Liquid is a templating language supported by OneSignal to personalize messages across channels including email, push, SMS, in-app, and Live Activities. It uses tags, filters, and conditionals to dynamically customize message content. To learn more about Liquid syntax, see the official Liquid documentation.

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Supported fields by message type

  • Subject, Reply-to, and Pre-header
  • Message Body
  • Image substitution in HTML blocks. Example: <img src="{{image_url}}"/>
  • Button block actions like URLs, Mail to, and other fields.

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Basic syntax

Liquid uses two main syntax structures:
  1. Output Tags: {{ ... }} - Display data from a variable or object.
  2. Logic Tags: {% ... %} - Execute conditional statements or loops.

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Data sources

SourceExampleDescription
Tag{{ first_name }}OneSignal SDK or API (tags)
Property{{ subscription.email }}System-managed (email, external_id, language, etc.)
Journey Name{{ journey.name }}System-managed
Custom Data{{ message.custom_data.key }}custom_data passed in Create Message API
Data Feeds{{ data_feed.cart.size }}Data Feeds let you pull real-time data from your APIs directly into messages at send time.
Custom Events - BETA{{ journey.last_event.name }}Set via Event Triggered Journeys, Wait Until nodes

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Conditionals

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Operators

  • ==, !=, >, <, >=, <=
  • and, or
  • contains (string or array)
Operations run right to left. Parentheses are not supported.
liquid
{% if true or false and false %}
  This is true.
{% endif %}

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if, elsif, else

liquid
{%- assign userLang = subscription.language -%}
{% if userLang == "es" -%}
Hola {{ first_name }}!
{%- elsif userLang == "fr" -%}
Bonjour {{ first_name }}!
{%- else -%}
Hello {{ first_name }}!
{%- endif %}

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unless

liquid
{% unless level == "1" %}
  Great job getting past the first level!
{% endunless %}

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Filters

Apply filters using {{ variable | filter }} to adjust how the data is displayed.

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default

Assign a default value if the property is empty or does not exist.
liquid
Hello {{ first_name | default: "there" }}.

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date

The date filter converts a timestamp into another date format. The format for this syntax is the same as strftime. The input uses the same format as Ruby’s Time.parse. Set dates as a unix timestamp in seconds with tags. This allows for use of both liquid syntax personalization and segmentation with Time Operators. For example, a tag might look like: bill_due : 1687968776
liquid
{{ bill_due | date: "%a, %b %d, %y" }}
{{ "now" | date: "%Y-%m-%d %H:%M" }}
Result
Wed, Jun 28, 23
liquid
{{ bill_due | date: "%Y" }}
Result
2023
Date formatting works on strings if they contain well-formatted dates.
liquid
{{ "March 14, 2016" | date: "%b %d, %y" }}
Result
Mar 14, 16
To get the current time, pass the special word now (or today) along with the date filter.
liquid
This message was sent at {{ "now" | date: "%Y-%m-%d %H:%M" }}.
Result
This message was sent at 2022-11-02 14:39.
The current time will be rendered in the message based on when the message is sent to the recipient. If you are testing the message, you will see the current time as when the test message was sent.

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capitalize

This filter makes the first character of a string capitalized and converts the remaining characters to lowercase.
liquid
{{ "my GREAT title" | capitalize }}
Result
My great title

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round

This filter rounds a number to the nearest integer, or, if a number is passed as an argument, to that number of decimal places.
liquid
{{ 1.2 | round }}
  {{ 2.7 | round }}
{{ 183.357 | round: 2 }}
Result
1
3
183.36

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pluralize

This filter returns the singular or plural form of a string based on a given number. The number must be a whole number and can be provided as a string. Both the singular and plural forms of a string must be provided.
liquid
{{ 1 | pluralize: "singular", "plural" }}
{{ 2 | pluralize: "singular", "plural" }}
1 {{ 1 | pluralize: "person", "people" }}
2 {{ 2 | pluralize: "person", "people" }}
2 {{ "2" | pluralize: "person", "people" }}
Result
singular
plural
1 person
2 people
2 people

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Iteration

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for loops

Repeatedly executes a block of code. For a full list of attributes available within a for loop, refer to the for loop object.
liquid
{% for product in message.custom_data.products %}
  - {{ product.name }}
  {% else %}
    Sorry, we're sold out of all products.
  {% endfor %}
Request Body
{
  "app_id": "5eb5a37e-b458-11e3-ac11-000c2940e62c",
    "template_id": "be4a8044-bbd6-11e4-a581-000c2940e62c",
    "custom_data": {
      "products": [
        { "name": "Sweater" },
        { "name": "Hat" },
        { "name": "Shirt" }
      ]
    }
  }
Results
  - Sweater
  - Hat
  - Shirt

