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Proxy servers sit between you and your internet connection, often caching or filtering the content as it makes its way from server to you.

When I configure various internet applications, they often ask for something called a "Proxy Server". I've apparently never needed it, since everything seems to work without configuring a proxy server. But does have me wondering - just what is a proxy server?

A proxy is a stand-in for you - someone who does something on your behalf. A proxy server is a kind of stand in for your computer.

The questions that raises of course would be how, and ... why?

A good example, and the one you probably see the most, is a web proxy. When configured to use a proxy, your web browser contacts the proxy server for each web access instead of going directly to the target server on the internet. The proxy server then turns around and makes the "real" request of the web server. The proxy server gets the response, and then passes it back to you.

So why go through that extra layer?

A proxy server is designed to understand, and act on the data that's going across it. For example a company's web proxy server might be where access to certain sites is blocked. It might track the surfing activities of employees or scan the returned web pages for viruses.

A proxy also hides the computers behind it. For example a company's web proxy may look like only one or two machines to the outside world, but in fact there may be several hundred employees surfing the web through it.

Proxy servers can also cache data. If everyone behind a proxy is requesting the same data over and over again, a proxy might elect to keep a local copy, and not bother getting it from the internet for every request.

Since you might also be wondering, some of the functions of a proxy are similar to a NAT router or a firewall. The biggest of several differences is that a proxy server actually understands the data that it's acting on. NAT routers and firewalls typically only understand details of where the data is going to or coming from, but not what it contains.

As you've already noticed, in most cases proxy servers are not used by typical internet users. There are certain situations ... usually corporate, and certain ISPs that require their use. The good news is that it's uncommon enough that if you do require it, it should be part of the setup information provided by your company or ISP.

Article C2407 - August 18, 2005 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

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38 Comments
wafaa
September 9, 2005 10:14 AM

hi,
i just want to ask you to tell how to use a proxy server to fool a firewall. i mean how to use it so that i can access all the sites i want from my work palce for example?

Sreenivas K R
October 13, 2005 9:57 AM

Can proxy server become Firewall at certain occasions ?

Leo
October 13, 2005 10:26 AM

Definitely.

Rod
October 26, 2005 3:10 AM

Hi, I got a question...
What is proxy traffic? I was reading some search engine forums and they said that "proxy traffic" is "bad"...and that some of them block proxy traffic... how's that? how can you tell? what is it?
Thanks a lot, most useful site...

Leo
October 26, 2005 8:19 AM

It depends on what they're talking about - it could mean many things. You might need to ask in the specific forums.

scooby
November 4, 2005 9:31 AM

Hi how can i tell if iam behind a proxy server and how to get rid of it.

abbas
January 23, 2006 2:01 AM

TANKYOU

Becca
March 29, 2006 2:49 PM

MSN messenger will no longer load on my computer because it says "Your Proxy Server appears to be offline, or your proxy settings are invalid" how do I fix this situation as I have tried many things. Please help. Thanks

beca
May 1, 2006 7:28 AM

does anyone know any proxy servers like nethider.com n things like that!

Jay
July 24, 2006 12:40 AM

My msn keeps coming up with a troubleshoot window everytime i try and login in msn and it says it could be due to improper proxy or firewall settings can someone pls email me and tell me what this means and how i can just get msn back bcos i have tried many things and nothing worls that i hav tried. thnx

Chou
August 22, 2006 12:19 PM

How do you know if you are behind a proxy server?

Sunny
September 17, 2006 6:57 PM

By connecting through a proxy server does that mean that my ISP will only be able to traceroute my surfing activity up to the proxy server ?

thank you

chris
October 5, 2006 1:42 AM

i have a question i didnt find anywhere yet, how do i change my proxy? because i have to use a US proxy to view a video on the web and i cant watch it here in canada 10 miles away from us line...silly. anyway
thank for helping me!

shumais
October 18, 2006 3:17 PM

if i am behind a proxy server..such as in a university lan...then if i access my email such as hotmail....are my emails being stored on the proxy server...and can someone actually go through them later on???

