Instruments
Working models and measurement tools, free to operate. Each one runs in your browser, ships with the reasoning behind it, and keeps nothing — no signup, no stored data. Most exist because an analysis needed a way to show a mechanism rather than describe it.
Catalog
9 instrumentsAd auction simulator
A live generalized second-price auction: drag bids and quality, watch rank and price recompute.
SimulationFont loading timeline
Watch font-display choose between block, swap and failure periods — and the layout shift that follows.
SimulationCache lifecycle simulator
Write a Cache-Control field, advance the clock, fire requests — and watch freshness and revalidation resolve.
SimulationIdempotency lab
Retry a timed-out write and watch it double-charge — then add an idempotency key and watch it not.
SimulationAgent loop debugger
Step through a real tool-calling episode, watch the context fill, and drag reliability to see p^n collapse.
SimulationWebsite speed test
Measure a page and rank it against the observatory corpus of real sector homepages.
MeasurementContrast ratio checker
WCAG contrast ratio between any two colours, with AA and AAA verdicts for normal and large text.
ReferenceAccessible name inspector
Compose an element and watch the accessible name computation resolve, step by step.
ReferenceROI calculator
Total return, annualized return and net gain, with the formulas shown.
Arithmetic