Acid2 is a webpage that test

web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used o ...

s' functionality in displaying aspects of

HTML The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaSc ...

markup, CSS 2.1 styling, PNG images, and

data URI The data URI scheme is a uniform resource identifier (URI) scheme that provides a way to include data in-line in Web pages as if they were external resources. It is a form of file literal or here document. This technique allows normally separat ...

s. The test page was released on 13 April 2005 by the Web Standards Project. The Acid2 test page will be displayed correctly in any application that follows the

World Wide Web Consortium The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 and led by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working ...

and

Internet Engineering Task Force The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...

specifications for these technologies. These specifications are known as

web standards Web standards are the formal, non-proprietary standards and other technical specifications that define and describe aspects of the World Wide Web. In recent years, the term has been more frequently associated with the trend of endorsing a set of s ...

because they describe how technologies used on the web are expected to function. The Acid2 tests rendering flaws in

s and other applications that render HTML. Named after the acid test for gold, it was developed in the spirit of

Acid1 Acid1, originally called the Box Acid Test, was a test page for web browsers. It was developed in October 1998 and was important in establishing baseline interoperability between early web browsers, especially for the Cascading Style Sheets 1.0 ...

, a relatively narrow test of compliance with the Cascading Style Sheets 1.0 (CSS1)

standard Standard may refer to: Symbols * Colours, standards and guidons, kinds of military signs * Standard (emblem), a type of a large symbol or emblem used for identification Norms, conventions or requirements * Standard (metrology), an object th ...

. As with Acid1, an application passes the test if the way it displays the test page matches a reference image. Acid2 was designed with

Microsoft Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated IE or MSIE) is a series of graphical web browsers developed by Microsoft which was used in the Windows line of operating systems (in W ...

particularly in mind. The creators of Acid2 were dismayed that Internet Explorer did not follow web standards. It was prone to display web pages differently from other browsers, causing web developers to spend time

tweaking Tweaking refers to fine-tuning or adjusting a complex system, usually an electronic device. Tweaks are any small modifications intended to improve a system. In electronics, it is a synonym for "trimming." Analog circuit boards often have small po ...

their web pages. Acid2 challenged Microsoft to make Internet Explorer comply with web standards. On 31 October 2005, Safari 2.0.2 became the first browser to pass Acid2.

Opera Opera is a form of theatre in which music is a fundamental component and dramatic roles are taken by singers. Such a "work" (the literal translation of the Italian word "opera") is typically a collaboration between a composer and a libr ...

Konqueror Konqueror is a free and open-source web browser and file manager that provides web access and file-viewer functionality for file systems (such as local files, files on a remote FTP server and files in a disk image). It forms a core part of t ...

Firefox Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements current ...

, and others followed. With the release of

Internet Explorer 8 Windows Internet Explorer 8 (IE8) is a web browser for Windows. It was released by Microsoft on March 19, 2009, as the eighth version of Internet Explorer and the successor to Internet Explorer 7. It was the default browser in Windows 7 (later def ...

on 19 March 2009, the latest versions of all major desktop web browsers now pass the test until IE10 was released, which fails the test. Its successor,

Microsoft Edge Microsoft Edge is a proprietary, cross-platform web browser created by Microsoft. It was first released in 2015 as part of Windows 10 and Xbox One and later ported to other platforms as a fork of Google's Chromium open-source project: Android ...

, is able to render it correctly as of Windows 10 version 1607. Acid2 was followed by

Acid3 The Acid3 test is a web test page from the Web Standards Project that checks a web browser's compliance with elements of various web standards, particularly the Document Object Model (DOM) and JavaScript. If the test is successful, the results ...

. The test fails when browsers become compliant with current CSS collapse and margin standards.

History

Acid2 was first proposed by

Håkon Wium Lie Håkon Wium Lie (born July 26, 1965) is a Norwegian web pioneer, a standards activist, and the Chief Technology Officer of Opera Software from 1998 until the browser was sold to new owners in 2016. He is best known for developing Cascading Sty ...

, chief technical officer of

Opera Software Opera is a Norwegian multinational technology company and subsidiary of Kunlun that specializes in web browser development, fintech, as well as services such as Opera News and YoYo Games. The company's total user base, including users of its ...

and creator of the widely used Cascading Style Sheets

web standard Web standards are the formal, non-proprietary standards and other technical specifications that define and describe aspects of the World Wide Web. In recent years, the term has been more frequently associated with the trend of endorsing a set of s ...

. In a 16 March 2005 article on CNET, Lie expressed dismay that

did not properly support web standards and hence was not completely interoperable with other browsers. He announced that Acid2 would be a challenge to

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washin ...

to design

Internet Explorer 7 Windows Internet Explorer 7 (IE7) (codenamed Rincon) is a web browser for Windows. It was released by Microsoft on October 18, 2006, as the seventh version of Internet Explorer and the successor to Internet Explorer 6. Internet Explorer 7 is pa ...

