# Cache-Control

Category: [Technical SEO](https://seo-geo-glossary.com/en/glossary/category/technical-seo/) › [Servers, HTTP & caching](https://seo-geo-glossary.com/en/glossary/category/technical-seo/servers-http-caching/) · Also known as: Cache-Control header

**Cache-Control** is an HTTP header that tells browsers and shared caches such as CDNs whether and for how long they may store a response. It can appear in responses and in requests. Directives are separated by commas and are case-insensitive.

## Which directives are important?

| Directive | Meaning |
|---|---|
| `max-age=N` | The response stays fresh for N seconds after it was generated. |
| `s-maxage=N` | Same as `max-age`, but only for shared caches such as CDNs. |
| `no-cache` | The response may be stored, but must be revalidated with the server before each reuse. |
| `no-store` | The response must not be stored in any cache. |
| `private` | Only a private cache, such as the browser, may store it. |
| `public` | Shared caches may store it, even for requests with authorization. |
| `must-revalidate` | After it becomes stale, the response must be revalidated before reuse. |
| `immutable` | The response will not change while fresh, so no revalidation is needed. |
| `stale-while-revalidate=N` | A stale response may be served for N seconds while a fresh copy is fetched in the background. |

## What is the difference between no-cache and no-store?

The names are easy to mix up. `no-cache` allows storing and requires a check with the server before reuse, which often results in a `304 Not Modified`. `no-store` forbids storing. According to RFC 9111, `no-store` is not a reliable mechanism for privacy, since it relies on caches behaving as specified.

## Common patterns

- Versioned static files: `Cache-Control: max-age=31536000, immutable`
- HTML pages that should always be checked: `Cache-Control: no-cache`
- Personalized content: `Cache-Control: private`
- Content for a CDN: `Cache-Control: public, s-maxage=3600`

## Example

```http
HTTP/1.1 200 OK
Cache-Control: public, max-age=604800
ETag: "33a64df5"
```

## Cache-Control and crawlers

Google's crawlers support ETag and Last-Modified for conditional requests. Setting a validator together with `Cache-Control` lets repeated requests end in `304 Not Modified`. Google writes that `max-age` is not required, but worth considering as an addition so crawlers can tell when to recrawl a URL. Other HTTP caching directives are not supported by Google.

## Cache headers and 304 compared

| Header / status | Request counterpart | What it does | Relevance for Google's crawlers |
|---|---|---|---|
| Cache-Control | – (directives can also appear in requests) | lists directives for caches, e.g. max-age (fresh for N seconds), no-cache (reuse only after revalidation), no-store (do not store) | max-age is optional and helps crawlers decide when to recrawl the URL; Google does not support other caching directives |
| ETag | If-None-Match | identifier for the current version of a resource | supported and recommended by Google because it has no date formatting issues; takes precedence when both validators are present |
| Last-Modified | If-Modified-Since | date and time at which the server believes the resource was last modified | supported; the date must follow the HTTP format, e.g. Fri, 4 Sep 1998 19:15:56 GMT |
| 304 Not Modified | response to a conditional GET or HEAD request | signals that the stored copy is still valid; the response has no body | the crawler tells the next system that the content is the same as at the last crawl; Search may recalculate signals, otherwise no effect on indexing |

Sources: [Google Crawling Infrastructure: Overview of Google crawlers and fetchers, HTTP caching (last updated 2026-06-12)](https://developers.google.com/crawling/docs/crawlers-fetchers/overview-google-crawlers); [Google Search Central Blog: Crawling December: HTTP caching (2024-12-09)](https://developers.google.com/search/blog/2024/12/crawling-december-caching); [Google Crawling Infrastructure: HTTP status codes, network and DNS errors (last updated 2026-02-04)](https://developers.google.com/crawling/docs/troubleshooting/http-status-codes); [MDN: HTTP caching](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching); [RFC 9111: HTTP Caching](https://www.rfc-editor.org/rfc/rfc9111.html); [RFC 9110: HTTP Semantics (8.8.2 Last-Modified, 8.8.3 ETag, 15.4.5 304)](https://www.rfc-editor.org/rfc/rfc9110.html). Last checked: October 8, 2026

## Related terms

- [Browser caching](https://seo-geo-glossary.com/en/glossary/browser-caching/index.md)
- [Google cache](https://seo-geo-glossary.com/en/glossary/google-cache/index.md)
- [HTTP header](https://seo-geo-glossary.com/en/glossary/http-header/index.md)
- [ETag](https://seo-geo-glossary.com/en/glossary/etag/index.md)
- [Last-Modified header](https://seo-geo-glossary.com/en/glossary/last-modified-header/index.md)
- [CDN (content delivery network)](https://seo-geo-glossary.com/en/glossary/cdn/index.md)

## Sources

- [Cache-Control – MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control)
- [HTTP Caching, RFC 9111](https://www.rfc-editor.org/rfc/rfc9111)
- [HTTP caching – MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/Caching)
- [Overview of Google crawlers and fetchers (HTTP caching) – Google Search Central](https://developers.google.com/crawling/docs/crawlers-fetchers/overview-google-crawlers)

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Last updated: October 8, 2026
URL: https://seo-geo-glossary.com/en/glossary/cache-control/