Define your audience once.
Target it everywhere.
Segments are reusable groups of users defined by attributes, identifiers, or custom criteria. Create "EU users" or "beta cohort" once — then reference them in any flag's targeting rules.
Example segments
EU users
country is one of: DE, FR, IT, ES, NL...
Beta cohort
userId is in list: [user_123, user_456...]
Paying customers
plan is one of: team, enterprise
Internal team
email ends with: @flaggy.io
Mobile users
platform is one of: ios, android
Power users
sessionCount is greater than: 50
How segments work
Attribute-based rules
Define membership by any attribute you pass in the evaluation context — country, plan, email, custom properties. String, number, boolean, and list comparisons all supported.
Explicit user lists
Add specific user IDs or identifiers to a segment. Useful for internal teams, design partners, or curated beta groups.
Reusable across flags
Create a segment once and reference it in as many flag targeting rules as you want. Update the segment definition and all flags using it update automatically.
Evaluated client-side
The SDK downloads your segment definitions along with flag rules. Segment membership is checked locally — no round-trip required at evaluation time.
Combine with rollout percentage
Target a segment and add a percentage rollout on top. For example: "10% of EU users" — the SDK handles consistent assignment within the segment.
Segment limits by plan
| Plan | Segments | Rules per segment |
|---|---|---|
| Free | 2 | Unlimited |
| Team | Unlimited | Unlimited |
Start targeting the right users
Free plan available. No credit card required.