What requests do browsers F5 and Ctrl F5 refreshes generate

Question

Is there a standard for what actions F5 and Ctrl   F5 trigger in web browsers   I once did experiment in IE6 and Firefox 2 x  The F5  refresh would trigger a HTTP request sent to the server with an If-Modified-Since header  while Ctrl   F5 would not have such a header  In my understanding  F5  will try to utilize cached content as much as possible  while Ctrl   F5  is intended to abandon all cached content and just retrieve all content from the servers again    But today  I noticed that in some of the latest browsers  Chrome  IE8  it doesn t work in this way anymore  Both F5 and Ctrl   F5 send the If-Modified-Since header    So how is this supposed to work  or  if there is no standard  how do the major browsers differ in how they implement these refresh features

User · Answer

IE7 8 9 seem to behave differently depending on whether the page has focus or not    If you click on the page and CTRL F5 then  Cache-Control  no-cache  is included in the request headers  If you click in the Location Address bar then press CTRL F5 it isn t

User · Answer

It is up to the browser but they behave in similar ways   I have tested FF  IE7  Opera and Chrome   F5 usually updates the page only if it is modified  The browser usually tries to use all types of cache as much as possible and adds an  If-modified-since  header to the request  Opera differs by sending a  Cache-Control  no-cache    CTRL-F5 is used to force an update  disregarding any cache  IE7 adds an  Cache-Control  no-cache   as does FF  which also adds  Pragma  no-cache   Chrome does a normal  If-modified-since  and Opera ignores the key    If I remember correctly it was Netscape which was the first browser to add support for cache-control by adding  Pragma  No-cache  when you pressed CTRL-F5   Edit  Updated table  The table below is updated with information on what will happen when the browser s refresh-button is clicked  after a request by Joel Coehoorn   and the  max-age 0  Cache-control-header   Updated table  27 September 2010   ------------------------------------------------------------      UPDATED                     Firefox 3 x                         27 SEP 2010      --------------------------------------------                                    MSIE 8  7                            Version 3           -----------------------------------------                                     Chrome 6 0                                                   --------------------------------------                                      Chrome 1 0                                                       -----------------------------------                                       Opera 10  9                                                          --------------------------------                                                                           ------------ -- -- -- -- -- --------------------------------               F5  IM  I   IM  IM  C                                            SHIFT-F5  -   -   CP  IM  -    Legend                                   CTRL-F5  CP  C   CP  IM  -    I    If-Modified-Since                    ALT-F5  -   -   -   -    2   P    Pragma  No-cache                   ALTGR-F5  -   I   -   -   -    C    Cache-Control  no-cache       ------------ -- -- -- -- --   M    Cache-Control  max-age 0             CTRL-R  IM  I   IM  IM  C    -   ignored                         CTRL-SHIFT-R  CP  -   CP  -   -                                       ------------ -- -- -- -- --                                              Click  IM  I   IM  IM  C    With  click  I refer to a            Shift-Click  CP  I   CP  IM  C    mouse click on the browsers           Ctrl-Click   1  C   CP  IM  C    refresh-icon                           Alt-Click  IM  I   IM  IM  C                                         AltGr-Click  IM  I   -   IM  -                                       ------------------------------------------------------------    Versions tested    Firefox 3 1 6 and 3 0 6  WINXP  MSIE 8 0 6001 and 7 0 5730 11  WINXP  Chrome 6 0 472 63 and 1 0 151 48  WINXP  Opera 10 62 and 9 61  WINXP    Notes    Version 3 0 6 sends I and C  but 3 1 6 opens the page in a new tab  making a normal request with only  I   Version 10 62 does nothing  9 61 might do C unless it was a typo in my old table    Note about Chrome 6 0 472  If you do a forced reload  like CTRL-F5  it behaves like the url is internally marked to always do a forced reload  The flag is cleared if you go to the address bar and press enter

User · Answer

When user press F5 although new request goes to web server and get a responce for the request as well  But when the responce header is Parsed it check the required information in browser cache  If the required information in cache has not expired then that information is restored from in cache itself   When user click on CTRL-F5 even then new request goes to web server and get a responce  But this time when the responce header is Parsed it do not check any required information in cache  and bring all updated information form server only

