Variables

Inline variable definition

Variables are defined directly in the .http file using the @ prefix:

@hostname = api.example.com
@port = 8080
@baseUrl = https://{{hostname}}:{{port}}

Universal Supported identically by all major implementations.

The @name = value syntax is supported by all major implementations. Variables can reference other variables in their definitions.

Variable names must not contain spaces. VS Code REST Client requires a complete line per definition with whitespace trimmed.

Lazy variables

httpyac

httpyac introduces a distinction between fixed variables (evaluated at parse time, using =) and lazy variables (evaluated at execution time, using :=):

@eager = {{$timestamp}}
@lazy := {{$timestamp}}

The eager variable captures the timestamp once when the file is parsed. The lazy variable generates a fresh timestamp each time it's used.

Variable substitution

All implementations use double curly braces for variable substitution:

GET https://{{hostname}}/api/{{version}}/users
Authorization: Bearer {{token}}

Universal Supported identically by all major implementations.

The {{variableName}} syntax is universal.

Percent-encoding substitution

VS Code

VS Code REST Client supports {{%variableName}} which URL-encodes the variable value before substitution.

Variable scoping and precedence

Variable resolution order differs between implementations:

VS Code REST Client (highest to lowest):

1. Request variables (named request responses)
2. File variables (@var = value)
3. Prompt variables (@prompt)
4. Environment variables (from settings.json)

JetBrains (highest to lowest):

1. Per-request variables (set in pre-request scripts)
2. In-place file variables (@var = value)
3. Global variables (client.global.set())
4. Environment variables (from http-client.env.json)

httpyac (highest to lowest):

1. Request-scoped variables
2. File-global variables
3. Environment variables (from .env, http-client.env.json, or config files)

Named request variables (response chaining)

Responses from named requests can be referenced as variables. The syntax differs significantly between implementations.

VS Code REST Client

# @name login
POST https://api.example.com/auth
Content-Type: application/json

{"username": "admin", "password": "secret"}

###
GET https://api.example.com/protected
Authorization: Bearer {{login.response.body.$.token}}

JetBrains

POST https://api.example.com/auth
Content-Type: application/json

{"username": "admin", "password": "secret"}

> {%
client.global.set("auth_token", response.body.token);
%}

###
GET https://api.example.com/protected
Authorization: Bearer {{auth_token}}

httpyac

# @name login
POST https://api.example.com/auth

###
# @ref login
GET https://api.example.com/protected
Authorization: Bearer {{login.token}}

VS Code REST Client uses dot-path notation with these reference patterns:

• {{name.response.body.$.jsonPath}} — JSONPath into JSON response
• {{name.response.body.//xpathExpr}} — XPath into XML response
• {{name.response.body.*}} — entire response body
• {{name.response.headers.Header-Name}} — response header value
• {{name.request.body.*}} — original request body

JetBrains uses response handler scripts to store values in global variables, then references them as {{variableName}}. There is no direct dot-path syntax.

httpyac supports the # @name / # @ref pattern, where a named request's parsed response body becomes available as a variable.

Visual Studio 2022 (since v17.12) supports VS Code REST Client-style request variables.

Feature	VS Code	JetBrains	httpyac	VS 2022	kulala
Inline variable definition (@var = value)	✓	✓	✓	✓	✓
Variable substitution ({{variableName}})	✓	✓	✓	✓	✓
Percent-encoding substitution ({{%var}}) URL-encodes the variable value. Unique to VS Code REST Client.	✓	✗	✗	✗	✗
Lazy variables (@var := value) Evaluated at execution time rather than parse time.	✗	✗	✓	✗	✗
Named request response chaining Syntax differs: VS Code uses dot-path ({{name.response.body.$.path}}), JetBrains uses script-based global variables, httpyac uses @ref.	✓	✓	✓	✓	✓
Environments in settings.json	✓	✗	✗	✗	✗
http-client.env.json	✗	✓	✓	✓	✓
http-client.private.env.json	✗	✓	✓	✗	✓
http-client.env.json.user Microsoft-specific override file.	✗	✗	✗	✓	✗
.env dotenv files VS Code REST Client and VS 2022 support via {{$dotenv NAME}} accessor. httpyac and kulala parse .env files natively.	◐	✗	✓	◐	✓
JS/JSON config file httpyac.config.js or .httpyac.js	✗	✗	✓	✗	✗
$shared environment	✓	✗	✓	✓	✗
Secrets providers (Azure Key Vault, etc.) ASP.NET Core User Secrets, Azure Key Vault, DPAPI.	✗	✗	✗	✓	✗