An error message is information displayed when an unforeseen problem occurs, usually on a computer or other device. On modern operating systems with graphical user interfaces, error messages are often displayed using dialog boxes. Error messages are used when user intervention is required, to indicate that a desired operation has failed, or to relay important warnings (such as warning a computer user that they are almost out of hard disk space). Error messages are seen widely throughout computing, and are part of every

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

or computer hardware device. Proper design of error messages is an important topic in usability and other fields of

human–computer interaction Human–computer interaction (HCI) is research in the design and the use of computer technology, which focuses on the interfaces between people ( users) and computers. HCI researchers observe the ways humans interact with computers and design ...

Common error messages

The following error messages are commonly seen by modern computer users: ;Access denied :This error occurs if the user doesn't have privileges to a file, or if it has been

locked Lock(s) may refer to: Common meanings *Lock and key, a mechanical device used to secure items of importance *Lock (water navigation), a device for boats to transit between different levels of water, as in a canal Arts and entertainment * ''Lock ...

by some program or user. ;Device not ready :This error most often occurs when there is no

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined ...

(or a bad disk) in the disk drive and the system tries to perform tasks involving this disk. ;File not found :The file concerned may have been damaged, moved, deleted, or a bug may have caused the error. Alternatively, the file simply might not exist, or the user has mistyped its name. This is most commonly seen on the internet with outdated links to web pages that no longer exist. On a local computer, this is more frequent on command line interfaces than on graphical user interfaces where files are presented iconically and users do not type file names. ;Low Disk Space :This error occurs when the hard drive is (nearly) full. To fix this, the user should close some programs (to free swap file usage) and delete some files (normally temporary files, or other files after they have been backed up), or get a bigger hard drive. ;Out of memory :This error occurs when the system has run out of memory or tries to load a file too large to store in RAM. The fix is to close some programs or install more memory. ; rogram namehas stopped working. :This message and similar ones are displayed by several operating systems when program causes a general protection fault or invalid page fault.

Notable error messages

* Abort, Retry, Fail? - A notoriously confusing error message seen in

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...

* Bad command or file name - Another notoriously common and confusing error message seen in

* The Blue Screen of Death - On Microsoft Windows and ReactOS operating systems, this screen appears when Windows or ReactOS can no longer run because of a severe error. It is roughly analogous to a kernel panic on

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which i ...

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

, or

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac (computer), Mac computers. Within the market of ...

. * Can't extend - an error message from

Acorn The acorn, or oaknut, is the nut of the oaks and their close relatives (genera '' Quercus'' and ''Lithocarpus'', in the family Fagaceae). It usually contains one seed (occasionally two seeds), enclosed in a tough, leathery shell, and bo ...

DFS DFS may refer to: Brands and enterprises * Dancer Fitzgerald Sample, advertising agency, now Saatchi & Saatchi * DFS Furniture, a furniture retailer in the United Kingdom and Ireland * DFS Group (Duty Free Shoppers), Hong Kong * DFS Program Excha ...

. DFS stores files in non-fragmented contiguous disk space, this error is caused when trying to extend an open random-access file into space that is already occupied by another file. * Guru Meditation - an error message from the Commodore Amiga, roughly analogous to a kernel panic or BSOD, also adopted by more recent products such as VirtualBox. * HTTP 404 - A file not found error seen on the

World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web se ...

, usually resulting from a link to a page that has been moved or deleted, or a mistyped URL * lp0 on fire - A Unix warning that the printer may be "on fire", literally or not * Not a typewriter - A Unix error message that is confusing due to its now obsolete use of the word "

typewriter A typewriter is a mechanical or electromechanical machine for typing characters. Typically, a typewriter has an array of keys, and each one causes a different single character to be produced on paper by striking an inked ribbon selective ...

", and which is sometimes output when the nature of the error is seemingly entirely different * PC LOAD LETTER - An error on several HP laser printers that simply asked the user to add "Letter" size paper in a confusing way * SYNTAX ERROR - Seen on many computer systems when the received instructions are in a format they don't understand * HTTP 504 - An error found on the

stating that a gateway timeout occurred in the internet link. * Error 1603 - An error that states that a problem during installation of a

computer program A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components. A computer progra ...

, this error particularly occurs on

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...

computer systems. * <application name> has stopped - An error message commonly found on

Android Android may refer to: Science and technology * Android (robot), a humanoid robot or synthetic organism designed to imitate a human * Android (operating system), Google's mobile operating system ** Bugdroid, a Google mascot sometimes referred to ...

devices, which states a current running application unexpectedly stops working or crashes. * Success - one of the error messages (in this instance, POSIX) that occurs when the program has detected an error condition, yet the actual error message printing routine relies on C library to print the error reported by the operating system (in this case, errno.h), while the underlying

system call In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, acc ...

s have succeeded and report no errors (in this case,

errno 
 0

). This is a form of sloppy error handling that is particularly confusing for the user. * onnection Time Out Error Mac- Error occurs on Mac systems when it takes more time to connect wireless networks.

Fail pets

With the rise of Web 2.0 services such as

Twitter Twitter is an online social media and social networking service owned and operated by American company Twitter, Inc., on which users post and interact with 280-character-long messages known as "tweets". Registered users can post, like, and ...

