Google Chrome

Google Chrome

Google Chrome is a web browser developed by Google and based on the WebKit layout engine and application framework. In February 2009, it had a share of 1.15% of the web browser market. It was first released as a beta version for Microsoft Windows on September 2, 2008, and the public stable release was on December 11, 2008. The name is derived from the graphical user interface frame, or "chrome", of web browsers.

Chromium is the open source project behind Google Chrome. The Google-authored portion of it is released under the BSD license, with other parts being subject to a variety of different permissive open-source licenses, including the MIT License, the LGPL, the Ms-PL and a MPL/GPL/LGPL tri-license. It implements the same feature set as Chrome, but has a slightly different logo.

The release announcement was originally scheduled for September 3, 2008, and a comic by Scott McCloud was to be sent to journalists and bloggers explaining the features of and motivations for the new browser. Copies intended for Europe were shipped early and German blogger Philipp Lenssen of Google Blogoscoped made a scanned copy of the 38-page comic available on his website after receiving it on September 1, 2008. Google subsequently made the comic available on Google Books and their site and mentioned it on its official blog along with an explanation for the early release.

The browser was first publicly released for Microsoft Windows (XP and later only) on September 2, 2008 in 43 languages, officially a beta version. Chrome quickly gained about 1% market share. Mac OS X and Linux versions are under development. In the end of 2008, a message saying that a "test shell" is available to build on Linux was placed in the Chromium project's developer wiki. Some have tried this shell, which apparently lacked many features, but appeared to function quite well in rendering web sites (including JavaScript). In March 2009, the test shell was replaced by a pre-alpha version of the Chromium browser, which looks similar to the Windows release, but is still very far from complete.

On September 2, a CNET news item drew attention to a passage in the terms of service for the initial beta release, which seemed to grant to Google a license to all content transferred via the Chrome browser. The passage in question was inherited from the general Google terms of service. On the same day, Google responded to this criticism by stating that the language used was borrowed from other products, and removed the passage in question from the Terms of Service. Google noted that this change would "apply retroactively to all users who have downloaded Google Chrome." There were subsequent concern and confusion about whether and what information the program communicates back to Google. The company stated that usage metrics are only sent when users opt in by checking the option "help make Google Chrome better by automatically sending usage statistics and crash reports to Google" when the browser is installed.

The first release of Google Chrome passed the Acid1 and Acid2 (not fully, a small artifact appears) tests. It also passed 79 out of the 100 subtests of the Acid3, higher than both Internet Explorer 7, which scored 14, and Firefox 3, which scored 71, but lower than Opera, which scored 83. When compared with development builds of Firefox, Internet Explorer, Opera, and Safari, Chrome scored lower than Firefox 3.1 Beta 1 (85), Opera (100), and Safari 4 (Developer Preview) (100), but still higher than Internet Explorer (21). However, the current Dev channel build scores 100 out of 100 while still failing the link test.

On January 9, 2009, CNET reports that Google plans to release versions for Mac OS X and Linux by the first half of the year.

Primary design goals were improvements in security, speed, and stability compared to existing browsers. There also were extensive changes in the user interface. Chrome was assembled from 26 different code libraries from Google and others from third parties such as Netscape.

Chrome periodically downloads updates of two blacklists (one for phishing and one for malware), and warns users when they attempt to visit a harmful site. This service is also made available for use by others via a free public API called "Google Safe Browsing API". Google notifies the owners of listed sites who may not be aware of the presence of the harmful software.

Chrome will typically allocate each tab to fit into its own process to "prevent malware from installing itself" or "using what happens in one tab to affect what happens in another", however the actual process allocation model is more complex. Following the principle of least privilege, each process is stripped of its rights and can compute, but can not write files or read from sensitive areas (e.g. documents, desktop)—this is similar to the "Protected Mode" that is used by Internet Explorer 7 on Windows Vista. The Sandbox Team is said to have "taken this existing process boundary and made it into a jail"; for example, malicious software running in one tab is unable to sniff credit card numbers, interact with the mouse, or tell Windows to "run an executable on start-up" and it will be terminated when the tab is closed. This enforces a simple computer security model whereby there are two levels of multilevel security (user and sandbox) and the sandbox can only respond to communication requests initiated by the user.

Typically, plugins such as Adobe Flash Player are not standardized and as such, cannot be sandboxed as tabs can be. These often need to run at, or above, the security level of the browser itself. To reduce exposure to attack, plugins are run in separate processes that communicate with the renderer, itself operating at "very low privileges" in dedicated per-tab processes. Plugins will need to be modified to operate within this software architecture while following the principle of least privilege. Chrome supports the Netscape Plugin Application Programming Interface (NPAPI), but does not support the embedding of ActiveX controls. Also, Chrome does not have an extension system such as Mozilla's XPInstall architecture. Java applets support is available in Chrome as part of Java 6 update 11.

