The cache
read-only property of the Request
interface contains the cache mode of the request. It controls how the request will interact with the browser's HTTP cache.
Syntax
var currentCacheMode = request.cache;
Value
A RequestCache
value. The available values are:
default
— The browser looks for a matching request in its HTTP cache.- If there is a match and it is fresh, it will be returned from the cache.
- If there is a match but it is stale, the browser will make a conditional request to the remote server. If the server indicates that the resource has not changed, it will be returned from the cache. Otherwise the resource will be downloaded from the server and the cache will be updated.
- If there is no match, the browser will make a normal request, and will update the cache with the downloaded resource.
no-store
— The browser fetches the resource from the remote server without first looking in the cache, and will not update the cache with the downloaded resource.reload
— The browser fetches the resource from the remote server without first looking in the cache, but then will update the cache with the downloaded resource.no-cache
— The browser looks for a matching request in its HTTP cache.- If there is a match, fresh or stale, the browser will make a conditional request to the remote server. If the server indicates that the resource has not changed, it will be returned from the cache. Otherwise the resource will be downloaded from the server and the cache will be updated.
- If there is no match, the browser will make a normal request, and will update the cache with the downloaded resource.
force-cache
— The browser looks for a matching request in its HTTP cache.- If there is a match, fresh or stale, it will be returned from the cache.
- If there is no match, the browser will make a normal request, and will update the cache with the downloaded resource.
only-if-cached
— The browser looks for a matching request in its HTTP cache.- If there is a match, fresh or stale, it will be returned from the cache.
- If there is no match, the browser will respond with a 504 Gateway timeout status.
"only-if-cached"
mode can only be used if the request'smode
is"same-origin"
. Cached redirects will be followed if the request'sredirect
property is"follow"
and the redirects do not violate the"same-origin"
mode.
Example
// Download a resource with cache busting, to bypass the cache // completely. fetch("some.json", {cache: "no-store"}) .then(function(response) { /* consume the response */ }); // Download a resource with cache busting, but update the HTTP // cache with the downloaded resource. fetch("some.json", {cache: "reload"}) .then(function(response) { /* consume the response */ }); // Download a resource with cache busting when dealing with a // properly configured server that will send the correct ETag // and Date headers and properly handle If-Modified-Since and // If-None-Match request headers, therefore we can rely on the // validation to guarantee a fresh response. fetch("some.json", {cache: "no-cache"}) .then(function(response) { /* consume the response */ }); // Download a resource with economics in mind! Prefer a cached // albeit stale response to conserve as much bandwidth as possible. fetch("some.json", {cache: "force-cache"}) .then(function(response) { /* consume the response */ }); // Naive stale-while-revalidate client-level implementation. // Prefer a cached albeit stale response; but update if it's too old. // AbortController and signal to allow better memory cleaning. // In reality; this would be a function that takes a path and a // reference to the controller since it would need to change the value let controller = new AbortController(); fetch("some.json", {cache: "only-if-cached", mode: "same-origin", signal: controller.signal}) .catch(e => e instanceof TypeError && e.message === "Failed to fetch" ? ({status: 504}) : // Workaround for chrome; which simply fails with a typeerror Promise.reject(e)) .then(res => { if (res.status === 504) { controller.abort() controller = new AbortController(); return fetch("some.json", {cache: "force-cache", mode: "same-origin", signal: controller.signal}) } const date = res.headers.get("date"), dt = date ? new Date(date).getTime() : 0 if (dt < (Date.now() - 86400000)) { // if older than 24 hours controller.abort() controller = new AbortController(); return fetch("some.json", {cache: "reload", mode: "same-origin", signal: controller.signal}) } // Other possible conditions if (dt < (Date.now() - 300000)) // If it's older than 5 minutes fetch("some.json", {cache: "no-cache", mode: "same-origin"}) // no cancellation or return value. return res }) .then(function(response) { /* consume the (possibly stale) response */ }) .catch(error => { /* Can be an AbortError/DOMError or a TypeError */ });
Specifications
Specification | Status | Comment |
---|---|---|
Fetch The definition of 'cache' in that specification. |
Living Standard | Initial definition |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
cache | Chrome Full support 64 | Edge Full support 14 | Firefox Full support 48 | IE No support No | Opera Full support 51 | Safari Full support 11 | WebView Android Full support 64 | Chrome Android Full support 64 | Firefox Android No support No | Opera Android Full support 47 | Safari iOS No support No | Samsung Internet Android Full support 9.0 |
only-if-cached | Chrome No support No | Edge No support No | Firefox Full support 50 | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Firefox Android No support No | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No |
Legend
- Full support
- Full support
- No support
- No support
- Experimental. Expect behavior to change in the future.
- Experimental. Expect behavior to change in the future.