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[Cache] Adds section about no-cache and no-store directives #21783

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Apr 17, 2025
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[Cache] Adds section about no-cache and no-store directives #21783

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137 changes: 13 additions & 124 deletions src/content/docs/cache/concepts/cache-control.mdx
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Expand Up @@ -101,130 +101,19 @@ The following section covers the directives and behavioral conditions associated

The table below lists directives and their behaviors when Origin Cache Control is disabled and when it is enabled.

<table>
<tbody>
<th colspan="5" rowspan="1">
Directive
</th>
<th colspan="5" rowspan="1">
Origin Cache Control disabled behavior
</th>
<th colspan="5" rowspan="1">
Origin Cache Control enabled behavior
</th>
<tr>
<td colspan="5" rowspan="1">
<code>s-maxage=0</code>
</td>
<td colspan="5" rowspan="1">
Will not cache.
</td>
<td colspan="5" rowspan="1">
Caches and always revalidates
</td>
</tr>
<tr>
<td colspan="5" rowspan="1">
<code>max-age=0</code>
</td>
<td colspan="5" rowspan="1">
Will not cache.
</td>
<td colspan="5" rowspan="1">
Caches and always revalidates.
</td>
</tr>
<tr>
<td colspan="5" rowspan="1">
<code>no-cache</code>
</td>
<td colspan="5" rowspan="1">
Will not cache.
</td>
<td colspan="5" rowspan="1">
Caches and always revalidates. Does not serve stale.
</td>
</tr>
<tr>
<td colspan="5" rowspan="1">
<code>no-cache=&lt;headers&gt;</code>
</td>
<td colspan="5" rowspan="1">
Will not cache.
</td>
<td colspan="5" rowspan="1">
Caches if headers mentioned in <code>no-cache=&lt;headers&gt;</code> do not exist. Always
revalidates if any header mentioned in <code>no-cache=&lt;headers&gt;</code> is present.
</td>
</tr>
<tr>
<td colspan="5" rowspan="1">
<code>Private=&lt;headers&gt;</code>
</td>
<td colspan="5" rowspan="1">
Will not cache.
</td>
<td colspan="5" rowspan="1">
Does not cache <code>&lt;headers&gt;</code> values mentioned in <code>Private=&lt;headers&gt;</code> directive.
</td>
</tr>
<tr>
<td colspan="5" rowspan="1">
<code>must-revalidate</code>
</td>
<td colspan="5" rowspan="1">
Cache directive is ignored and stale is served.
</td>
<td colspan="5" rowspan="1">
Does not serve stale. Must revalidate for CDN and for browser.
</td>
</tr>
<tr>
<td colspan="5" rowspan="1">
<code>proxy-revalidate</code>
</td>
<td colspan="5" rowspan="1">
Cache directive is ignored and stale is served.
</td>
<td colspan="5" rowspan="1">
Does not serve stale. Must revalidate for CDN but not for browser.
</td>
</tr>
<tr>
<td colspan="5" rowspan="1">
<code>no-transform</code>
</td>
<td colspan="5" rowspan="1">
May (un)Gzip, Polish, email filter, etc.
</td>
<td colspan="5" rowspan="1">
Does not transform body.
</td>
</tr>
<tr>
<td colspan="5" rowspan="1">
<code>s-maxage=delta, delta>1</code>
</td>
<td colspan="5" rowspan="1">
Same as <code>max-age</code>.
</td>
<td colspan="5" rowspan="1">
<code>Max-age</code> and <code>proxy-revalidate</code>.
</td>
</tr>
<tr>
<td colspan="5" rowspan="1">
<code>immutable</code>
</td>
<td colspan="5" rowspan="1">
Not proxied downstream.
</td>
<td colspan="5" rowspan="1">
Proxied downstream. Browser facing, does not impact caching proxies.
</td>
</tr>
</tbody>
</table>
| Directive | Origin Cache Control Disabled Behavior | Origin Cache Control Enabled Behavior |
|---------------------------|---------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------|
| `s-maxage=0` | Will not cache. | Caches and always revalidates |
| `max-age=0` | Will not cache. | Caches and always revalidates. |
| `no-cache` | Will not cache. | Caches and always revalidates. Does not serve stale. |
| `no-cache=<headers>` | Will not cache. | Caches if headers mentioned in `no-cache=<headers>` do not exist. Always revalidates if any header mentioned in `no-cache=<headers>` is present.|
| `Private=<headers>` | Will not cache. | Does not cache `<headers>` values mentioned in `Private=<headers>` directive. |
| `must-revalidate` | Cache directive is ignored and stale is served. | Does not serve stale. Must revalidate for CDN and for browser. |
| `proxy-revalidate` | Cache directive is ignored and stale is served. | Does not serve stale. Must revalidate for CDN but not for browser. |
| `no-transform` | May (un)Gzip, Polish, email filter, etc. | Does not transform body. |
| `s-maxage=delta, delta>1` | Same as `max-age`. | `Max-age` and `proxy-revalidate`. |
| `immutable` | Not proxied downstream. | Proxied downstream. Browser facing, does not impact caching proxies. |
| `no-store` | Will not cache. | Wil not cache. |

### Conditions

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19 changes: 19 additions & 0 deletions src/content/docs/cache/concepts/cdn-cache-control.mdx
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Expand Up @@ -149,3 +149,22 @@ Behavior in response to 5XX error:
</tr>
</tbody>
</table>

## Understand `no-store` and `no-cache` directives

There is often confusion between the directives `Cache-Control: no-store` and `Cache-Control: no-cache`, particularly regarding how they impact browser caching and features like the [Back-Forward Cache](https://developer.mozilla.org/en-US/docs/Glossary/bfcache) (BFCache).

### `no-store`

- Tells both browsers and intermediaries (like CDNs) not to store a copy of the response under any circumstance.
- The response is never written to disk or memory, which means the browser must fetch it again every time.
- In many browsers, `no-store` disables BFCache, because restoring a page from BFCache requires the browser to keep a copy of the page's memory state, which contradicts the “do not store” directive.
- This directive is used for highly sensitive or dynamic data (for example, banking apps, personal information, secure dashboards).

### `no-cache`

- Allows storing of the response (in both browser and intermediate caches), but requires revalidation with the origin server before using it.
- This ensures the content is always up-to-date, while still potentially allowing BFCache or other forms of performance optimization.
- This directive is used for data that changes frequently but is not sensitive, and can be served faster if validated rather than re-downloaded.

For more information about how these directives behave when Origin Cache Control is enabled or disabled refer to the [Directives](/cache/concepts/cache-control/#directives) section.