  // if message.custom_data.products is empty
  Sorry we're sold out of all products
While powerful and flexible, the usage of for loops in liquid syntax can lead to poor notification delivery performance in certain rare cases. Be mindful of your usage of for loops. Also note that we prevent the usage of for loops in a few Push Channel fields: contents, headings, subtitle, apns_alert, and url

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limit & offset

Limits the loop to the specified number of iterations. For example, if you only want to show 4 products in a message, you could use Limits and Offsets to specify the number of products shown.
Data
great_numbers = [1,2,3,4,5,5]
liquid
{% for number in great_numbers limit:2 %}
  {{ number }}
{% endfor %}
Result
1 2
To begin the loop at the specified index, add an offset value:
Data
great_numbers = [1,2,3,4,5,5]
liquid
{% for number in great_numbers limit: 3 %}
  {{ number }}
{% endfor %}

{% for number in great_numbers limit: 3 offset: 3 %}
  {{ number }}
{% endfor %}
```text Result
1 2 3
4 5 6

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where

Creates an array including only the objects with a given property value, or any truthy value by default. In this example, assume you have a list of products and you want to show your kitchen products separately. Using where, you can create an array containing only the products that have a type of kitchen.
Data
products = [
  {name:"Vacuum", type:"electronics"},
  {name:"Spatula", type:"kitchen"},
  {name:"Television", type:"electronics"},
  {name:"Garlic press", type:"kitchen"}
]
liquid
All products:
{% for product in products %}
- {{ product.name }}
{% endfor %}

{% assign kitchen_products = products | where: "type", "kitchen" %}

Kitchen products:
{% for product in kitchen_products %}
- {{ product.name }}
{% endfor %}
Result
All products:
  - Vacuum
  - Spatula
  - Television
  - Garlic press

Kitchen products:
- Spatula
- Garlic press

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String Manipulation

Occasionally you may have data tags that contain strings that is in a format that is not suitable to be shown directly to your users, and you may need to manipulate the string to adjust the format. Below is a table of liquid syntax commands that can be used to adjust strings. You can use string manipulation both on Tags and directly on strings written into the message.
CommandDescriptionExampleExample Output
replaceReplaces a substring with another string.{{ 'hello world' | replace: 'world', 'there' }}hello there
capitalizeCapitalizes the first letter of a string.{{ 'hello' | capitalize }}Hello
upcaseConverts a string to uppercase.{{ 'hello' | upcase }}HELLO
downcaseConverts a string to lowercase.{{ 'HELLO' | downcase }}hello
stripRemoves leading and trailing whitespace from a string.{{ ' hello ' | strip }}hello
strip_htmlRemoves all HTML tags from a string.{{ '<p>hello</p>' | strip_html }}hello
truncateShortens a string to a specified length, adding an ellipsis (…) if needed.{{ 'This is a long sentence' | truncate: 10 }}This is a…
truncatewordsTruncates a string after a certain number of words.{{ 'This is a long sentence' | truncatewords: 2 }}This is…
replace_firstReplaces the first occurrence of a substring.{{ 'hello world' | replace_first: 'world', 'there' }}hello there
prependAdds a string to the beginning of another string.{{ 'world' | prepend: 'hello ' }}hello world
appendAdds a string to the end of another string.{{ 'hello' | append: ' world' }}hello world
lstripRemoves leading whitespace from a string.{{ ' hello' | lstrip }}hello
rstripRemoves trailing whitespace from a string.{{ 'hello ' | rstrip }}hello

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FAQ

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Why is substitution not working?

  • In-App Messages do not support property substitution.
  • Tag substitution does not work when using “Send Test Message”.
  • Tag keys must be alphanumeric, or use _ and - (no periods or spaces).
  • Substitution does not appear in preview mode — send a real message to test.

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How to control whitespace and newlines?

Use hyphens: {{- ... -}}, {%- ... -%} to trim surrounding whitespace. See Whitespace control for more details.

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How to handle user-generated content?

Wrap user-generated text in {% raw %} and {% endraw %} to prevent Liquid parsing. See “raw” syntax.
json
{
  "contents": {
    "en": "{% raw %} Your user-generated content with invalid characters like {{ {% endraw %}"
  }
}