A private browsing feature called Incognito mode is provided that prevents the browser from storing any history information or cookies from the websites visited. This feature has been referred to as a porn mode similar to the private browsing feature available in Apple's Safari and Internet Explorer 8.

A denial-of-service vulnerability was found that allowed a malicious web page to crash the whole web browser. However, Google Chrome developers confirmed the flaw, and it was fixed in the 0.2.149.29 release.

The JavaScript virtual machine was considered a sufficiently important project to be split off (as was Adobe/Mozilla's Tamarin) and handled by a separate team in Denmark. According to Google, existing implementations were designed "for small programs, where the performance and interactivity of the system weren't that important," but web applications such as Gmail "are using the web browser to the fullest when it comes to DOM manipulations and Javascript." The resulting V8 JavaScript engine has features such as hidden class transitions, dynamic code generation, and precise garbage collection. Tests by Google on 9/2/2008 showed that V8 was about twice as fast as Firefox 3.0 and the WebKit nightlies (of which Safari is a lightly modified version) . Ten days later, SquirrelFish Extreme was announced by the WebKit, making the performance difference between WebKit and Chromium a dead heat again.

Several websites performed benchmark tests using the SunSpider JavaScript Benchmark tool as well as Google's own set of computationally intense benchmarks, which includes ray tracing and constraint solving. They unanimously reported that Chrome performed much faster than all competitors against which it had been tested, including Safari, Firefox 3.0, Internet Explorer 7, and Internet Explorer 8. While Opera had not been compared to Chrome in those comparisons, in previous tests, it had been shown to be slightly slower than Firefox 3.0, which in turn, was slower than Chrome. Another blog post by Mozilla developer Brendan Eich compared Chrome's V8 engine to his own TraceMonkey Javascript engine which was introduced in Firefox 3.1alpha, stating that some tests were faster in one engine and some were faster in the other, with Firefox 3.1a faster overall. John Resig, Mozilla's JavaScript evangelist, further commented on the performance of different browsers on Google's own suite, finding Chrome "decimating" other browsers, but he questions whether Google's suite is representative of real programs. He stated that Firefox 3.0 performed poorly on recursion intensive benchmarks, such as those of Google, because the Mozilla team had not implemented recursion-tracing yet.

Chrome also uses DNS prefetching to speed up website lookups.

The Gears team was considering a multithreaded browser (noting that a problem with existing web browser implementations was that they are inherently single-threaded) and Chrome implemented this concept with a multi-process architecture, similar to Loosely Coupled Internet Explorer (LCIE) recently implemented by Internet Explorer 8. By default, a separate process is allocated to each site instance and plugin. This prevents tasks from interfering with each other, which is good for security and stability; an attacker successfully gaining access to one application does not gain access to all, and failure in one application results in a Sad Tab screen of death, similar to the well-known Sad Mac, except only one single tab crashes instead of the whole application. This strategy exacts a fixed per-process cost up front, but results in less memory bloat overall as fragmentation is confined to each process and no longer results in further memory allocations.

Chrome features a process management utility called the Task Manager which allows the user to "see what sites are using the most memory, downloading the most bytes and abusing CPU" (as well as the plugins which run in separate processes) and terminate them. Some users have reported a conflict with Internet Explorer, often resulting in the blue screen error on Windows.

The main user interface includes back, forward, refresh, bookmark, go, and cancel options. A home button can be turned on through options, which takes the user to the nine website previews seen on a new tab. The options are similar to Safari, while the location of the settings is similar to versions of Internet Explorer starting with version 7. The design of the window is based on Windows Vista.

When the window is not maximized, the tab bar appears directly under the title bar. When maximized, the title bar disappears, and instead, the tab bar is shown at the very top of the window. Unlike other browsers such as Internet Explorer or Firefox which also have a full-screen mode that hides the operating system's interface completely, Chrome can only be maximized like a standard Windows application. Therefore, the Windows task bar, notification area, and start menu link still take space at all times unless they have been configured to hide at all times.

Chrome includes Gears, which adds features for web developers typically relating to the building of web applications (including offline support).

Chrome replaces the browser home page which is displayed when a new tab is created with a New Tab Page. This shows thumbnails of the nine most visited web sites along with the sites most often searched, recent bookmarks, and recently closed tabs.

The Omnibox is the URL box at the top of each tab, which combines the functionalities of both URL box and search box. It includes autocomplete functionality, but only will autocomplete URLs that were manually entered (rather than all links), search suggestions, top pages (previously visited), popular pages (unvisited), and text search over history. Search engines also can be captured by the browser when used via the native user interface by pressing Tab.

Popup windows "are scoped to the tab they came from" and will not appear outside the tab unless the user explicitly drags them out.

