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Revision as of 12:19, 18 December 2013

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Refresh Types
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.
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.

Explanation

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.

Soft refresh

Soft refresh refers to an operation in a web page that requests new information without reloading the entire page. The given example, Gmail, includes a feature that allows users to poll new emails and show it in the inbox interface. It is a command using JavaScript and Ajax to load new contents from the server in the background and only update necessary components of the page. Since modern web applications do this also automatically in short time intervals those buttons are mostly unnecessary. In Gmail a user will see a new message instantly.

Normal refresh

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. If the page has been opened before a new comic release, pressing F5 afterwards causes reload and the new comic is shown.

Hard refresh

What Randall calls hard refresh is a less common browser operation forcing the browser to re-download every part of the webpage, ignoring any cached content. Caching is a common way of decreasing webpage load times. Browsers save resources such as images or CSS stylesheets on the first visit on a webpage and use the local copy on subsequent visits. It allows them to decrease amount of transfer needed to show the webpage, but prevents showing changes made to the resources (for example a web developer changing the stylesheet). In those cases the hard refresh ensures that each part of the website is downloaded in its newest form.

If there is a Web-Proxy or a Cloud-Cache (like used for this wiki) in between the browser and the Web-Server this type of refreshing may not work. In this case, unless a purge link is available, 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 behaviour by including special meta-tags in the HTML header to suppress caching, but not all proxies or clouds follow these instructions.

Harder refresh

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.

In orchestrated environment it may indirectly cause some virtual machines in the cloud to be rebooted and assigned to an other web server needing more workload. But a growing workload is caused by hundreds or thousands additional requests and not just a single key combination from one browser. And rebooting an actual physical server upon a web page request is not possible, unless there is a software or operating system bug that will cause exactly this.

The harder refresh uses six keys, including the non-standard 'HYPER' key, a feature of the Space cadet keyboard.

Hardest refresh

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 former is a key found on Norwegian and Danish keyboards, the latter is the "eject" key found on Mac keyboards and some laptops.) 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.

Transcript

Ambox notice.png This transcript is incomplete. Please help editing it! Thanks.
[A table with three columns is shown. The header is:]
Refresh Type; Example Shortcuts; Effect
[First row:]
Soft Refresh
[The word refresh has a border to mimic a button:]
Gmail REFRESH Button
Requests update within JavaScript
[Second row:]
Normal Refresh
[Two PC shortcuts and the Apple command key followed by an R:]
F5, CTRL-R, ⌘R
Refreshes page
[Third row:]
Hard Refresh
[One PC shortcut, the combination Control plus Shift, and the Apple command key followed by Shift and R:]
CTRL-F5, CTRL-⇧, ⌘⇧R
Refreshes page including cached files
[Fourth row:]
Harder Refresh
[One single combination using Control plus Shift plus Hyper plus Escape plus R plus F5:]
CTRL-⇧-HYPER-ESC-R-F5
Remotely cycles power to datacenter
[Fifth row:]
Hardest Refresh
[One single combination using Control plus the Apple command key plus the Windows key plus Shift plus the hash key plus R plus F5 plus F plus 5 plus Escape plus the letter O plus a slashed zero with a small slash plus a slashed zero with a long slash plus an eject sign plus Scroll Lock:]
CTRL-⌘⇧#-R-F5-F-5-ESC-O-0-Ø-⏏-SCROLL LOCK
Internet starts over from ARPANET


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