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

http browser caching cross-browser refresh

599,519

Solution 1

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.

Solution 2

It is up to the browser but they behave in similar ways.

F5 usually updates the page only if it is modified. Modern browsers sends Cache-Control: max-age=0 to tell any cache the maximum amount of time a resource is considered fresh, relative to the time of the request.

CTRL-F5 is used to force an update, disregarding any cache. Modern browsers sends Cache-Control: no-cache and Pragma: No-cache

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.

┌───────────┬──────────────┬─────┬─────────────────┬──────────────────────────────┐
│ Version 4 │      F5      │  R  │      CLICK      │ Legend:                      │
│2021 MAY 19├──┬──┬──┬──┬──┼──┬──┼──┬──┬──┬──┬──┬──┤ C = Cache-Control: no-cache  │
│           │  │S │C │A │A │C │C │  │S │C │A │A │C │ I = If-Modified-Since        │
│           │  │H │T │L │L │T │T │  │H │T │L │L │T │ M = Cache-Control: max-age=0 │
│           │  │I │R │T │T │R │R │  │I │R │T │T │R │ N = Not tested               │
│           │  │F │L │  │G │L │L │  │F │L │  │G │L │ P = Pragma: No-cache         │
│           │  │T │  │  │R │  │+ │  │T │  │  │R │+ │ - = ignored                  │
│           │  │  │  │  │  │  │S │  │  │  │  │  │S │                              │
│           │  │  │  │  │  │  │H │  │  │  │  │  │H │ With 'CLICK' I refer to a    │
│           │  │  │  │  │  │  │I │  │  │  │  │  │I │ mouse click on the browsers  │
│           │  │  │  │  │  │  │F │  │  │  │  │  │F │ refresh-icon.                │
│           │  │  │  │  │  │  │T │  │  │  │  │  │T │                              │
│           │  │  │  │  │  │  │  │  │  │  │  │  │  │ 1: Version 3.0.6 sends I     │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤    and C, but 3.1.6 opens    │
│Brave 1.24 │M │CP│CP│- │- │M │CP│M │CP│CP│M │CP│CP│    the page in a new tab,    │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤    making a normal request   │
│Chrome 1   │MI│MI│MI│- │- │MI│- │MI│MI│MI│MI│MI│N │    with only I.              │
│Chrome 6   │MI│CP│CP│- │- │MI│CP│MI│CP│CP│MI│- │N │ 2: Version 10.62 does        │
│Chrome 90  │M │CP│CP│- │- │M │CP│M │CP│CP│M │CP│CP│    nothing. 9.61 might do C  │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤    unless it was a typo in   │
│Edge 90    │M │CP│CP│- │- │M │CP│M │CP│CP│M │CP│CP│    my old table.             │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤ 3: Opens the currernt tab in │
│Firefox 3.x│MI│- │CP│- │- │MI│CP│MI│CP│1 │M │MI│N │    a new tab, but does not   │
│Firefox 89 │M │- │CP│- │M │M │CP│M │CP│3 │M │M │3 │    refresh the page if it is │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤    cached in the browser.    │
│MSIE 8, 7  │I │- │C │- │I │I │  │I │I │C │I │I │N │                              │
├───────────┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┼──┤                              │
│Opera 10, 9│C │- │- │2 │- │C │- │C │C │C │C │- │N │                              │
│Opera 76   │M │CP│CP│- │- │M │- │M │CP│CP│M │CP│CP│                              │
├───────────┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──┴──────────────────────────────┤
│                    https://stackoverflow.com/a/385491/36866                     │
└─────────────────────────────────────────────────────────────────────────────────┘

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.

Solution 3

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:

enter image description here

Solution 4

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.

Solution 5

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.

View more solutions

599,519

Author by

Morgan Cheng

I am a software engineer in China. This is my Blog ??????????,??????

Updated on July 17, 2021

Comments

Morgan Cheng almost 3 years

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?
Joel Coehoorn about 15 years

Any chance you could add SHIFT-ClickRefreshButton to this table?
Joel Coehoorn about 15 years

BTW: Very nice job color-coding the key like that.
some about 15 years

@Joel Coehoorn: Updated the table with click on the refresh button. Got to love ASCII graphic tables, don't you? The color-coding was is just a side-effect of the code color-coding.
John Topley about 15 years

Can't you do it as a proper HTML table?
Kip over 14 years

FYI - this answer has actually been referenced on the chrome development/bug tracking boards: code.google.com/p/chromium/issues/detail?id=1906
some over 13 years

@Kyle: Thanks for correcting my spelling. @Kip: Thank you very much for the information about the chrome bug tracking. That made my day!
some over 13 years

@John Topley: Tables isn't allowed, so the answer is no.
cburgmer almost 13 years

Great work on this table - this belongs on quirksmode. +1. I wonder if there's also variation in what headers are used to request resources within the refreshed page, such as images, stylesheets, etc...
some almost 13 years

@James Hart: Thank you! This is the result I got after testing with a html document with an external script, css and image: For FF (4.0.1@win32) and MSIE(8.0.6001.18702@win32) it's the same type of request. Chrome (11.0.696.68@win32) also does the same, but if you force a reload (CTRL-F5) it behaves like an internal flag is set and if you press F5 again the HTML-document is retrieved with MP and all other with IM. Se the note above in the answer. Opera (11.01 1190@win32) does C for the HTML-document and I for the included resources.
Paul Irish almost 13 years

I believe Chrome has updated its shift-refresh behavior as of 11 or 12 or so. Could we can get an update? Thanks!
some almost 13 years

@Paul Irish: I will check if they have changed it in a few days. BTW you noticed the note about chrome 6?
Ruan Mendes almost 12 years

The links on your page are broken, I fixed the link on the answer, but a lot of the links from that page are broken. podlipensky.com/examples/refreshbutton/index.html , podlipensky.com/post/2012/02/27/…
Pavel Podlipensky almost 12 years

Sorry, about that - doing blog migration. Links will be fixed ASAP, for now - please go to github repository and download examples.
AaronLS over 11 years

Thi is accurate, but note that while Ctrl+F5 will cause the browser to throw out the cache and request a new from the server, the server may ignore the no-cache header and serve a server side cached page. Thus even Ctrl+F5 may return an old version of the page if the server ignores the no-cache header.
bernardn over 9 years

The links are still broken. Migration not finished?
Dimitri Dewaele over 9 years

F5 wil refresh the page - CTRL+F5 will do 'hard' refresh.
jawo over 8 years

Also mention, that Ctrl-F5 will submit a form, if given.
Greg Dubicki over 8 years

Can you please update your answer with current version of the browsers, especially mobile and desktop Safari, @PavelPodlipensky?
molerus over 7 years

Ok, so if you hit ctrl+f5 you tell your browser not to use its cache, but what happens in subsequent requests to the same page? I mean, can you see older versions of the page after you´ve seen the oldest one? If i´m seeing version 1 of the page because its cached but theres already version 2 available, i understand that hitting ctrl+f5 will make me see version2. Then i close my browser and open that page again, ¿do i see version 1 or i still see version2? Thanks.
some about 3 years

@PaulIrish 10 years later, the table is updated. :)