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Feature flags

A brief history

Deploying feature and deploying code is generally associated as being one operation. When developpers want to add something to a website or an app, they add code.

From this assumption, people have improved the way they manage their code and created workflows that facilitate the deployment of their apps. One common example is the Gitflow. When using Gitflow, only the commits that exist on the main branch are deployed to production.

While this kind of flow make sense in some situation, we can question the strong link between deploying code and deploying features. Do we really need to couple the notion of deploying code to production and to rollout new features to the audience?

Separating the notions

It’s not necessary to couple code deployments and feature releases.

For instance, in trunk base development, you deploy code as soon as you can. Deploying so often means that the production application contains code for features that are not finished yet. Obviously the audience should not have access to something that does not properly work.

How to prevent your audience from accessing unfinished features? using feature flags.

A feature flag is basically a toggle: an on/off button. When on on, the user will see the new feature. When on off, they won’t.

In a codebase, it’s as simple as a condition:

const flags = useFlags();
if (flags.newDashboard) {
return <div>New dashboard</div>
return <div>Old dashboard</div>

From this simple concept of showing a feature based on a condition, it’s possible to create an interesting toolkit: under which constraints should the flag show the new dashboard? To how many user?

Features available in Progressively

  • Toggle features in one click
  • Single variant feature flag (e.g: true or false)
  • Multi variants feature flags (e.g: Control, A, B, you name it)
  • Flag activation based on date & time (before the, after the, always)
  • Progressively rollout (from 0% to 100% of the target audience)
  • Attribute based targeting (you provide a couple fields/value and can restrict flag evaluation for these couples)
  • Webhooks triggering on flag toggle
  • Insights on variants evaluated by your audience over time
  • Real time update with websockets (opt-in) in the JS sdk
  • SSR SDK for frameworks like Remix, Nextjs etc…