Overrides

Overrides let a message serve different translations to different audiences at runtime, based on context, segments, attributes, and optional feature or experiment integrations.

Basic structure#

An override lives inside a message's overrides array. Each override has:

key: a unique stable identifier within the message
one of segments or conditions (or both)
translations: the alternate locale-to-string map

messages/auth/installApp.yml

translations:
  en: Install the app
  nl: Installeer de app
overrides:
  - key: platform-ios
    segments: platform-ios
    translations:
      en: Download on the App Store
      nl: Download in de App Store
  - key: platform-android
    segments: platform-android
    translations:
      en: Get it on Google Play
      nl: Download via Google Play

Override keys#

Every override must have a unique key within the message. The key:

is used for merging during sets-based promotion
appears in CSV export rows with the format messageKey:overrideKey
is required before a message can participate in promote

overrides:
  - key: plan-pro          # stable identifier
    segments: plan-pro
    translations:
      en: Your Pro workspace is ready

Segment-based overrides#

Reference a named segment when the condition is reusable across multiple messages.

overrides:
  - key: mobile
    segments: platform-mobile
    translations:
      en: Download the app

Use logical groups with and, or, or not to compose multiple segments:

overrides:
  - key: dutch-web
    segments:
      and:
        - dutch-account
        - platform-web
    translations:
      en: Your Dutch workspace is ready
      nl: Je Nederlandse werkruimte staat klaar

The wildcard * matches all users:

overrides:
  - key: universal
    segments: "*"
    translations:
      en: Special message for everyone

Condition-based overrides#

Use conditions directly on an override when the logic is specific to one message and not worth extracting into a named segment.

Single inline condition:

overrides:
  - key: pro-user
    conditions:
      attribute: plan
      operator: equals
      value: pro
    translations:
      en: Your Pro plan is active

Compound condition with and:

overrides:
  - key: adult-mobile
    conditions:
      and:
        - attribute: age
          operator: greaterThanOrEquals
          value: 18
        - attribute: platform
          operator: equals
          value: mobile
    translations:
      en: Adult mobile content

Feature and experiment conditions#

Attribute conditions and segments work with Messagevisor context directly. Overrides can also reference feature flags and experiment variations when your SDK or module setup provides resolvers, for example from a Featurevisor integration:

overrides:
  - key: faster-checkout
    conditions:
      and:
        - feature: new-checkout
          operator: isEnabled
        - experiment: checkout-copy
          operator: hasVariation
          value: bold
    translations:
      en: Try the faster checkout
  - key: classic-checkout
    conditions:
      feature: new-checkout
      operator: isDisabled
    translations:
      en: Your classic checkout is ready

Available feature/experiment operators:

isEnabled / isDisabled: based on a feature flag
hasVariation: based on the active experiment variation

Without resolvers, prefer modeling audience data as Attributes in the Messagevisor context.

Condition operators reference#

Attribute conditions support these operators:

Operator	Value type	Notes
`equals`	any
`notEquals`	any
`exists`	none	attribute is present in context
`notExists`	none	attribute is absent from context
`greaterThan`	number
`greaterThanOrEquals`	number
`lessThan`	number
`lessThanOrEquals`	number
`contains`	string	substring match
`notContains`	string
`startsWith`	string
`endsWith`	string
`before`	date string	date comparison
`after`	date string	date comparison
`includes`	string	value is in an array attribute
`notIncludes`	string
`in`	array of values	attribute is in the list
`notIn`	array of values

Override evaluation order#

Messagevisor evaluates overrides top-to-bottom and returns the first matching override.

That means:

order matters
more specific overrides should appear before more general ones
changing order can change runtime behavior

Override translations and locale inheritance#

Each override has its own translations map, and locale inheritance applies to override translations too.

If en-US inherits from en via inheritTranslationsFrom: en, the override translation for en will be inherited by en-US unless en-US has an explicit override translation.

Description and summary on overrides#

Overrides also accept description and summary fields for documentation purposes:

overrides:
  - key: mobile
    description: Shorter copy shown on narrow mobile screens
    summary: Mobile variant
    segments: platform-mobile
    translations:
      en: Contact us

These appear in CSV exports and in the catalog.

Overrides and build#

During build, the builder:

reads all overrides for each message
evaluates target context against conditions and segments
keeps only the overrides that remain reachable for the target's known context
includes only the segments and attributes used by surviving overrides

This means the runtime datafile can have fewer overrides than the authored source. That is intentional: target context eliminates impossible branches ahead of runtime.

Overrides in CSV export#

When exporting to CSV, each override appears as a separate row. The message key column uses the format:

messageKey:overrideKey

For example, auth.installApp:platform-ios would appear as a row with its own translation columns.

The separator is configurable via exportOverrideKeySeparator in Configuration.

Overrides and promotions#

During promote, override arrays are merged by key. This means:

overrides from the source set are matched with overrides of the same key in the destination set
new override keys from the source are added to the destination
override keys that only exist in the destination are preserved

This merging behavior requires that all overrides have unique keys before promotion.

`promotable` on overrides#

Setting promotable: false on an override prevents it from being updated during promotion even if the message itself is promotable:

overrides:
  - key: environment-specific
    promotable: false
    segments: platform-web
    translations:
      en: Environment-specific text

Edge cases and behavior notes#

Conditions vs segments#

Use a named segment when the condition applies to more than one message. Use inline conditions when the logic is specific to one message and adding a segment file would just add noise.

Wildcard segments#

segments: "*" matches all users. This is useful when you want an override that always fires regardless of context, such as a temporary banner or one-time announcement.

The `*` wildcard for conditions#

You can also set conditions: "*" on an override. This behaves the same as segments: "*" - the override fires for all users.