What does Cache-Control: max-age mean?

max-age=N tells the browser (and any intermediate CDN) to treat the response as fresh for N seconds from the time it was received. After that, the client must revalidate with the server.

What is the difference between max-age and s-maxage?

s-maxage overrides max-age for shared caches (CDNs, proxies) only. Browsers ignore s-maxage and use max-age instead. Use s-maxage when you want a different TTL at the edge vs. in the browser.

When should I use no-cache vs no-store?

no-cache means the client must revalidate with the server before using a cached copy — the response can still be stored. no-store means the response must not be stored at all, anywhere. Use no-store only for sensitive data.

What is stale-while-revalidate?

stale-while-revalidate=N allows a client to serve a stale cached response for up to N seconds while it fetches a fresh one in the background. It trades occasional staleness for lower perceived latency.

How many seconds are in a year?

A standard year is 365 days = 31,536,000 seconds. This is the conventional value used for immutable long-lived assets (fonts, versioned JS/CSS).

Cache TTL Helper

Name: Cache TTL Helper
Availability: InStock
Author: Nham Vu

Convert cache TTL values between units and generate the correct Cache-Control header string.

TTL Input

Quick Presets

All Units

Cache-Control Header

Cache-Control: max-age=86400

Common Cache-Control Directives

Directive	Description
max-age=N	Response is fresh for N seconds. Applies to browsers and CDNs.
s-maxage=N	Overrides max-age for shared caches (CDNs, proxies). Browsers use max-age.
no-cache	Cache may store the response but must revalidate with the server before each use.
no-store	Response must not be stored anywhere. Use for sensitive or real-time data.
stale-while-revalidate=N	Serve stale content for up to N seconds while fetching a fresh response in the background.
immutable	Tells the browser the response will never change. Skip revalidation on reload. Use with versioned URLs.
public	Any cache (browser, CDN, proxy) may store the response, even if normally private.
private	Only the end-user browser may cache the response. CDNs and proxies must not store it.

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Summary

Convert cache TTL values between units and generate the correct Cache-Control header string.

How it works

Enter a TTL number and pick a unit (seconds, minutes, hours, days, or weeks).
The tool converts the value to all other time units.
Copy the ready-to-use Cache-Control: max-age=<seconds> header value.
Read the human-readable expiry breakdown (days, hours, minutes, seconds).
Use the preset buttons to jump to common durations like 1 hour or 7 days.

Use cases

Set an appropriate CDN or browser cache TTL for static assets.
Quickly convert a TTL specification from days to seconds for a config file.
Verify that a Cache-Control header matches the intended expiry duration.
Reference common Cache-Control directives while writing server config.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu