Browser Caching of CSS files

Question

Quick question regarding CSS and the browser  I tried searching SO and found some similar posts  but nothing definitive   I use one or two CSS files in my web projects  These are referenced in the HEAD of my web pages  Once I hit one of my pages  does the CSS get cached so that it s not re-downloaded with each request  I hope so  Do IE  Firefox and Safari handle this differently  If the browser is closed  is the CSS refreshed on the first visit when a new browser instance is opened

User · Answer

It s probably worth noting that IE won t cache css files called by other css files using the  import method  So  for example  if your html page links to  master css  which pulls in  reset css  via  import  then reset css will not be cached by IE

User · Answer

Unless you ve messed with your server  yes it s cached   All the browsers are supposed to handle it the same   Some people  like me  might have their browsers configured so that it doesn t cache any files though   Closing the browser doesn t invalidate the file in the cache   Changing the file on the server should cause a refresh of the file however

User · Answer

It does depend on the HTTP headers sent with the CSS files as both of the previous answers state - as long as you don t append any cachebusting stuff to the href  e g      lt link href   stylesheets mycss css some var to bust cache 24312345  rel  stylesheet  type  text css    gt    Some frameworks  e g  rails  put these in by default   However If you get something like firebug or fiddler  you can see exactly what your browser is downloading on each request - which is expecially useful for finding out what your browser is doing  as opposed to just what it should be doing   All browsers should respect the cache headers in the same way  unless configured to ignore them  but there are bound to be exceptions

User · Answer

Your file will probably be cached - but it depends     Different browsers have slightly different behaviors - most noticeably when dealing with ambiguous limited caching headers emanating from the server  If you send a clear signal  the browsers obey  virtually all of the time   The greatest variance by far  is in the default caching configuration of different web servers and application servers   Some  e g  Apache  are likely to serve known static file types with HTTP headers encouraging the browser to cache them  while other servers may send no-cache commands with every response - regardless of filetype        So  first off  read some of the excellent HTTP caching tutorials out there  HTTP Caching  amp  Cache-Busting for Content Publishers was a real eye opener for me  -   Next install and fiddle around with Firebug and the Live HTTP Headers add-on   to find out which headers your server is actually sending   Then read your web server docs to find out how to tweak them to perfection  or talk your sysadmin into doing it for you         As to what happens when the browser is restarted  it depends on the browser and the user configuration   As a rule of thumb  expect the browser to be more likely to check in with the server after each restart  to see if anything has changed  see If-Last-Modified and If-None-Match    If you configure your server correctly  it should be able to return a super-short 304 Not Modified  costing very little bandwidth  and after that the browser will use the cache as normal

User · Answer

It does depend on the HTTP headers sent with the CSS files as both of the previous answers state - as long as you don t append any cachebusting stuff to the href  e g      lt link href   stylesheets mycss css some var to bust cache 24312345  rel  stylesheet  type  text css    gt    Some frameworks  e g  rails  put these in by default   However If you get something like firebug or fiddler  you can see exactly what your browser is downloading on each request - which is expecially useful for finding out what your browser is doing  as opposed to just what it should be doing   All browsers should respect the cache headers in the same way  unless configured to ignore them  but there are bound to be exceptions

User · Answer

Your file will probably be cached - but it depends     Different browsers have slightly different behaviors - most noticeably when dealing with ambiguous limited caching headers emanating from the server  If you send a clear signal  the browsers obey  virtually all of the time   The greatest variance by far  is in the default caching configuration of different web servers and application servers   Some  e g  Apache  are likely to serve known static file types with HTTP headers encouraging the browser to cache them  while other servers may send no-cache commands with every response - regardless of filetype        So  first off  read some of the excellent HTTP caching tutorials out there  HTTP Caching  amp  Cache-Busting for Content Publishers was a real eye opener for me  -   Next install and fiddle around with Firebug and the Live HTTP Headers add-on   to find out which headers your server is actually sending   Then read your web server docs to find out how to tweak them to perfection  or talk your sysadmin into doing it for you         As to what happens when the browser is restarted  it depends on the browser and the user configuration   As a rule of thumb  expect the browser to be more likely to check in with the server after each restart  to see if anything has changed  see If-Last-Modified and If-None-Match    If you configure your server correctly  it should be able to return a super-short 304 Not Modified  costing very little bandwidth  and after that the browser will use the cache as normal

User · Answer

To the first part of your question - yes  browsers cache css files  if this is not disabled by browser s configuration   Many browsers have key combination to reload a page without a cache  If you made changes to css and want users to see them immediately instead of waiting next time when browser reloads the files without caching  you can change the way CSS ir served by adding some parameters to the url like this    style css modified 20012009

User · Answer

That depends on what headers you are sending along with your CSS files  Check your server configuration as you are probably not sending them manually  Do a google search for  http caching  to learn about different caching options you can set  You can force the browser to download a fresh copy of the file everytime it loads it for instance  or you can cache the file for one week

User · Answer

It does depend on the HTTP headers sent with the CSS files as both of the previous answers state - as long as you don t append any cachebusting stuff to the href  e g      lt link href   stylesheets mycss css some var to bust cache 24312345  rel  stylesheet  type  text css    gt    Some frameworks  e g  rails  put these in by default   However If you get something like firebug or fiddler  you can see exactly what your browser is downloading on each request - which is expecially useful for finding out what your browser is doing  as opposed to just what it should be doing   All browsers should respect the cache headers in the same way  unless configured to ignore them  but there are bound to be exceptions

User · Answer

It s probably worth noting that IE won t cache css files called by other css files using the  import method  So  for example  if your html page links to  master css  which pulls in  reset css  via  import  then reset css will not be cached by IE