Chrome uses the WebKit rendering engine to display web pages, on advice from the Android team. Like most browsers, Chrome was extensively tested internally before release with unit testing, "automated user interface testing of scripted user actions" and fuzz testing, as well as WebKit's layout tests (99% of which Chrome is claimed to have passed). New browser builds are automatically tested against tens of thousands of commonly accessed websites inside of the Google index within 20-30 minutes.

Tabs are the primary component of Chrome's user interface and as such, have been moved to the top of the window rather than below the controls. This subtle change contrasts with many existing tabbed browsers which are based on windows and contain tabs. Tabs (including their state) can be transferred seamlessly between window containers by dragging. Each tab has its own set of controls, including the Omnibox.

Chrome allows users to make local desktop shortcuts that open web applications in the browser. The browser, when opened in this way, contains none of the regular interface except for the title bar, so as not to "interrupt anything the user is trying to do." This allows web applications to run alongside local software (similar to Mozilla Prism and Fluid).

By default, the status bar is hidden whenever it is not being used. However, it appears at the bottom left corner whenever a page is loading and when a hyperlink is hovered over.

For web developers, Chrome features an element inspector similar to the one in Firebug.

Chrome sends details about its usage to Google through both optional and non-optional user tracking mechanisms.

Additionally, for installation, Chrome requires the Google Updater, which periodically connects to Google. However, a standalone version is available from Google that does not require it.

Some of the tracking mechanisms can be optionally enabled and disabled through the installation interface and through the browser's options dialog. A Freeware program called UnChrome has been made to erase the clientID off the hard drive. Unofficial builds, such as SRWare Iron, seek to remove these features from the browser altogether.

As of October 2008, Google Chrome does not support 3rd party extensions.

As of version 3499, Google Chrome has rudimentary Greasemonkey support. This feature is off by default, and may be turned on by launching the application with a specific command-line argument.

On January 8, 2009 Google introduced a new release channels system, whereby now there are three distinct release channels: Stable channel, Beta channel, and Developer preview channel. Before this change, there were only two channels: Beta channel and Developer preview channel. All previous Dev channel users were moved to Beta channel, the reason is that now the new Dev channel builds will be less stable and polished than what Dev channel users have been getting during Google Chrome's Beta period. Now the stable channel will be updated with features and fixes once they have been thoroughly tested in the Beta channel, and the Beta channel will be updated roughly monthly with stable and complete features from the Dev channel. The Dev channel is where ideas get tested (and sometimes fail), and it can be very unstable at times.

Microsoft reportedly "played down the threat from Chrome" and "predicted that most people will embrace Internet Explorer 8." Opera Software said that "Chrome will strengthen the Web as the biggest application platform in the world." Mozilla said that Chrome's introduction into the web browser market comes as "no real surprise", that "Chrome is not aimed at competing with Firefox", and furthermore that it should not affect Google's financing of Firefox.

Chrome’s design bridges the gap between desktop and so-called “cloud computing.” At the touch of a button, Chrome lets you make a desktop, Start menu, or Quick Launch shortcut to any Web page or Web application, blurring the line between what’s online and what’s inside your PC. For example, I created a desktop shortcut for Google Maps. When you create a shortcut for a Web application, Chrome strips away all of the toolbars and tabs from the window, leaving you with something that feels much more like a desktop application than like a Web application or page.

On September 9, 2008, when Chrome still had been in beta, the German Federal Office for Information Security (BSI) issued a statement about their first examination of Chrome, expressing a concern over the prominent download links on Google's German web page, because "beta versions should not be employed for general use applications" and browser manufacturers should provide appropriate instructions regarding the use of pre-released software. They did, however, praise the browser's technical contribution to improving security on the web.

Concern about Chrome's optional usage collection and tracking have been noted in several publications.

On September 11, 2008, a few days after the release of Chrome's source code, Scott Hanselman noticed some incriminating lines of comment in Chrome's code. This was further pushed into limelight by the Ars Technica article Chrome antics: did Google reverse-engineer Windows?. Google later responded to this discovery, denying reverse-engineering by themselves and referring to previously documented, although not official, techniques.

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Gmail

Gmail is a free POP3 and IMAP webmail service provided by Google. In the United Kingdom and Germany it is officially called Google Mail.

Gmail launched on April 1, 2004 as an invitation-only beta release and became available to the general public on February 7, 2007. Although over 100 million users have taken advantage of stable releases for years, to this day the service remains in beta status.

With an initial storage capacity offer of 1 GB per user, Gmail significantly increased the webmail standard for free storage from the 2 to 4MB its competitors offered at that time. The service currently offers over 7300 MB of free storage with additional storage ranging from 10 GB to 400 GB available for $20 to $500 (US) per year.

