Web cache: Difference between revisions

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{{short description|System for optimizing the Web}}

A '''web cache''' (or '''HTTP cache''') is a system for optimizing the World Wide Web. It is implemented both client-side and server-side. The caching of multimedia and other files can result in less overall delay when [[web browser|browsing]] the Web.<ref>{{Cite web |last=Fountis |first=Yorgos |date=4 May 2017 |title=How does the browser cache work? |url=https://pressidium.com/blog/2017/browser-cache-work/}}</ref><ref>{{Cite journal |last1=Messaoud |first1=S. |last2=Youssef |first2=H. |date=2009 |title=An analytical model for the performance evaluation of stack-based web cache replacement algorithms |url=https://onlinelibrary.wiley.com/doi/10.1002/dac.1036 |journal=International Journal of Communication Systems |language=en |volume=23 |pages=1–22 |doi=10.1002/dac.1036|s2cid=46507769 |url-access=subscription }}</ref>

==Parts of the system==

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A forward cache is a cache outside the [[web server]]'s network, e.g. in the client's [[web browser]], in an [[ISP]], or within a corporate network. A network-aware forward cache only caches heavily accessed items. A proxy server sitting between the client and web server can evaluate HTTP headers and choose whether to store web content.

A reverse cache sits in front of one or more web servers, accelerating requests from the Internet and reducing peak server load. This is usually a [[content delivery network]] (CDN) that retains copies of web content at various points throughout a network.

===HTTP options===

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==Legality==

In 1998, the [[Digital Millennium Copyright Act]] added rules to the United States Code (17 U.S.C. §: 512) that exempts system operators from copyright liability for the purposes of caching.

==Server-side software==

This is a list of server-side web caching software.

{| style="font-size: 85%; text-align: center; width: auto;" class="sortable wikitable"

|-

!rowspan="2"|Name

!colspan="3"|Operating system

!rowspan="2"|Forward<br />mode

!rowspan="2"|Reverse<br />mode

!rowspan="2"|License

|-

![[Microsoft Windows|Windows]]

![[Unix-like]]

!Other

|-

! scope="row" |[[Apache HTTP Server]]

| {{yes}}

| {{yes|OS X, Linux, Unix, FreeBSD, Solaris, Novell NetWare}}

| {{yes|OS/2, TPF, OpenVMS, eComStation}}

|{{Yes}}

|

| {{open source|[[Apache 2.0]]}}

|-

! scope="row" | [[aiScaler]] Dynamic Cache Control

| {{no}}

| {{yes|[[Linux]]}}

| {{no}}

|

|

| {{Proprietary}}

|-

! scope="row" | [[ApplianSys#CACHEbox|ApplianSys CACHEbox]]

| {{no}}

| {{yes|[[Linux]]}}

| {{no}}

|

|

| {{Proprietary}}

|-

! scope="row" | [[Blue Coat Systems|Blue Coat]] ProxySG

| {{no}}

| {{no}}

| {{yes2|SGOS}}

| {{Yes}}

| {{Yes}}

| {{Proprietary}}

|-

! scope="row" | [[Nginx]]

| {{yes}}

| {{yes|[[Linux]], [[BSD]], [[OS X]], [[Solaris (operating system)|Solaris]], [[AIX]], [[HP-UX]]}}

| {{yes}}

| {{Yes}}

| {{Yes}}

| {{open source|2-clause [[BSD licenses|BSD]]-like}}

|-

! scope="row" | [[Microsoft Forefront Threat Management Gateway]]

| {{yes}}

| {{no}}

| {{no}}

| {{Yes}}

| {{Yes}}

| {{Proprietary}}

|-

! scope="row" | [[Polipo]]

| {{yes}}

| {{yes|[[OS X]], [[Linux]], [[OpenWrt]], [[FreeBSD]]}}

| {{dunno}}

| {{Yes}}

| {{Yes}}

| {{open source|[[MIT License]]}}

|-

! scope="row" | [[Squid (software)|Squid]]

| {{yes}}

| {{yes|[[Linux]]}}

| {{dunno}}

| {{Yes}}

| {{Yes}}

| {{open source|[[GPL]]}}

|-

! scope="row" | [[Apache Traffic Server]]

| {{dunno}}

| {{yes|[[Linux]]}}

| {{dunno}}

| {{Yes}}

| {{Yes}}

| {{open source|[[Apache 2.0]]}}

|-

! scope="row" | Untangle

| {{no}}

| {{yes|[[Linux]]}}

| {{no}}

| {{Yes}}

| {{Yes}}

| {{Proprietary}}

|-

! scope="row" | [[Varnish (software)|Varnish]]

| {{no}}

| {{yes|[[Linux]]}}

| {{no}}

| {{Needs}} a VMOD

| {{Yes}}

| {{open source|[[BSD licenses|BSD]]}}

|-

! scope="row" | [[WinGate]]

| {{yes}}

| {{no}}

| {{no}}

| {{Yes}}

| {{Yes}}

| {{Proprietary}} (Free for 8 users)

|-

! scope="row" |Nuster

| {{no}}

| {{yes|[[Linux]]}}

| {{no}}

| {{Yes}}

| {{Yes}}

| {{open source|[[GPL]]}}

|-

![[McAfee]] Web Gateway

| {{no}}

| {{yes2|McAfee Linux Operating System}}

| {{no}}

| {{Yes}}

| {{Yes}}

| {{Proprietary}}

|}

== See also ==

* [[InterPlanetary File System]] - makes web caches redundant

* [[Cache Discovery Protocol]]

* [[Cache manifest in HTML5]]

* [[Content delivery network]]

* [[Harvest project]]

* [[Proxy server]]

* [[Web accelerator]]

*[[Search engine cache]]

== References ==