Developer Tools

Cache-Control Header Builder

Build and parse Cache-Control HTTP headers in your browser. Pick directives, get max-age presets, server snippets, and a plain-English explanation.

Quick presets

Tap a preset to load common Cache-Control patterns.

Visibility

Flag directives

Numeric directives (seconds)

max-age1 hour

Browser freshness lifetime.

s-maxage

Shared cache (CDN) freshness lifetime; overrides max-age for shared caches.

stale-while-revalidate

Window where caches may serve stale while revalidating in background.

stale-if-error

Window where caches may serve stale if origin errors or times out.

Generated header

Cache-Control: public, max-age=3600

Any cache may store this response. Browser may serve cached for 1 hour.

Server snippets

Drop into your server config or framework. Customize the path or matcher to fit your routing.

Raw header

Cache-Control: public, max-age=3600

Apache (.htaccess / VirtualHost)

<IfModule mod_headers.c>
  Header set Cache-Control "public, max-age=3600"
</IfModule>

Nginx

add_header Cache-Control "public, max-age=3600" always;

Vercel (vercel.json)

{
  "headers": [
    {
      "source": "/(.*)",
      "headers": [
        {
          "key": "Cache-Control",
          "value": "public, max-age=3600"
        }
      ]
    }
  ]
}

Netlify (_headers)

/*
  Cache-Control: public, max-age=3600

Cloudflare Worker

const response = await fetch(request);
const headers = new Headers(response.headers);
headers.set("Cache-Control", "public, max-age=3600");
return new Response(response.body, { status: response.status, headers });

Next.js (next.config.js headers)

async headers() {
  return [
    {
      source: "/:path*",
      headers: [
        { key: "Cache-Control", value: "public, max-age=3600" },
      ],
    },
  ];
}

Express.js

app.use((req, res, next) => {
  res.setHeader("Cache-Control", "public, max-age=3600");
  next();
});

Common durations

Click a preset to load it as max-age. Useful when you forget the exact second count.

Quick reference

public vs private

public lets shared caches store the response. private restricts caching to the user's browser.

no-cache vs no-store

no-cache caches but revalidates each time. no-store forbids caching entirely.

max-age vs s-maxage

max-age applies to all caches. s-maxage applies only to shared caches and overrides max-age for them.

immutable

Promises the body never changes for this URL. Browsers skip revalidation while fresh. Pair with a long max-age.

stale-while-revalidate

After expiry, caches may serve stale while revalidating in the background. Improves perceived latency.

must-revalidate

Once stale, caches must revalidate before reuse. Stale responses cannot be served on origin failure.

How to use

Choose the Build header tab to compose a Cache-Control value, or the Parse and explain tab to paste an existing value.
Builder: pick a quick preset (Static asset, HTML page, API response private, CDN public, Never cache, or Stale-while-revalidate) or set visibility, flag directives, and numeric directives manually. Each numeric field shows its value in human time.
Read the live header preview, the plain-English explanation, and any conflict warnings. Common-duration presets quickly fill max-age with 1 minute, 1 hour, 1 day, 1 week, 30 days, or 1 year.
Copy the raw header, or pick a server snippet for Apache, Nginx, Vercel, Netlify, Cloudflare Workers, Next.js, or Express to drop straight into your config.
Parser: paste a Cache-Control value (with or without the Cache-Control: prefix). The tool splits directives, explains each one, flags conflicts and duplicates, and summarizes effective browser, shared cache, and revalidation behavior.

About this tool

Cache-Control Header Builder is a two-mode browser tool for the HTTP Cache-Control header defined in RFC 7234 and RFC 9111. The Build tab lets you compose a header by toggling directives instead of memorizing the syntax: pick visibility (public, private, or unset), flip flag directives (no-cache, no-store, no-transform, must-revalidate, proxy-revalidate, immutable, must-understand), and enter numeric directives (max-age, s-maxage, stale-while-revalidate, stale-if-error). Each numeric input shows its value in human time as you type, and a row of common-duration presets covers 1 minute, 5 minutes, 1 hour, 1 day, 1 week, 30 days, and 1 year so you do not have to remember that one year is 31,536,000 seconds. Six quick presets cover the patterns real apps reach for: hashed static assets (1 year, immutable), HTML pages (no-cache for stale revalidation), private API responses, public CDN-cacheable for 5 minutes with a 24-hour stale-while-revalidate window, never-cache for sensitive responses, and stale-while-revalidate for blog and catalog pages. The header preview updates live, a plain-English explanation summarizes browser, shared-cache, and revalidation behavior, and a conflict checker flags mistakes that other generators miss: no-store with max-age, immutable without a long max-age, proxy-revalidate on a private response, and s-maxage on a private response. Server-snippet output is ready to paste into Apache (mod_headers), Nginx (add_header), Vercel (vercel.json), Netlify (_headers), Cloudflare Workers, the Next.js headers config, and Express middleware, with the directive escaped correctly so quotes do not break your config. The Parse tab takes any Cache-Control value, splits it into directives (handling quoted values, the optional Cache-Control: prefix, and an arbitrary number of spaces), explains each directive with the spec semantics, flags non-numeric values where the spec requires delta-seconds, surfaces duplicate directives that lead to undefined behavior across caches, and summarizes the effective browser cache lifetime, shared cache lifetime, and revalidation policy in three quick cards. A reference grid contrasts the directive pairs that confuse most developers (public vs private, no-cache vs no-store, max-age vs s-maxage, immutable, stale-while-revalidate, must-revalidate) so the page doubles as a study sheet. Useful for setting up CDN caching policies, writing the headers for a Next.js or Astro deployment, debugging why a CDN keeps serving a stale response, reviewing a security-sensitive endpoint, or preparing the cache headers for a static asset pipeline. Everything runs locally in your browser. Headers, directive values, and snippets are never uploaded.

Free to use. Works in your browser. No signup, no login.

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