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Title text: The hardest refresh requires both a Mac keyboard and a Windows keyboard as a security measure, like how missile launch systems require two keys to be turned at once.
In this comic Randall presents five different levels of refresh operations for web applications. The first three (soft refresh, normal refresh, and hard refresh) are common operations to keep the content in the browser retrieved from the server up to date. The other two (harder refresh and hardest refresh) are fictional operations to perform refresh operations on remote resources. The terms are probably adopted from soft and hard reset operations used to restart broken computers or e.g. smartphones.
The normal refresh is a browser operation that reloads the complete web page, text and other content that has changed since the original load will be updated. The operation can be triggered by refresh buttons in browsers, though it also can be requested using the common keyboard commands as listed by Randall. Many pages -- like the main page at xkcd.com -- don't have a refresh button, but pressing the F5-key after a new comic is released is will be shown in the browser.
What Randall calls hard refresh is a less common browser operation but sometimes needed to ensure that every content is completely new retrieved from the server. Everything in the browser cache is ignored and updated by the new response from the server, regardless if it's new or not. Browser caching is a way to store webpage resources locally in order to decrease the load time and the amount of data to receive. This is slower because it forces the browser to download the entire page, it ensures that the page is displayed as it is currently being served. Hard refreshes are usually used when a web application has changed in such a way that the cached data is interfering with the proper display of the page.
If there is a Web-Proxy or a Cloud-Cache (like used for this wiki) in the middle between the browser and the Web-Server this type of refreshing may not work. In this case the user has to wait until the cache entry is expired and a new request to the web server is done. A Web-developer may try to avoid this behave by including special meta-tags in the HTML header to suppress caching, but not all proxies or clouds follow these instructions.
Harder refresh is a joke that extends the existing naming scheme. The joke is that if a hard refresh resets the browser display and cache, a harder refresh should reset the source of the data by cycling power in the data center. Assuming no damage was done, this would reset the memory on the server, erasing any information that had not been written to disk, and setting the server to the state it was in at launch. This would cause considerable downtime, and would be unlikely to help the user at all.
The harder refresh uses six keys, including the non-standard 'HYPER' key, a feature of the Space cadet keyboard.
The fifth option, hardest refresh, moves beyond resetting the source of the data and resets the entire internet back to ARPANET, an early military network which was a forerunner to the modern internet. The implications of this are not made clear, but it should be noted that it wouldn't help to fix any problems a user is experiencing in-browser, as HTTP, the protocol by which web pages are sent, was not developed until late 1990, the year ARPANET was decommissioned.
The hardest refresh shortcut uses fifteen keys, including non-standard ones such as Ø and ⏏. (The latter is the "eject" key found on [older?] Mac keyboards.) The shortcut makes amusing comparisons about a shortcut that includes not only the F5 function key, but also the keys for the letter "F" and the digit "5", as well as the similarity in appearance between O, 0, and Ø.
The title text suggests that the inclusion of both the Windows key and Command key in the hardest refresh shortcut is a security measure akin to the Two-man rule, as it would require two keyboards to enter.
|| This transcript is incomplete. Please help editing it! Thanks.
| Refresh Type
|| Example Shortcuts
| Soft Refresh
|| Gmail REFRESH Button
| Normal Refresh
|| F5, CTRL-R, ⌘R
|| CTRL-F5, CTRL-⇧, ⌘⇧R
|| Refreshes page including cached files
|| Remotely cycles power to datacenter
|| CTRL-⌘⊞⇧#-R-F5-F-5-ESC-O-0-Ø-⏏-SCROLL LOCK
|| Internet starts over from ARPANET
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