User · Answer

It is up to the browser but they behave in similar ways   I have tested FF  IE7  Opera and Chrome   F5 usually updates the page only if it is modified  The browser usually tries to use all types of cache as much as possible and adds an  If-modified-since  header to the request  Opera differs by sending a  Cache-Control  no-cache    CTRL-F5 is used to force an update  disregarding any cache  IE7 adds an  Cache-Control  no-cache   as does FF  which also adds  Pragma  no-cache   Chrome does a normal  If-modified-since  and Opera ignores the key    If I remember correctly it was Netscape which was the first browser to add support for cache-control by adding  Pragma  No-cache  when you pressed CTRL-F5   Edit  Updated table  The table below is updated with information on what will happen when the browser s refresh-button is clicked  after a request by Joel Coehoorn   and the  max-age 0  Cache-control-header   Updated table  27 September 2010   ------------------------------------------------------------      UPDATED                     Firefox 3 x                         27 SEP 2010      --------------------------------------------                                    MSIE 8  7                            Version 3           -----------------------------------------                                     Chrome 6 0                                                   --------------------------------------                                      Chrome 1 0                                                       -----------------------------------                                       Opera 10  9                                                          --------------------------------                                                                           ------------ -- -- -- -- -- --------------------------------               F5  IM  I   IM  IM  C                                            SHIFT-F5  -   -   CP  IM  -    Legend                                   CTRL-F5  CP  C   CP  IM  -    I    If-Modified-Since                    ALT-F5  -   -   -   -    2   P    Pragma  No-cache                   ALTGR-F5  -   I   -   -   -    C    Cache-Control  no-cache       ------------ -- -- -- -- --   M    Cache-Control  max-age 0             CTRL-R  IM  I   IM  IM  C    -   ignored                         CTRL-SHIFT-R  CP  -   CP  -   -                                       ------------ -- -- -- -- --                                              Click  IM  I   IM  IM  C    With  click  I refer to a            Shift-Click  CP  I   CP  IM  C    mouse click on the browsers           Ctrl-Click   1  C   CP  IM  C    refresh-icon                           Alt-Click  IM  I   IM  IM  C                                         AltGr-Click  IM  I   -   IM  -                                       ------------------------------------------------------------    Versions tested    Firefox 3 1 6 and 3 0 6  WINXP  MSIE 8 0 6001 and 7 0 5730 11  WINXP  Chrome 6 0 472 63 and 1 0 151 48  WINXP  Opera 10 62 and 9 61  WINXP    Notes    Version 3 0 6 sends I and C  but 3 1 6 opens the page in a new tab  making a normal request with only  I   Version 10 62 does nothing  9 61 might do C unless it was a typo in my old table    Note about Chrome 6 0 472  If you do a forced reload  like CTRL-F5  it behaves like the url is internally marked to always do a forced reload  The flag is cleared if you go to the address bar and press enter

User · Answer

Generally speaking   F5 may give you the same page even if the content is changed  because it may load the page from cache  But Ctrl-F5 forces a cache refresh  and will guarantee that if the content is changed  you will get the new content

User · Answer

At least in Firefox  v3 5   cache seems to be disabled rather than simply cleared  If there are multiple instances of the same image on a page  it will be transferred multiple times  That is also the case for img tags that are added subsequently via Ajax JavaScript   So in case you re wondering why the browser keeps downloading the same little icon a few hundred times on your auto-refresh Ajax site  it s because you initially loaded the page using CTRL-F5

User · Answer

When user press F5 although new request goes to web server and get a responce for the request as well  But when the responce header is Parsed it check the required information in browser cache  If the required information in cache has not expired then that information is restored from in cache itself   When user click on CTRL-F5 even then new request goes to web server and get a responce  But this time when the responce header is Parsed it do not check any required information in cache  and bring all updated information form server only

User · Answer

I ve implemented cross-browser compatible page to test browser s refresh behavior  here is the source code  and get results similar to  some  but for modern browsers

User · Answer

IE7 8 9 seem to behave differently depending on whether the page has focus or not    If you click on the page and CTRL F5 then  Cache-Control  no-cache  is included in the request headers  If you click in the Location Address bar then press CTRL F5 it isn t

User · Answer

I ve implemented cross-browser compatible page to test browser s refresh behavior  here is the source code  and get results similar to  some  but for modern browsers

User · Answer

It is up to the browser but they behave in similar ways   I have tested FF  IE7  Opera and Chrome   F5 usually updates the page only if it is modified  The browser usually tries to use all types of cache as much as possible and adds an  If-modified-since  header to the request  Opera differs by sending a  Cache-Control  no-cache    CTRL-F5 is used to force an update  disregarding any cache  IE7 adds an  Cache-Control  no-cache   as does FF  which also adds  Pragma  no-cache   Chrome does a normal  If-modified-since  and Opera ignores the key    If I remember correctly it was Netscape which was the first browser to add support for cache-control by adding  Pragma  No-cache  when you pressed CTRL-F5   Edit  Updated table  The table below is updated with information on what will happen when the browser s refresh-button is clicked  after a request by Joel Coehoorn   and the  max-age 0  Cache-control-header   Updated table  27 September 2010   ------------------------------------------------------------      UPDATED                     Firefox 3 x                         27 SEP 2010      --------------------------------------------                                    MSIE 8  7                            Version 3           -----------------------------------------                                     Chrome 6 0                                                   --------------------------------------                                      Chrome 1 0                                                       -----------------------------------                                       Opera 10  9                                                          --------------------------------                                                                           ------------ -- -- -- -- -- --------------------------------               F5  IM  I   IM  IM  C                                            SHIFT-F5  -   -   CP  IM  -    Legend                                   CTRL-F5  CP  C   CP  IM  -    I    If-Modified-Since                    ALT-F5  -   -   -   -    2   P    Pragma  No-cache                   ALTGR-F5  -   I   -   -   -    C    Cache-Control  no-cache       ------------ -- -- -- -- --   M    Cache-Control  max-age 0             CTRL-R  IM  I   IM  IM  C    -   ignored                         CTRL-SHIFT-R  CP  -   CP  -   -                                       ------------ -- -- -- -- --                                              Click  IM  I   IM  IM  C    With  click  I refer to a            Shift-Click  CP  I   CP  IM  C    mouse click on the browsers           Ctrl-Click   1  C   CP  IM  C    refresh-icon                           Alt-Click  IM  I   IM  IM  C                                         AltGr-Click  IM  I   -   IM  -                                       ------------------------------------------------------------    Versions tested    Firefox 3 1 6 and 3 0 6  WINXP  MSIE 8 0 6001 and 7 0 5730 11  WINXP  Chrome 6 0 472 63 and 1 0 151 48  WINXP  Opera 10 62 and 9 61  WINXP    Notes    Version 3 0 6 sends I and C  but 3 1 6 opens the page in a new tab  making a normal request with only  I   Version 10 62 does nothing  9 61 might do C unless it was a typo in my old table    Note about Chrome 6 0 472  If you do a forced reload  like CTRL-F5  it behaves like the url is internally marked to always do a forced reload  The flag is cleared if you go to the address bar and press enter

