Use flow variables

A flow variable is a named value the flow looks up once and then uses in messages, conditions and webhook requests. Examples: a coupon code constant, the user's city, or today's opening index fetched from your API.

Reference a variable as {{flow.key}} in templates, and in flow conditions.

Before you start

• You need the create and manage permission for flows.
• For an API variable, you need the endpoint URL and, if it needs a key, a secret to store.

Add a variable

1. In the flow editor, select the Variables tab.
2. Select Add variable. You can add up to 50.
3. Fill in the fields.

Field	What it does
Key	The variable's name, for example niftyOpen.
Data type	The type of the value.
Source	Constant, User attribute, Entry event property, Computed expression or API call.
Default / fallback value	Used when the value cannot be resolved.
Attribute / Event property / Expression	Shown for the matching source: the attribute or event property to read (blank uses the variable key), or the expression, for example {{message.amount}} on {{customer.city}}.

Remove a variable with Remove.

Use a variable in a message as {{flow.niftyOpen}}. Publishing fails with FLOW_VARIABLE_UNDEFINED if a message template uses {{flow.x}} and the flow defines no variable x (add | default:"-" to the placeholder to allow it).

Resolve a value from your API

Choose API call as the Source to fetch the value from an HTTP endpoint.

Field	What it does
Resolution scope	Per user (once per instance) looks the value up for each person. Per run (once per run, frozen) looks it up once so every recipient sees the same value.
On failure	Use fallback value, Skip this user, or Abort the run (per_run only). Abort stops the run before any message goes out.
Method	GET or POST.
URL	The endpoint. {{user.*}} works only at per-user scope. {{secrets.*}} works anywhere.
Headers	Request headers. Select Add header.
Response mapping	Maps a Variable key to a JSONPath in the response, for example $.data.NIFTY50.open. Select Add mapping.
Timeout (ms)	500 to 30,000.
Retries	0 to 5.
Cache TTL (seconds)	Per-user scope only. Reuse a result for up to a day.

Per-run variables need a Fixed time or Business event entry. Publishing is refused otherwise.

The flow looks the variable up for you, when a person enters (per user) or when the run starts (per run). You do not add a step for it. Use it in a message as {{message.flow.<key>}}. To call an endpoint part-way through a journey instead, use the Call API step. See Steps reference.

Store a secret

Secrets keep keys out of the request text.

1. Under Secrets, select Add or replace secret.
2. Enter a key such as marketApiKey and its value.
3. Use it in a header or URL as {{secrets.marketApiKey}}.

Stored secrets show with a lock icon. Their values are write-only: they are never shown again. Add the same key to replace one.

What happens next

Variables show up as tokens in the editor and in message personalisation. A run records the values it resolved. See Monitor a flow.