Segments

A segment is a named, reusable set of targeting rules. Instead of copy-pasting the same conditions into every flag ("email ends with @yourcompany.com"), you define the audience once and reference it by key. Update the segment in one place and every flag that uses it updates too.

Defining a segment

Segments live per environment and have a key, a human-readable name, an optional description, and a list of rules (the same rule shape flags use):

{
  "key": "internal-employees",
  "name": "Internal employees",
  "description": "Anyone on a company email",
  "rules": [
    { "attribute": "email", "operator": "ends_with", "values": ["@yourcompany.com"] }
  ]
}

Manage them in the dashboard's Segments page, or via the REST API (GET/POST/PATCH/DELETE /api/environments/{env_id}/segments). Creating or editing requires the editor or admin role.

Referencing a segment from a flag

In a flag's rule list, use segment_key instead of an inline attribute/operator/values:

{
  "key": "ai-assistant",
  "is_enabled": true,
  "rollout_percentage": 5,
  "rules": [
    { "segment_key": "internal-employees" }
  ]
}

You can mix segment references and inline rules freely, and a flag can reference multiple segments. Rules are still evaluated in order, first match wins.

How it works

• Server-side expansion. Before a flag is broadcast to SDKs (over SSE or the /flags/snapshot poll), the server replaces each segment_key reference with the segment's concrete rules. SDKs never see segments — they evaluate a plain, fully-expanded rule list, so there is zero SDK-side complexity or version coupling.
• Automatic re-broadcast. Editing or deleting a segment re-expands and re-publishes every flag that references it, so the audience change lands everywhere immediately.
• Variant propagation. A rule that references a segment_key can also carry a variant. That variant is applied to any of the segment's rules that don't already specify their own — so you can reuse an audience but return a different value per flag.

When to use a segment vs. an inline rule

Use a segment when…	Use an inline rule when…
The same audience is targeted by many flags	The condition is specific to one flag
The audience definition may change over time	The rule is a one-off
You want a single source of truth for "who is internal / beta / VIP"	You're prototyping a quick rollout

See also

• Core Concepts → Targeting Rules — operators and rule semantics.
• API Reference → Segments — the CRUD endpoints.