, then in development, to achieve a greater degree of standards compliance than previous versions of Internet Explorer. The original

test had forced browser makers to fix their applications or face embarrassment; Lie hoped that Acid2 would do the same. Lie and a colleague, Ian Hickson, created the first draft of the test in February 2005. Ian Hickson coded the final test in collaboration with the Web Standards Project and the larger web community. It was officially released on 13 April 2005 and at that time, every web browser failed it spectacularly. On 23 April 2005, Acid2 was updated to fix a bug that made the mouth appear too close to the nose. After several complaints, the test was again updated in January 2006 to remove a test for unpopular SGML-style comments that were never widely implemented. In browsers that do not implement SGML-style comments, the original test displayed the word "ERROR" on the bottom part of the face. In March 2008, Ian Hickson released

as a follow-up to Acid2. While Acid2 primarily tests CSS, Acid3 focuses more on

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...

and other "

Web 2.0 Web 2.0 (also known as participative (or participatory) web and social web) refers to websites that emphasize user-generated content, ease of use, participatory culture and interoperability (i.e., compatibility with other products, systems, and ...

" technologies.

Microsoft's response

In July 2005, Chris Wilson, the Internet Explorer Platform Architect, stated that passing Acid2 was not a priority for

, describing the test as a "wish list" of features rather than a true test of standards compliance. In December 2007, Microsoft announced that all the changes required to pass Acid2 would be made available in

, but that the changes would not be turned on by default, meaning that IE8 would not actually pass the test. The concern was that switching to a new behavior would cause too many problems in web pages expecting Internet Explorer's old, non-compliant behavior. Then in March 2008 Microsoft released IE8 beta 1 and turned on the changes by default after all. James Pratt, product manager for IE8, explained that this decision was made so that "developers can spend more time building features and cool stuff, and less time just trying to tweak their sites across different browsers." Another unresolved standards compliance issue caused IE8 beta 1 to fail if not all elements of the test were hosted from the same server. In August 2008 Microsoft released IE8 beta 2, which resolved the issue. As of that beta, however, standards mode is not turned on by default for pages loaded in the " Intranet Zone". This zone is active for pages loaded via

UNC path A path is a string of characters used to uniquely identify a location in a directory structure. It is composed by following the directory tree hierarchy in which components, separated by a delimiting character, represent each directory. The del ...

s, named addresses without dots (like http://mysite/), and sites that bypass the

proxy Proxy may refer to: * Proxy or agent (law), a substitute authorized to act for another entity or a document which authorizes the agent so to act * Proxy (climate), a measured variable used to infer the value of a variable of interest in climate ...

settings. As such, IE8 will not pass the Acid2 test if loaded in these cases.

Overview of standards tested

Acid2 tests a variety of

published by the

and the

. With the exception of CSS 2.1, all web standards tested were codified before the year 2000. CSS 2.1 was a candidate recommendation at the time of Acid2's release, and was still a candidate recommendation as of 23 April 2009. Specifically, Acid2 tests these functions on your browser;

Alpha transparency In computer graphics, alpha compositing or alpha blending is the process of combining one image with a background to create the appearance of partial or full transparency. It is often useful to render picture elements (pixels) in separate pas ...

in PNG-format images, which is seen when the eyes of the smiley face use ''alpha transparency'', which is part of the 1996 Portable Network Graphics specification. Alpha transparency blends the eyebrows into the face smoothly and elegantly. This was a significant issue because

Internet Explorer 6 Microsoft Internet Explorer 6 (IE6) is a graphical web browser developed by Microsoft for Windows operating systems. Released on August 24, 2001, it is the sixth, and by now discontinued, version of Internet Explorer and the successor to Internet ...

, the most widely used web browser at the time Acid2 was released, did not support alpha transparency. This deficiency was rectified in

, bringing Internet Explorer in line with other web browsers in this regard. object element which, once again, the eyes also test support of the HTML object element. The object element has been a part of HTML since HTML 4 was released in 1998, yet by 2005 it still was not completely supported in all web browsers. The creators of Acid2 considered object element support important because it allows for content fallback—if an object fails to load, then the browser can display alternative (generally simpler, more reliable) content in its place.

Data URI The data URI scheme is a uniform resource identifier (URI) scheme that provides a way to include data in-line in Web pages as if they were external resources. It is a form of file literal or here document. This technique allows normally separat ...

s, where the actual images that form the eyes are encoded as data URIs, which allow multimedia to be embedded in web pages rather than stored as a separate file. Acid2 tests the most common case, where a

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that ta ...

image is

base64 In computer programming, Base64 is a group of binary-to-text encoding schemes that represent binary data (more specifically, a sequence of 8-bit bytes) in sequences of 24 bits that can be represented by four 6-bit Base64 digits. Common to all bina ...

