Response templates

Response templates turn an endpoint's response body into a safe Handlebars template. Reuse values from the incoming request, generate realistic data, and add simple conditional behavior without running arbitrary JavaScript.

Updated October 17, 2026

Quick start

Open an endpoint and enable Response template.
Add helpers to the response body.
Use the sample request panel to render a server-side preview.
Save the endpoint and set it Live.

{
  "id": "{{pathParam 'id'}}",
  "name": "{{body 'name' 'Anonymous'}}",
  "email": "{{faker 'internet.email'}}",
  "requestId": "{{header 'x-request-id' 'not-supplied'}}"
}

Templates are opt-in. When the switch is off, APIMock returns the response body exactly as written—even if it contains {{ braces }}.

Request helpers

Each helper takes a literal dot path and an optional fallback. Array values can be addressed by index, such as {{body 'items.0.name'}}. Missing values become an empty string when no fallback is supplied.

Helper	Example	Reads
body	{{body 'user.name' 'Anonymous'}}	JSON or form body value
queryParam	{{queryParam 'page' '1'}}	Query-string value
pathParam	{{pathParam 'id'}}	Named :path parameter
header	{{header 'x-request-id'}}	Case-insensitive request header
cookie	{{cookie 'session'}}	Cookie value

Request bodies are parsed for JSON media types and application/x-www-form-urlencoded. Repeated query and form fields are arrays and can be read with field.0.

Generate fake data

Use {{faker 'namespace.generator'}}. APIMock exposes a stable English-language allowlist; generator arguments and dynamic method names are intentionally unsupported.

IDs and values

string.uuid, datatype.boolean, number.int

People

person.firstName, person.lastName, person.fullName, person.jobTitle

Internet

internet.email, internet.username, internet.url, internet.ipv4

Contact and location

phone.number, location.streetAddress, location.city, location.state, location.country, location.zipCode

Business

company.name, commerce.productName, commerce.price, finance.currencyCode

Text

lorem.word, lorem.sentence, lorem.paragraph

Dates

date.past, date.future, date.recent

{
  "id": "{{faker 'string.uuid'}}",
  "name": "{{faker 'person.fullName'}}",
  "product": "{{faker 'commerce.productName'}}",
  "createdAt": "{{faker 'date.recent'}}"
}

Logic and arrays

Use if, unless, and a single bounded each loop. Comparison helpers are eq, ne, and, or, and not.

{
  "active": {{#if (eq (queryParam 'status') 'active')}}true{{else}}false{{/if}},
  "items": [
    {{#each (body 'items')}}
      {"name": "{{this.name}}"}{{#unless @last}},{{/unless}}
    {{/each}}
  ]
}

Escaping and JSON

Double braces use standard Handlebars HTML escaping. Triple braces emit raw text. Use the json helper when inserting an object, array, or string as a JSON value.

{
  "profile": {{{json (body 'profile')}}}
}

Templates can deliberately echo headers or cookies into a response. Avoid returning credentials or personal data. Request-log redaction does not change the response you configured.

Limits and errors

Template source: 64 KiB
Request body available to a template: 1 MiB
Rendered response body: 2 MiB
Each loop: 100 items, with nested loops disabled

The editor blocks syntax, unknown-helper, and limit errors. A body over the request limit returns 413. Unexpected render failures return 500 with an X-APIMock-Request-Id header for Inspector correlation.

Not available in this release: Faker arguments or locales, XML/SOAP parsing, stateful helpers, arithmetic/date/string operators, nested loops, and templating of headers, status, delay, or content type.

Build your first response template

Create an endpoint, enable templating, and verify it with the server preview.

Create endpoint