User · Answer

That depends on what headers you are sending along with your CSS files  Check your server configuration as you are probably not sending them manually  Do a google search for  http caching  to learn about different caching options you can set  You can force the browser to download a fresh copy of the file everytime it loads it for instance  or you can cache the file for one week

User · Answer

To the first part of your question - yes  browsers cache css files  if this is not disabled by browser s configuration   Many browsers have key combination to reload a page without a cache  If you made changes to css and want users to see them immediately instead of waiting next time when browser reloads the files without caching  you can change the way CSS ir served by adding some parameters to the url like this    style css modified 20012009

User · Answer

That depends on what headers you are sending along with your CSS files  Check your server configuration as you are probably not sending them manually  Do a google search for  http caching  to learn about different caching options you can set  You can force the browser to download a fresh copy of the file everytime it loads it for instance  or you can cache the file for one week

User · Answer

To the first part of your question - yes  browsers cache css files  if this is not disabled by browser s configuration   Many browsers have key combination to reload a page without a cache  If you made changes to css and want users to see them immediately instead of waiting next time when browser reloads the files without caching  you can change the way CSS ir served by adding some parameters to the url like this    style css modified 20012009

User · Answer

That depends on what headers you are sending along with your CSS files  Check your server configuration as you are probably not sending them manually  Do a google search for  http caching  to learn about different caching options you can set  You can force the browser to download a fresh copy of the file everytime it loads it for instance  or you can cache the file for one week

User · Answer

Unless you ve messed with your server  yes it s cached   All the browsers are supposed to handle it the same   Some people  like me  might have their browsers configured so that it doesn t cache any files though   Closing the browser doesn t invalidate the file in the cache   Changing the file on the server should cause a refresh of the file however

User · Answer

Unless you ve messed with your server  yes it s cached   All the browsers are supposed to handle it the same   Some people  like me  might have their browsers configured so that it doesn t cache any files though   Closing the browser doesn t invalidate the file in the cache   Changing the file on the server should cause a refresh of the file however

User · Answer

It does depend on the HTTP headers sent with the CSS files as both of the previous answers state - as long as you don t append any cachebusting stuff to the href  e g      lt link href   stylesheets mycss css some var to bust cache 24312345  rel  stylesheet  type  text css    gt    Some frameworks  e g  rails  put these in by default   However If you get something like firebug or fiddler  you can see exactly what your browser is downloading on each request - which is expecially useful for finding out what your browser is doing  as opposed to just what it should be doing   All browsers should respect the cache headers in the same way  unless configured to ignore them  but there are bound to be exceptions

User · Answer

It s probably worth noting that IE won t cache css files called by other css files using the  import method  So  for example  if your html page links to  master css  which pulls in  reset css  via  import  then reset css will not be cached by IE

User · Answer

Your file will probably be cached - but it depends     Different browsers have slightly different behaviors - most noticeably when dealing with ambiguous limited caching headers emanating from the server  If you send a clear signal  the browsers obey  virtually all of the time   The greatest variance by far  is in the default caching configuration of different web servers and application servers   Some  e g  Apache  are likely to serve known static file types with HTTP headers encouraging the browser to cache them  while other servers may send no-cache commands with every response - regardless of filetype        So  first off  read some of the excellent HTTP caching tutorials out there  HTTP Caching  amp  Cache-Busting for Content Publishers was a real eye opener for me  -   Next install and fiddle around with Firebug and the Live HTTP Headers add-on   to find out which headers your server is actually sending   Then read your web server docs to find out how to tweak them to perfection  or talk your sysadmin into doing it for you         As to what happens when the browser is restarted  it depends on the browser and the user configuration   As a rule of thumb  expect the browser to be more likely to check in with the server after each restart  to see if anything has changed  see If-Last-Modified and If-None-Match    If you configure your server correctly  it should be able to return a super-short 304 Not Modified  costing very little bandwidth  and after that the browser will use the cache as normal

User · Answer

It s probably worth noting that IE won t cache css files called by other css files using the  import method  So  for example  if your html page links to  master css  which pulls in  reset css  via  import  then reset css will not be cached by IE

User · Answer

Your file will probably be cached - but it depends     Different browsers have slightly different behaviors - most noticeably when dealing with ambiguous limited caching headers emanating from the server  If you send a clear signal  the browsers obey  virtually all of the time   The greatest variance by far  is in the default caching configuration of different web servers and application servers   Some  e g  Apache  are likely to serve known static file types with HTTP headers encouraging the browser to cache them  while other servers may send no-cache commands with every response - regardless of filetype        So  first off  read some of the excellent HTTP caching tutorials out there  HTTP Caching  amp  Cache-Busting for Content Publishers was a real eye opener for me  -   Next install and fiddle around with Firebug and the Live HTTP Headers add-on   to find out which headers your server is actually sending   Then read your web server docs to find out how to tweak them to perfection  or talk your sysadmin into doing it for you         As to what happens when the browser is restarted  it depends on the browser and the user configuration   As a rule of thumb  expect the browser to be more likely to check in with the server after each restart  to see if anything has changed  see If-Last-Modified and If-None-Match    If you configure your server correctly  it should be able to return a super-short 304 Not Modified  costing very little bandwidth  and after that the browser will use the cache as normal

User · Answer

To the first part of your question - yes  browsers cache css files  if this is not disabled by browser s configuration   Many browsers have key combination to reload a page without a cache  If you made changes to css and want users to see them immediately instead of waiting next time when browser reloads the files without caching  you can change the way CSS ir served by adding some parameters to the url like this    style css modified 20012009

User · Answer

Unless you ve messed with your server  yes it s cached   All the browsers are supposed to handle it the same   Some people  like me  might have their browsers configured so that it doesn t cache any files though   Closing the browser doesn t invalidate the file in the cache   Changing the file on the server should cause a refresh of the file however

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