-encoded into text and then that encoded text is included in a data URI in the web page. Although the IETF published the data URI specification in 1998, they never formally adopted it as a standard. Nonetheless, the HTML 4.01 specification references the data URI scheme, and data URI support has now been implemented in most browsers.'Absolute, relative, and fixed CSS positioning, which mean the web developer specifies the exact X and Y coordinates where an element is to be placed into the page, the web developer specifies an X and Y offset from the usual position of the element, and the element is placed relative to the browser window, and scrolls with the window rather than with the rest of the page. The CSS box model, which is a feature that allows the web designer to specify dimensions, padding, borders, and margins, and was the focus of the original

test. Acid2 not only retests margin support but also tests minimum and maximum heights and widths, features new to CSS 2.0. CSS table formatting, which allows the web designer to apply table formatting without traditional HTML table markup on the CSS. CSS generated content, Using CSS generated content, web developers can add decorations and annotations to specified elements without having to add the content to each one individually. CSS parsing, in which a number of illegal CSS statements are present in Acid2 to test error handling. Standards-compliant browsers are expected to handle these errors as the CSS specification directs. This helps ensure cross-browser compatibility by making all browsers treat CSS with the same level of strictness, so that what works in one browser should not cause errors in another. Paint order, which means that Acid2 requires that the browser has standard paint order. That is, overlapping elements should be placed or ''painted'' on top of each other in the correct order, and finally Hovering effects, which is When the user moves his or her mouse over the smiley face's nose, it turns blue. This is called a hovering effect, and while it has traditionally been used for hyperlinks, it should work on a wide variety of HTML elements. Because Acid2 is not a comprehensive test, it does not guarantee total conformance to any particular standard. A variant of the Acid2 test that does not test for data URI support is also available from the Web Standards Project.

Passing conditions

A passing score is only considered valid if the browser's default settings were used. Actions such as changing font sizes, zoom level, and applying user stylesheets can break the display of the test. This is expected and is not relevant to a browser's compliance. These browser settings and user actions invalidate the test, which are: Scrolling, Resizing the browser window, Zooming in or out, Disabling images, Using

's ''Fit to width'' or ''Small Screen Rendering'' modes, Applying custom fonts, colors, styles, etc., User JavaScript or

Greasemonkey Greasemonkey is a userscript manager made available as a Mozilla Firefox extension. It enables users to install scripts that make on-the-fly changes to web page content after or before the page is loaded in the browser (also known as augmen ...

scripts, Enabling

Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated IE or MSIE) is a series of graphical web browsers developed by Microsoft which was used in the Windows line of operating systems ( ...

's "compatibility view"

Compliant applications

Usage share of web browsers that pass Acid2

If rendered correctly, Acid2 will appear as a

smiley A smiley, sometimes referred to as a smiley face, is a basic ideogram that represents a smiling face. Since the 1950s it has become part of popular culture worldwide, used either as a standalone ideogram, or as a form of communication, such a ...

face below the text " Hello World!" in the user's browser, with the nose turning blue when the mouse cursor hovers over it. At the time of the test's release, every browser failed it, but now a number of browsers pass it. Many browsers as of today manage to pass the test, which includes: the desktop version of

, which passes the test as of Windows 10 build 14393.105;

, the web browser that comes with

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 ser ...

;

Odyssey Web Browser Origyn Web Browser (OWB) is a discontinued web browser that was synchronized with WebKit and sponsored by the technology company Pleyo. OWB provides a meta-port to an abstract platform with the aim of making porting to embedded or lightweight s ...

, a web browser for

AmigaOS AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early versions ...

and

MorphOS MorphOS is an AmigaOS-like computer operating system (OS). It is a mixed proprietary and open source OS produced for the Pegasos PowerPC (PPC) processor based computer, PowerUP accelerator equipped Amiga computers, and a series of Freescale dev ...

; Gecko-based browser, Mozilla Firefox, a web browser for Windows, Mac OS, and

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, w ...

;

SeaMonkey SeaMonkey is a free and open-source Internet suite. It is the continuation of the former Mozilla Application Suite, based on the same source code, which itself grew out of Netscape Communicator and formed the base of Netscape 6 and Netscape ...

, an

Internet suite An Internet suite is an Internet-related software suite. Internet suites usually include a web browser, e-mail client (often with a news client and address book), download manager, HTML editor, and an IRC client. The diversity of Internet suite o ...

for Windows, Mac OS, and Linux;

Songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5000 ...

