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Caching refers to storing the server response in the client itself, so that a client need not make a server request for the same resource again and again. A server response should have information about how caching is to be done, so that a client caches the response for a time-period or never caches the server response.
Following are the headers which a server response can have in order to configure a client”s caching −
| Sr.No. | Header & Description |
|---|---|
|
1 |
Date Date and Time of the resource when it was created. |
|
2 |
Last Modified Date and Time of the resource when it was last modified. |
|
3 |
Cache-Control Primary header to control caching. |
|
4 |
Expires Expiration date and time of caching. |
|
5 |
Age Duration in seconds from when resource was fetched from the server. |
Cache-Control Header
Following are the details of a Cache-Control header −
| Sr.No. | Directive & Description |
|---|---|
|
1 |
Public Indicates that resource is cacheable by any component. |
|
2 |
Private Indicates that resource is cacheable only by the client and the server, no intermediary can cache the resource. |
|
3 |
no-cache/no-store Indicates that a resource is not cacheable. |
|
4 |
max-age Indicates the caching is valid up to max-age in seconds. After this, client has to make another request. |
|
5 |
must-revalidate Indication to server to revalidate resource if max-age has passed. |
Best Practices
-
Always keep static contents like images, CSS, JavaScript cacheable, with expiration date of 2 to 3 days.
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Never keep expiry date too high.
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Dynamic content should be cached for a few hours only.
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