Description
Calculate remaining cache freshness lifetime and mark exact lifetime equality as no longer fresh.
Web protocol data has several layers: a complete message or URL, individual fields or components, and the literal tokens within them. Delimiter presence, spelling, comparison rules, and parser normalization can affect results. A check of one component needs its stated scope before it can be used in a larger parser or policy decision.
Calculate remaining cache freshness lifetime and mark exact lifetime equality as no longer fresh.
When to use this tool
Use HTTP Age Cache Freshness Residual when you need one stated URL, header, or protocol-component check in a diagnostic or parser workflow. Supply the input level specified below.
How to use the tool and how it works
- Enter freshnessLifetime, currentAge. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read remaining, fresh. Inspect fresh before interpreting the associated values.
Require nonnegative freshnessLifetime and currentAge. Return remaining=freshnessLifetime-currentAge and fresh only when remaining is strictly positive.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| freshnessLifetime | Freshness Lifetime | Required. Finite number; minimum 0. |
| currentAge | Current Age | Required. Finite number; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| remaining | Remaining | Required. Finite number. |
| fresh | Fresh | Required. Boolean. |
{
"input": {
"freshnessLifetime": 60,
"currentAge": 45
},
"output": {
"remaining": 15,
"fresh": true
}
}Limitations and assumptions
- At exact lifetime equality fresh is false. Both times need a common unit; the supplied lifetime is not inferred from headers, and directives, validation, and stale-response allowances are outside this term.
- The field tables state structural bounds; the mechanics also specify cross-field constraints. Malformed inputs and unsupported domains cause errors. A successful false flag, empty branch value, or zero placeholder has the meaning stated above and is distinct from an input error.
Alternative or Complementary methods
Use a complete URL or header parser when the task involves an entire field or message. Test actual browser, server, or cache behavior separately when a security or protocol decision depends on more than this component.
References
Similar or alternative tools
- Web: HTTP Age Date Response Adjustment
Apply RFC9111 apparent-age/response-delay adjustment and resident time from explicit parsed timestamps and Age; not a cache freshness or header parser.
- HTTP Cache Control Maxstale Unbounded Token
Match token as case-insensitive max-stale, optionally followed by equals and unsigned digits.