Conditions

Conditions are the conditional logic primitive that powers segments and message overrides. They describe how runtime context, feature flags, and experiments determine whether a piece of authored content applies.

Condition kinds#

There are three kinds of conditions:

Attribute conditions check a value from runtime context against an expected value with an operator.
Feature conditions check whether a feature flag is enabled via an application-provided resolver.
Experiment conditions check whether an experiment variation matches via an application-provided resolver.

Attribute conditions are native to Messagevisor. Feature and experiment conditions activate only when your application registers a resolveFlag or resolveVariation function on the SDK instance, typically through a module that integrates with a feature management tool like Featurevisor.

Attribute condition#

conditions:
  - attribute: plan
    operator: equals
    value: pro

attribute is the key of an authored attribute, or a dot-notation path into a nested object attribute (account.country).
operator is one of the operators listed under Operators reference.
value is the expected value. Its type depends on the attribute and operator; some operators (exists, notExists) take no value.

Feature condition#

conditions:
  - feature: new-checkout
    operator: isEnabled

feature is the feature flag key.
operator is isEnabled or isDisabled.

If no resolveFlag is registered on the SDK instance, the condition evaluates to false.

Experiment condition#

conditions:
  - experiment: checkout-copy
    operator: hasVariation
    value: bold

experiment is the experiment key.
operator is hasVariation.
value is the variation name that should match.

If no resolveVariation is registered on the SDK instance, the condition evaluates to false.

Condition shapes#

conditions can be authored in several equivalent shapes depending on how much structure you need.

Single condition#

A single condition object:

conditions:
  attribute: plan
  operator: equals
  value: pro

Array of conditions#

An array of conditions is treated as an and by default. All children must match.

conditions:
  - attribute: age
    operator: greaterThanOrEquals
    value: 18
  - attribute: plan
    operator: equals
    value: pro

Logical groups#

Use and, or, and not for explicit grouping.

AND#

conditions:
  and:
    - attribute: plan
      operator: equals
      value: pro
    - attribute: platform
      operator: in
      value:
        - web
        - ios

OR#

conditions:
  or:
    - attribute: plan
      operator: equals
      value: enterprise
    - and:
        - attribute: plan
          operator: equals
          value: pro
        - attribute: signupDate
          operator: before
          value: "2026-01-01T00:00:00Z"

NOT#

not matches when its child group does not fully match (i.e. it negates an and):

conditions:
  not:
    - attribute: country
      operator: equals
      value: us

You can nest and, or, and not to any depth.

Wildcard#

Use the literal string "*" to always match. This is useful for "everyone" segments or unconditional overrides:

segments/everyone.yml

description: Everyone
conditions: "*"

Operators reference#

All supported operators at a glance:

Operator	Type of attribute	Description
`equals`	any	Exact match
`notEquals`	any	Does not match
`exists`		Attribute is present and not null
`notExists`		Attribute is missing or null
`greaterThan`	`integer`, `double`	Strictly greater
`greaterThanOrEquals`	`integer`, `double`	Greater than or equal
`lessThan`	`integer`, `double`	Strictly less
`lessThanOrEquals`	`integer`, `double`	Less than or equal
`contains`	`string`	Value contains the substring
`notContains`	`string`	Value does not contain the substring
`startsWith`	`string`	Value starts with the string
`endsWith`	`string`	Value ends with the string
`before`	`string`, `date`	Date is before the given one
`after`	`string`, `date`	Date is after the given one
`includes`	`array`	Array attribute contains the value
`notIncludes`	`array`	Array attribute does not contain it
`in`	`string`	Attribute value is in the array
`notIn`	`string`	Attribute value is not in the array
`isEnabled`		Feature flag is enabled
`isDisabled`		Feature flag is not enabled
`hasVariation`		Experiment variation matches

Examples for each operator below.

`equals`#

conditions:
  - attribute: country
    operator: equals
    value: NL

`notEquals`#

conditions:
  - attribute: country
    operator: notEquals
    value: NL

`exists`#

conditions:
  - attribute: country
    operator: exists

`notExists`#

conditions:
  - attribute: country
    operator: notExists

`greaterThan`#

conditions:
  - attribute: age
    operator: greaterThan
    value: 21

`greaterThanOrEquals`#

conditions:
  - attribute: age
    operator: greaterThanOrEquals
    value: 18

`lessThan`#

conditions:
  - attribute: age
    operator: lessThan
    value: 65

`lessThanOrEquals`#

conditions:
  - attribute: age
    operator: lessThanOrEquals
    value: 64

`contains`#

conditions:
  - attribute: name
    operator: contains
    value: John

`notContains`#

conditions:
  - attribute: name
    operator: notContains
    value: Smith

`startsWith`#

conditions:
  - attribute: name
    operator: startsWith
    value: John

`endsWith`#

conditions:
  - attribute: email
    operator: endsWith
    value: "@example.com"

