Why is now an explicit input?

It keeps the calculation deterministic: identical input produces identical output.

When is S-Maxage used?

It takes precedence over max-age when shared cache is selected.

It verifies standard calculations. Check vendor directives and configuration separately.

Choose cache type
Select a browser/private cache or shared CDN/proxy cache.
Enter timing and headers
Provide request, response, evaluation times, and response headers.
Compare age and lifetime
Inspect current age, freshness lifetime, and validation requirements.

This covers explicit RFC 9111 freshness. It does not reproduce vendor directives, heuristic freshness, cache keys, or Vary selection.

Why is now an explicit input?: It keeps the calculation deterministic: identical input produces identical output.
When is S-Maxage used?: It takes precedence over max-age when shared cache is selected.
Will this exactly match my CDN?: It verifies standard calculations. Check vendor directives and configuration separately.