Variables, secrets & interpolation

${...} placeholders work in URLs, headers, params, bodies (string leaves), request names, WebSocket frames, gRPC messages and GraphQL variables.

FormResolves to
${env.NAME}process environment variable
${vars.name}the variables: block
${secrets.name}the secrets: block (redacted from logs/reports)
${data.source.column}current data row
${name}extracted variable / JS-set session.vars.name
${vu} / ${iteration} / ${scenario}the running VU id / iteration index / scenario name
${js: expr}evaluate JS in the VU's runtime, e.g. ${js: Date.now()}

Escape a literal with $${ → ${.

variables:
  tenant: acme
  api_base: "https://${env.REGION}.api.example.com"   # env resolved at startup

secrets:
  api_key: { env: API_KEY }          # from the environment
  db_pass: { file: ./secrets/db }    # from a file (trimmed)

scenarios:
  s:
    executor: constant-vus
    vus: 1
    duration: 1m
    flow:
      - request:
          url: /tenants/${vars.tenant}/ping
          headers:
            X-Api-Key: ${secrets.api_key}
            X-Request-Id: "${js: crypto.uuidv4()}"

Notes:

  • variables values may interpolate ${env.*} — resolved once at startup. Other namespaces resolve per use, inside the iteration.
  • Secrets never appear in console output, summaries or validation messages.
  • loadr validate errors on ${vars.*} / ${secrets.*} / ${data.*} references that don't exist (with did-you-mean), and warns on bare names no extractor produces.