, a media player and web browser for Windows, Mac OS, and Linux; Camino, a web browser for Mac OS;

Mozilla Thunderbird Mozilla Thunderbird is a free and open-source cross-platform email client, personal information manager, news client, RSS and chat client developed by the Mozilla Foundation and operated by subsidiary MZLA Technologies Corporation. The projec ...

, an email client for Windows, Mac OS, and Linux;

Firefox for mobile Firefox for Android is a web browser developed by Mozilla for Android smartphones and tablet computers. As with its desktop version, it uses the Gecko layout engine, and supports features such as synchronization with Firefox Sync, blocking web ...

, a web browser for mobile devices; Miro, an RSS aggregator; BitTorrent client, web browser and media player; Mozilla Sunbird, a calendar application for Windows, Mac OS, and Linux; Spicebird 0.8, a personal information manager for Windows, Mac OS, and Linux; WebRunner (formerly Prism), a web application platform for Windows, Mac OS, and Linux;

WebKit WebKit is a browser engine developed by Apple and primarily used in its Safari web browser, as well as on the iOS and iPadOS version of any web browser. WebKit is also used by the BlackBerry Browser, PlayStation consoles beginning from the P ...

- and

KHTML KHTML is a browser engine developed by the KDE project. It is the default engine of the Konqueror browser, but it has not been actively worked on since 2016. Moreover, KHTML will be discontinued for KDE Frameworks 6. Built on the KParts fra ...

-based browsers: Safari, the web browser included in Mac OS; Google Chrome, a web browser for Windows, Mac OS, and Linux;

, a web browser for Linux;

OmniWeb OmniWeb is a discontinued web browser that was developed and marketed by The Omni Group exclusively for Apple's macOS operating system. Though a stable version is no longer maintained, it is still available as a free download and unstable version ...

, a web browser for Mac OS;

Shiira Shiira (シイラ, Japanese for the common dolphin-fish) is a discontinued open source web browser for the Mac OS X operating system. According to its lead developer Makoto Kinoshita, the goal of Shiira was "to create a browser that is better a ...

, a web browser for Mac OS;

iCab iCab is a web browser for Mac OS by Alexander Clauss, derived from Crystal Atari Browser (CAB) for Atari TOS compatible computers. It was one of the few browsers still updated for the classic Mac OS prior to that version being discontinued afte ...

, a web browser for Mac OS; Web, the official GNOME web browser;

Midori Midori (みどり, ミドリ, , , ) is the Japanese word for "green" and may refer to: Places * Midori, Gunma * Midori-ku, Chiba * Midori-ku, Nagoya * Midori-ku, Sagamihara * Midori-ku, Saitama * Midori-ku, Yokohama People Given name * M ...

, the official Xfce web browser; The Google Earth integrated web browser; Presto-based browsers:

, a web browser for Windows, Mac OS, Linux, BSD and Solaris with mobile versions for all mobile phones, tablets and all

Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...

products like

iPad The iPad is a brand of iOS and iPadOS-based tablet computers that are developed by Apple Inc. The iPad was conceived before the related iPhone but the iPhone was developed and released first. Speculation about the development, operating ...

;

Internet Channel The Wii Menu is the graphical shell of the Wii and Wii U game console, as part of the Wii system software. It has four pages, each with a 4:3 grid, and each displaying the current time and date. Available applications, known as "channels", are ...

, a version of the Opera browser for the Nintendo Wii game console; and

Prince A prince is a male ruler (ranked below a king, grand prince, and grand duke) or a male member of a monarch's or former monarch's family. ''Prince'' is also a title of nobility (often highest), often hereditary, in some European states. T ...

, an XML-to-PDF converter for Windows, Mac OS, and Linux. However, even though

Opera Mini Opera Mini is a mobile web browser made by Opera. It was primarily designed for the Java ME platform, as a low-end sibling for Opera Mobile, but it is now developed exclusively for Android. It was previously developed for iOS, Windows 10 Mobil ...

is based on the same rendering engine as

for

personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...

s, it does not pass the Acid2 test. This is because Opera Mini intentionally reformats web pages to try to make them more suitable for devices with small screens.

Timeline of passing applications

The following is a list of releases noting significant releases of applications that passed the test. New applications that have passed Acid2 since their first official release are not included in the timeline.

References

External links

{{Spoken Wikipedia, Acid2.ogg, date=2009-04-13
Acid2 test

Acid2 test information

Acid2 in major browsers

Web Standards Project collection of Acid tests

Web Standards Project press release 13 Apr 2005

Acid2 timeline
Acid tests Web software 2005 introductions Test items de:Acid (Browsertests)#Acid2 sv:Acid webbläsartester#Acid2