, end-user facing error messages such as HTTP 404 and

HTTP 500 This is a list of Hypertext Transfer Protocol (HTTP) response status codes. Status codes are issued by a server in response to a client's request made to the server. It includes codes from IETF Request for Comments (RFCs), other specifications, ...

started to be displayed with whimsical characters, termed Fail Pets or Error Mascots. The term "Fail Pet" was coined, or at least first used in print, by Mozilla Engineer Fred Wenzel in a post on his blog entitled "Why Wikipedia might need a fail-pet — and why Mozilla does not." Dr. Sean Rintel argues that error messages are a critical strategic moment in

brand awareness Brand awareness is the extent to which customers are able to recall or recognize a brand under different conditions. Brand awareness is one of two dimensions from brand knowledge, an associative network memory model. Brand awareness is a key consi ...

and loyalty. Fail pets are of interest to marketers because they can result in brand recognition (especially through earned media). "However, that same recognition carries the danger of highlighting service failure." The most famous fail pet is Twitter's Fail Whale (see

service outages). Other fail pets include: * Ars Technica: Moon Shark (March 3, 2013) * FarmVille on Facebook: Sad cow. *

GitHub GitHub, Inc. () is an Internet hosting service for software development and version control using Git. It provides the distributed version control of Git plus access control, bug tracking, software feature requests, task management, co ...

: Octocat *

Google Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...

: Broken robot (March 2, 2011) *

iCloud iCloud is a Personal cloud, cloud service from Apple Inc. launched on October 12, 2011 as a successor to MobileMe. , the service had an estimated 850 million users, up from 782 million users in 2016. iCloud enables users to sync their data to t ...

: Cloud with Apple System 7 emoticon-style face and a magnifying glass * Macintosh:

Sad Mac The classic Macintosh startup sequence includes hardware tests which may trigger the startup chime, Happy Mac, Sad Mac, and Chimes of Death. On Macs running macOS Big Sur or later the startup sound is enabled by default, but can be disabled by ...

Palliser Furniture Palliser Furniture is a family-owned furniture manufacturing company headquartered in Winnipeg, Manitoba, Canada. , the company was the largest manufacturer of made-to-order leather furniture in North America.Tumblr: Tumbeasts (January 25, 2011) *

: Fail Whale / Twitter Robot (July 30, 2008) *

YouTube YouTube is a global online video sharing and social media platform headquartered in San Bruno, California. It was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim. It is owned by Google, and is the second most ...

: Televisions (on main site), light static inside video window (embedded video) * Cartoon Network: BMO sia Domo * Google Chrome: T-Rex * Patreon: Red fox with a helmet floating in

space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually con ...

* VK: Sad Vkontakte dog * Scratch
Giga
scratching his head

Message format

The form that error messages take varies between operating systems and programs. Error messages on hardware devices, like computer peripherals, may take the form of dedicated lights indicating an error condition, a brief code that needs to be interpreted using a look-up sheet or a manual, or via a more detailed message on a display. On computers, error messages may take the form of text printed to a console, or they may be presented as part of a graphical user interface. Error messages are often presented as a

dialog box The dialog box (also called dialogue box (non-U.S. English), message box or simply dialog) is a graphical control element in the form of a small window that communicates information to the user and prompts them for a response. Dialog boxes ar ...

, which makes them cause a following mode error in the user interaction. In many cases the original error can be avoided by error prevention techniques. Instead of raising an error message the system design should have avoided the conditions that caused the error. While various graphical user interfaces have different conventions for displaying error messages, several techniques have become common: * A dialog box, or pop-up message, appears in a window on the screen, blocking further interaction with the computer until it is acknowledged. On Mac OS X, sheets are a form of dialog box that are attached to a specific window. * Notification icons appear to notify a user about a condition without interrupting their work. On Windows, notification icons appear in the System Tray. On Mac OS X, notification icons may appear in the menu bar, or may take the form of an application's icon "bouncing" in the Dock. The GNOME user interface for Unix systems can display notification icons in a panel. * Minor errors may be displayed in a status bar, a small portion of an application's window that can display brief messages to the user. The three main factors that influence the design of error messages are technical limitations, the amount of information to be presented, and what kind of user input is required. Some systems have technical limitations that may constrain the amount of information an error message can contain. For example, a printer with a sixteen-character alphanumeric display can only show a very limited amount of information at once, so it may need to display very terse error messages. Even with computer monitors, the programmer must consider the smallest monitor that a user might reasonably use, and ensure that any error messages will fit on that screen. The nature of the error determines the amount of information required to effectively convey the error message. A complex issue may require a more detailed error message in order to adequately inform the user of the problem.

Security

When designing error messages, software designers should take care to avoid creating security vulnerabilities. The designer should give the user enough information to make an intelligent decision, but not so much information that the user is overwhelmed or confused. Extraneous information may be hidden by default or placed in a separate location. Error message should not expose information that can be exploited by a

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to obtain information that is otherwise difficult to obtain. Examples are systems which may show either "invalid user" or "invalid password" depending on which is incorrect, and the error page in the web server IIS 5.0 which provides a complete technical description of the error including a source code fragment.

References

External links

A more useful 404 (A List Apart)Avoid being embarrassed by your error messages (UX Matters)
{{DEFAULTSORT:Error Message Computer errors Human–computer interaction