Feature Flag

Conversion & UX

Also: Feature Toggle · Feature Switch

What it doesTurns features on or off without a new deploy

Pairs withA/B testing and rollout control

Watch forFlag debt piling up unused

Used byProduct and engineering, not just marketing

Quick definition

A feature flag is a setting in code that lets a team turn a feature on or off, or show it to some users but not others, without releasing new code. It's the switch that decides who sees what, and when, after the code is already live.

What it actually means

A feature flag works like a light switch built into a feature before it's finished. Engineers wire the switch in while building, then flip it on for a small group, watch what happens, and flip it off again if something breaks. No new deploy needed either way.

This matters for conversion work because it decouples releasing code from releasing a feature. A checkout redesign can sit dormant in production, tested internally, then switched on for ten percent of users through segmentation while the rest see the old version. That's effectively an A/B testing setup, except the infrastructure is engineering-owned rather than marketing-owned.

Marketers usually meet feature flags secondhand, through a product team explaining why a landing page change is 'behind a flag' or why a call-to-action test can't launch until the flag is configured. Understanding the concept helps marketers ask better questions of engineering rather than treating flags as a mysterious blocker.

The risk is flag debt. Flags left in code long after their purpose expires make the codebase harder to reason about and can quietly re-enable old behaviour during unrelated changes.

A feature flag is a light switch wired into your codebase. The wiring is the hard part, not the flipping.

How it shows up

Feature flags show up whenever a product team says a change is 'gated', 'behind a flag' or 'rolling out gradually'. They show up in staged rollouts where a new checkout flow reaches five percent of users this week and fifty percent next week. They also show up in incident reviews, where the fastest fix for a broken feature is flipping its flag off rather than shipping a rollback.

Where people get this wrong

Assuming a feature flag and an A/B test are the same thing.A flag is the plumbing that controls exposure. A/B testing is the statistical method for judging what happened once exposure is split. You need the flag to run the test, but the flag alone tells you nothing about performance.

Leaving old flags in the codebase indefinitely.Unused flags accumulate as technical debt and create hidden risk, since a forgotten flag can re-enable retired behaviour during an unrelated code change.

Treating a flagged rollout as done once it's turned on.A feature behind a flag still needs monitoring, conversion tracking and a clear decision point for full rollout or rollback. Flipping the switch is the start of measurement, not the end of the project.

Common questions

Is a feature flag the same as an A/B test?

No. A feature flag is the mechanism that controls who sees a feature. An A/B testing setup uses flags to split an audience, then applies statistics to judge which version performed better. The flag enables the test but doesn't measure anything itself.

Why would marketing care about feature flags?

Because most staged landing page changes, checkout redesigns and new call-to-action placements ship behind flags. Understanding the concept helps marketers plan launch timing and ask engineering for gradual rollouts instead of all-or-nothing releases.

What is flag debt?

Flag debt is the build-up of feature flags left in code after their original purpose has ended. Each one adds a hidden branch of logic. Over time this makes the codebase harder to test and can cause old behaviour to resurface unexpectedly.

Can feature flags be used outside of engineering teams?

Some platforms give marketing or product teams a dashboard to flip flags themselves without touching code. This is common for controlling rollout percentage on user experience changes, but the flag still has to be built into the code by engineering first.

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About New Rebellion

New Rebellion is a marketing intelligence consultancy. We build tools, score Australian businesses on how their marketing actually performs, and publish Debrief every day. This dictionary is part of how we work in the open.

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