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?
http browser caching cross-browser refresh Share Improve this question Follow edited Apr 9 “16 at 9:51
Krzysztof Krasoń 23k1414 gold badges7777 silver badges9999 bronze badges asked Dec 22 “08 at 2:00
Morgan ChengMorgan Cheng 65.6k6363 gold badges165165 silver badges223223 bronze badges 3 Add a comment |
6 Answers 6
Active Oldest Votes326Generally 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.Bạn đang xem: Ctrl f5 là gì
Share Improve this answer Follow edited Mar 11 “14 at 9:20
naXa 25.8k1414 gold badges153153 silver badges212212 bronze badges answered Dec 22 “08 at 2:10
dancavallarodancavallaro 12.5k77 gold badges3333 silver badges3333 bronze badges 4 Add a comment | 526It is up to the browser but they behave in similar ways.
Đang xem: Chính Xác Thì Ctrl + F5 Là Gì
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”.
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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.
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”.
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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.