User · Answer

It is up to the browser but they behave in similar ways   I have tested FF  IE7  Opera and Chrome   F5 usually updates the page only if it is modified  The browser usually tries to use all types of cache as much as possible and adds an  If-modified-since  header to the request  Opera differs by sending a  Cache-Control  no-cache    CTRL-F5 is used to force an update  disregarding any cache  IE7 adds an  Cache-Control  no-cache   as does FF  which also adds  Pragma  no-cache   Chrome does a normal  If-modified-since  and Opera ignores the key    If I remember correctly it was Netscape which was the first browser to add support for cache-control by adding  Pragma  No-cache  when you pressed CTRL-F5   Edit  Updated table  The table below is updated with information on what will happen when the browser s refresh-button is clicked  after a request by Joel Coehoorn   and the  max-age 0  Cache-control-header   Updated table  27 September 2010   ------------------------------------------------------------      UPDATED                     Firefox 3 x                         27 SEP 2010      --------------------------------------------                                    MSIE 8  7                            Version 3           -----------------------------------------                                     Chrome 6 0                                                   --------------------------------------                                      Chrome 1 0                                                       -----------------------------------                                       Opera 10  9                                                          --------------------------------                                                                           ------------ -- -- -- -- -- --------------------------------               F5  IM  I   IM  IM  C                                            SHIFT-F5  -   -   CP  IM  -    Legend                                   CTRL-F5  CP  C   CP  IM  -    I    If-Modified-Since                    ALT-F5  -   -   -   -    2   P    Pragma  No-cache                   ALTGR-F5  -   I   -   -   -    C    Cache-Control  no-cache       ------------ -- -- -- -- --   M    Cache-Control  max-age 0             CTRL-R  IM  I   IM  IM  C    -   ignored                         CTRL-SHIFT-R  CP  -   CP  -   -                                       ------------ -- -- -- -- --                                              Click  IM  I   IM  IM  C    With  click  I refer to a            Shift-Click  CP  I   CP  IM  C    mouse click on the browsers           Ctrl-Click   1  C   CP  IM  C    refresh-icon                           Alt-Click  IM  I   IM  IM  C                                         AltGr-Click  IM  I   -   IM  -                                       ------------------------------------------------------------    Versions tested    Firefox 3 1 6 and 3 0 6  WINXP  MSIE 8 0 6001 and 7 0 5730 11  WINXP  Chrome 6 0 472 63 and 1 0 151 48  WINXP  Opera 10 62 and 9 61  WINXP    Notes    Version 3 0 6 sends I and C  but 3 1 6 opens the page in a new tab  making a normal request with only  I   Version 10 62 does nothing  9 61 might do C unless it was a typo in my old table    Note about Chrome 6 0 472  If you do a forced reload  like CTRL-F5  it behaves like the url is internally marked to always do a forced reload  The flag is cleared if you go to the address bar and press enter

User · Answer

Generally speaking   F5 may give you the same page even if the content is changed  because it may load the page from cache  But Ctrl-F5 forces a cache refresh  and will guarantee that if the content is changed  you will get the new content

User · Answer

Generally speaking   F5 may give you the same page even if the content is changed  because it may load the page from cache  But Ctrl-F5 forces a cache refresh  and will guarantee that if the content is changed  you will get the new content

User · Answer

At least in Firefox  v3 5   cache seems to be disabled rather than simply cleared  If there are multiple instances of the same image on a page  it will be transferred multiple times  That is also the case for img tags that are added subsequently via Ajax JavaScript   So in case you re wondering why the browser keeps downloading the same little icon a few hundred times on your auto-refresh Ajax site  it s because you initially loaded the page using CTRL-F5

User · Answer

Generally speaking   F5 may give you the same page even if the content is changed  because it may load the page from cache  But Ctrl-F5 forces a cache refresh  and will guarantee that if the content is changed  you will get the new content

[http] What requests do browsers' "F5" and "Ctrl + F5" refreshes generate?

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