Leo Notenboom
October 18, 2006 9:27 PM

Maybe. Some do, some don't.

Latara Curtis
October 19, 2006 8:02 AM

what does a proxy server do

Jarrett
October 24, 2006 12:45 PM

the best proxy i kno rite now is Kproxy

Steve
November 2, 2006 6:03 AM

Does Windows Server 2003 have a built-in Proxy Server? If so,how do I access it? Thanks.

sike
November 7, 2006 1:29 AM

It says my proxy server is offline when i try to log in.
Then it says take the test to see if your able to actually connect to the internet.
It then says, you can now successfully sign in to msn.
But doesnt.
Nothing works all because of this proxy server setting.
Can you please tell me how to fix this thing?
thanks.

mehmetarkin
November 13, 2006 12:30 PM

hi leo

how can I learn whats the my proxy server ip.? and
anyone controling my domain name. But I cant see it.

bamboo
June 2, 2007 3:14 AM

You can see what proxies you have by typing 'tracert 154.178.143.145' in DOS. Or you can use 'tracert http://www.address.com' A handy wee tip I read about in a PC magazine once along with 'ping'. Good stuff to know.

Alvin Rajiv Camar
July 27, 2007 1:37 AM

My friend said that I could enter blocked sites in my country if I change my proxy server to a foreign country's one? Is that true?

blade4198
September 22, 2007 9:51 AM

you gata help me. each time i go to gaiaonline.com it says im goin tof ast and i think it thinks im a bot. i went on help rooms and some girl bipassed it by using a proxy server (the gaia problem is getting very common) but pleas tell me how to download the proxy server to bipass it or find out how i can play gaia without downloading the proxy server. whatever you do, you jsut gata help me man! please.

if you can help ill like psot it all over enternet and thousands of people will be very happy.

my email is:
[Email Address Removed]

tes
November 5, 2007 5:59 AM

is it possible to turn off proxy server for a user not to be identified by the proxy server and search blocked sites.

charles tittle
November 19, 2007 10:56 AM

hi leo
i keep getting, applet encountered a programming error.
i clear the cache and relaunch firefox, then it tell me you may have a caching proxy between you and our web server how do i check the proxy setting for my browser?

james
December 27, 2007 4:19 AM

where is my proxy server, as i need it to allow my internet protection to work?

tany
November 28, 2008 3:22 PM

i disagree tony leo is very helpful thanks again beautiful leo muah

Zoro
February 15, 2009 8:42 AM

Whatever they report it is inconvinciebly one of the most outstanding up to date vpn tools. Can you provide more info on setup?

sofie
May 20, 2009 9:39 PM

are there any free mac applications that unblock proxys, like the ones used to block msn on school wifi or something like that?

Abhi
May 25, 2009 10:24 PM

Hello Leo,

How can we install Porxy on Netware server?

Thanks and Regards,
Abhi

http://dnscaching.info/
September 24, 2009 6:30 AM

If you need a web proxy, you will find it on:
http://dnscaching.info/

Caylynn
April 14, 2010 2:34 PM

How do you install this proxy server?

Cliff
July 21, 2010 1:52 AM

How can I allow a visitor who is using a proxy server, access to the internet via my domain?

william
September 29, 2010 4:16 PM

every timei try to play my game pirates online it say proxy server is mest up or somthing

Bill Richardson
January 30, 2012 2:27 PM

Proxy allows PM but no posts?

pappuram sharma
March 5, 2012 11:39 PM

How do you install this proxy server?

Gina
February 5, 2013 7:49 PM

Can a proxy server be harmful to my OS, Since it understands the information being sent?

Mark J
February 6, 2013 2:07 AM

@Gina
I assume you're talking about web proxies as proxy servers internal to a network should be able to be trusted. A web proxy server wouldn't be any more harmful to your OS than any other web site you visit. There may be some rogue ones that try to infect your computer with malware, but they are not dangerous in and of themselves.

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