loadr

loadr is a load testing platform in a single binary. It combines the two dominant traditions in load testing:

• k6's model: scriptable tests, open/closed load models with precise executors, a first-class metrics engine with thresholds as pass/fail criteria, and a great CLI experience.
• JMeter's breadth: rich assertions (response code, body, JSONPath, XPath, size, duration), extractors (regex, boundary, CSS, XPath), timers (constant, uniform, gaussian, constant-throughput), CSV data sets, cookie management, and broad protocol coverage.

…and adds what both lack: declarative YAML test definitions validated by a JSON Schema, a plugin system (sandboxed WASM components and native libraries), built-in distributed execution with mathematically correct percentile aggregation, and a built-in management web UI.

A taste

name: smoke
defaults:
  http: { base_url: https://api.example.com }

scenarios:
  api:
    executor: constant-arrival-rate
    rate: 100
    duration: 5m
    pre_allocated_vus: 50
    flow:
      - request:
          url: /search?q=widgets
          extract: [ { type: jsonpath, name: first, expression: "$.results[0].id" } ]
          checks: [ { type: status, equals: 200 } ]
      - request: { url: "/items/${first}" }

thresholds:
  http_req_duration: [ "p(95)<300" ]
  http_req_failed: [ "rate<0.01" ]

loadr run smoke.yaml          # exit code 0 when thresholds pass, 99 when not

How the pieces fit

Continue with Installation, or jump to the YAML reference, the JS API, or the migration guides.