`before`#

Both sides are interpreted as dates. Use ISO 8601 strings for authored values.

conditions:
  - attribute: signupDate
    operator: before
    value: "2024-01-01T00:00:00Z"

`after`#

conditions:
  - attribute: signupDate
    operator: after
    value: "2024-01-01T00:00:00Z"

`includes`#

includes applies when the attribute itself is an array:

conditions:
  - attribute: permissions
    operator: includes
    value: write

`notIncludes`#

conditions:
  - attribute: permissions
    operator: notIncludes
    value: write

`in`#

in applies when the value is an array and the attribute is a single value:

conditions:
  - attribute: country
    operator: in
    value:
      - be
      - nl
      - lu

`notIn`#

conditions:
  - attribute: country
    operator: notIn
    value:
      - fr
      - gb
      - de

`isEnabled`#

Requires a resolveFlag function registered on the SDK instance. Evaluates to false when no resolver is available.

conditions:
  - feature: new-checkout
    operator: isEnabled

`isDisabled`#

Requires a resolveFlag function registered on the SDK instance. Evaluates to false when no resolver is available.

conditions:
  - feature: new-checkout
    operator: isDisabled

`hasVariation`#

Requires a resolveVariation function registered on the SDK instance. Evaluates to false when no resolver is available.

conditions:
  - experiment: checkout-copy
    operator: hasVariation
    value: bold

Where conditions are used#

In segments#

A segment names a reusable conditional building block by wrapping conditions with a description and an optional archived/promotable flag:

segments/plan-pro.yml

description: Pro plan users
conditions:
  - attribute: plan
    operator: equals
    value: pro

Inline on a message override#

A message override can use conditions directly when the logic is small and specific to that message:

messages/auth/signin.yml

overrides:
  - key: platform-web
    conditions:
      - attribute: platform
        operator: equals
        value: web
    translations:
      en: Sign in from browser

Overrides can also reference segments via segments: instead of conditions:. Segments are themselves built from conditions, so the underlying authoring vocabulary is the same.

Attribute access#

The attribute field names an authored attribute. When the attribute is of type object, you can read a nested field with dot notation:

conditions:
  - attribute: account.country
    operator: equals
    value: NL

Each dot-separated segment is a property lookup. If any intermediate property is missing, the value is treated as missing, which makes exists evaluate to false, notExists evaluate to true, and any other operator evaluate to false.

Examples#

A single condition that targets web users:

conditions:
  - attribute: platform
    operator: equals
    value: web

The same logic used inside a segment:

segments/platform-web.yml

description: Target web users
conditions:
  - attribute: platform
    operator: equals
    value: web

And inline on a message override:

messages/auth/signin.yml

description: Sign in button label
translations:
  en: Sign in
overrides:
  - key: platform-web
    conditions:
      - attribute: platform
        operator: equals
        value: web
    translations:
      en: Sign in from browser

Edge cases and behavior notes#

An array of conditions is implicitly AND#

conditions as an array means all of them must match. Use or explicitly when any of them should be sufficient.

`not` negates an AND of its children#

{ not: [a, b] } matches when a and b do not both match. It is not a per-child negation. Use nested not if you need that.

Missing attribute paths short-circuit#

If an attribute path is missing on the runtime context, every comparison operator returns false. The only operators that treat "missing" as a valid signal are exists and notExists.

Feature and experiment conditions need application wiring#

Without resolveFlag or resolveVariation registered on the SDK instance, isEnabled, isDisabled, and hasVariation always evaluate to false. This is intentional, since Messagevisor does not assume which feature flag system you use.

Linting catches authoring mistakes#

When attributes are defined, linting validates that referenced attribute keys and value types match. This catches typos and type mismatches before runtime.

Target context can simplify conditions at build time#

When a target declares partially known context, the builder can determine whether a condition is always true, always false, or still variable. Impossible branches are removed from the built datafile. See Targets for the details.

Condition kinds#

Attribute condition#

Feature condition#

Experiment condition#

Condition shapes#

Single condition#

Array of conditions#

Logical groups#

AND#

OR#

NOT#

Wildcard#

Operators reference#

equals#

notEquals#

exists#

notExists#

greaterThan#

greaterThanOrEquals#

lessThan#

lessThanOrEquals#

contains#

notContains#

startsWith#

endsWith#

before#

after#

includes#

notIncludes#

in#

notIn#

isEnabled#

isDisabled#

hasVariation#