simply delete them. Be very cautious to not create extra sophisticated ifs statements that use the identical flags as a result of eradicating them afterward will probably be more durable. 

manage feature flags makes sense. best practices for feature flagging system

Surprising dependencies

It’s simple to regulate code when you might have one flag. However after a while will probably be two characteristic flags and accumulate to dozen or tons of of various flags. You could know the connections between them so as to check them correctly. 

Think about that you need to allow 5 flags to the best values to get entry to a characteristic. Rising the variety of flags will result in extra consumer paths within the app. It’s a must to take note of all of them, or you’ll create a useless finish for the consumer.

Laborious to debug

Surprising dependencies make debugging rather more sophisticated as you need to know all flags state to breed bugs. A small change within the flag will trigger totally different outcomes. You could not solely have good utility monitoring applied to detect the place the consumer is having issues but additionally hold observe of what distinctive set of flags that specific consumer has enabled to repeat the bug and repair it accordingly.

release flags aka release toggle collect data for deploying code paths for user behavior

I can’t think about my work with out characteristic toggles anymore

I’ve been utilizing characteristic flags for over a 12 months now and I can’t think about creating superior initiatives with out them. I misplaced rely of what number of occasions characteristic flags saved us from crucial manufacturing errors with unimaginable testing pace. 

In the event you observe my ideas, including new options to customers will probably be simpler and fewer annoying, so I extremely advocate you test characteristic flags earlier than your subsequent manufacturing launch. 

The ultimate ideas: 

  • characteristic flags are good while you need to have management over whether or not to show new  performance or to not the tip consumer,
  • don’t add a characteristic flag routinely to each characteristic – add these solely when required,
  • make investments time in good naming conference and stick with it, 
  • NEVER use detrimental values to allow a flag, 
  • observe your characteristic flags, 
  • test every so often when you nonetheless want your short-term flags or you’ll be able to take away them,
  • be taught to say “No” when the product supervisor desires an pointless characteristic flag, 
  • keep in mind about logging details about flags when utilizing this characteristic.
Aleksander Patschek

Aleksander Patschek

Frontend Developer

JavaScript developer with three years of expertise. Massive fan of strongly typed languages that’s why he makes use of Typescript at any time when he can. Olek likes to be taught new frameworks, languages and options. In his free time, he reads fantasy books (Terry Pratchett’s “Discworld” FTW!), does sports activities and performs pc video games. Hearthstone, anybody?


Leave a Reply

    Your Cart
    Your cart is emptyReturn to Shop