Spillway - API Load Testing

Spillway is a native macOS load and performance testing tool for HTTP APIs and web services. Think JMeter, k6, or Gatling — but as a first-class Mac document app. No scripts, no YAML, no terminal required. Design a test plan visually, press Run, and watch the results stream in live.

BUILT FOR THE MAC Every test plan is a document you open, edit, save, and share. Full undo/redo, a familiar layout, and native SwiftUI throughout — it feels like a Mac app because it is one.

MODEL REAL-WORLD LOAD • User-based model — simulate a fixed pool of virtual users • Throughput-based model — drive a target request rate (requests per second) • Ramp load up or down over time to find your breaking point • Constant, spike, and long-running soak profiles

BUILD REALISTIC SCENARIOS • Sequence HTTP requests with full control over method, headers, query parameters, and body • Loops, conditions, and think-time pauses • Extract values from responses with regex or JSON queries, then feed them into later requests • Data-driven testing from CSV input • Import your existing JMeter (.jmx) test plans • Dynamic variables with a token expression language and built-in functions • OAuth 2.0 authentication and automatic cookie/session handling

SEE WHAT'S HAPPENING, LIVE • Response-time percentiles (p50 / p90 / p95 / p99) • Throughput and error-rate charts that update as the test runs • Per-request timing and full request/response inspection • CPU and memory telemetry for your load generators • Compare executions to see the differences in performance profile