Segments

Target your experiment to a specific subset of visitors.

What is a segment?

A segment is a set of rules that filters which visitors are eligible for an experiment. Only visitors matching the segment will be bucketed — everyone else sees the default experience.

Use cases:

• Test a change only on mobile visitors
• Run a campaign-specific experiment for paid traffic (utm_source = google)
• Test a new landing page only for visitors from a specific referrer

Creating a segment

Go to Segments → New segment and define your rules. Rules can be combined with AND or OR logic.

Available fields

Field	Values	Evaluated
device	mobile, tablet, desktop	Client-side (window width)
utmSource	Any string	Client-side (URL param)
utmMedium	Any string	Client-side (URL param)
utmCampaign	Any string	Client-side (URL param)
referrer	Any string	Client-side (document.referrer)

Operators

Operator	Meaning
eq	Exactly equals
neq	Does not equal
contains	String contains

Assigning a segment to an experiment

On the experiment Overview tab, use the Segment dropdown to assign a saved segment. You can change this at any time, even on a running experiment.

Client-side evaluation

Segment rules are evaluated in the browser before any bucketing happens. Fields like device, utmSource, and referrer are available immediately. Server-side fields (country, customer type) are not yet supported — rules with unknown fields default to allowing the visitor through.

Device detection uses window.innerWidth at script execution time: < 768px = mobile, < 1024px = tablet, ≥ 1024px = desktop.