> ## Documentation Index
> Fetch the complete documentation index at: https://confidence.spotify.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Segments

> A segment is a reusable audience definition, such as a cohort of users, that you use across flag rules and experiments instead of redefining the same targeting.

A segment is a definition of a subpopulation, like a certain cohort of users. Define it once and reuse it across multiple flags and experiments, so your targeting stays consistent and you don't redefine the same criteria each time.

<Note>
  A segment has no targeting key. Use segments with all targeting keys.
</Note>

## Segment Components

Segments consist of:

* **Inclusion criteria**: Filters that describe which users belong to the segment
* **Allocation**: The percentage of users matching the criteria to include
* **Exclusivity**: Optional setting to make segments mutually exclusive

These components follow the shared [audience targeting](/docs/capabilities/segments/audience) model that flags and experiments also use.

## Concepts

* [Materialized Segments](/docs/capabilities/segments/materialized-segments): Segments that load their list of units from BigQuery.
* [Audience Targeting](/docs/capabilities/segments/audience): Inclusion criteria, allocation, randomization, sticky assignment, and exclusivity for rules, experiments, and segments.

## Tasks

* [Create Segments](/docs/capabilities/segments/create-segments): Create a segment to define a reusable group of users.
* [Define the Audience](/docs/capabilities/segments/define-audience-criteria): Add inclusion criteria to target specific users in rules and segments.
* [Create Materialized Segment](/docs/capabilities/segments/create-materialized-segment): Create a materialized segment that loads units from BigQuery.
* [Launch an A/B Test](/docs/guides/run-an-ab-test): Target segments in experiments.