Gmail has a search-oriented interface and a "conversation view" similar to an Internet forum. Software developers know Gmail for its use of the Ajax programming technique.

Gmail runs on Google Servlet Engine and Google GFE/1.3 which run on Linux.

The Gmail service currently provides more than 7300 MB of free storage. Users can rent additional storage (shared between Picasa Web Albums and Gmail) from 10 GB (US$20/year) to 400 GB (US$500/year).

In April 2005 Gmail engineer Rob Siemborski stated that Google would keep increasing storage by the second as long as it had enough space on its servers. On October 12, 2007, Google ramped up the storage counter to 5.37 MB per hour.

Approximately a week later, the counter went back down to 1.12 MB per hour. On January 4, 2008, the counter went down to about 3.35 MB per day, or 0.14 MB per hour. From October 2008, the counter went down to about 353.9 KB per day.

The Gmail Labs feature, introduced on June 5, 2008, allows users to test new or experimental features of Gmail, such as bookmarking of important e-mail messages, custom keyboard-shortcuts and games.

Users can enable or disable Labs features selectively and provide feedback about each of them. This allows Gmail engineers to obtain user input about new features to improve them and also to assess their popularity and whether they merit developing into regular Gmail features. All Labs features are experimental and are subject to termination at any time. Labs features can only be used in the English language interface of Gmail.

On December 10, 2008, Gmail added support for SMS Messaging through its integrated Chat.

On January 28, 2009, Gmail added support for offline access through its integration with Gears.

Gmail's spam filtering features a community-driven system: when any user marks an email as spam, this provides information to help the system identify similar future messages for all Gmail users.

The Gmail interface is unique amongst webmail systems for several reasons. Most evident to users are its search-oriented features and means of managing e-mail in a "conversation view" that is similar to an Internet forum.

Gmail was a project started by Google developer Paul Buchheit several years before it was announced to the public. Initially only Google employees could use the e-mail client and only internally. Google finally announced Gmail to the public on April 1, 2004.

Before its acquisition by Google, the gmail.com domain name was used by a free e-mail service offered by Garfield.com, online home of the comic strip Garfield. After moving to a different domain, that service has since been discontinued.

The domain gmail.com is unavailable in certain countries, in which cases users are able to use the domain googlemail.com. The Gmail service does not discriminate between these two domains for incoming e-mails, therefore a user with the address "john.doe@googlemail.com" will receive mail sent to "john.doe@gmail.com", and vice-versa. Accordingly, users obliged to use the googlemail.com domain are unable to select addresses already chosen by gmail.com users.

On April Fools' Day 2007, Google made fun of Gmail by introducing "Gmail Paper", where a user could click a button and Gmail would purportedly mail an ad-supported hard copy for free.

On April Fools' Day 2008, Google introduced a fake service named Gmail Custom Time, which would allegedly allow a user to send up to ten e-mails per year with forged timestamps. The hoax stated that by bending spacetime on the Google servers, the e-mails actually get routed through the fourth dimension of time itself before reaching their intended recipient.

Gmail's JavaScript front-end was rewritten in late summer and early fall of 2007 and was released to users starting on October 29, 2007. The new version had a redesigned contacts section, quick contacts box and chat popups, which were added to names in the message list as well as the contact list. The contacts application is integrated into other Google services, such as Google Docs. Users granted access to the new version were given a link at the top-right corner which read "Newer Version". As of December 2007, most new registrations in English (US) along with most pre-existing accounts are given the new interface by default when supported. There remains the option to downgrade via a link labelled "Older Version".

These coding changes mean that only users of Internet Explorer 7, Firefox 2, Google Chrome and Safari 3.0 (or more recent versions) can fully use the new code. Internet Explorer 5.5+, Netscape 7.1+, Mozilla 1.4+, Firefox 0.8, Safari 1.3 and some other browsers will give limited functionality. Other browsers may be redirected to the basic-HTML-only version of Gmail.

During the week of January 18, 2008, Google released an update that changed the way Gmail loads JavaScript. This caused the failure of some third-party extensions.

On December 12, 2008, Gmail added support for faster PDF viewing within the browser.

Google automatically scans e-mails to add context-sensitive advertisements to them. Privacy advocates raised concerns that the plan involved scanning their personal, assumed private, e-mails, and that this was a security problem. Allowing e-mail content to be read, even by a computer, raises the risk that the expectation of privacy in e-mail will be reduced. Furthermore, e-mail that non-subscribers choose to send to Gmail accounts is scanned by Gmail as well and these senders did not agree to Gmail's terms of service or privacy policy. Google can change its privacy policy unilaterally and Google is technically able to cross-reference cookies across its information-rich product line to make dossiers on individuals. However, most e-mail systems make use of server-side content scanning in order to check for spam.

Privacy-advocates also regard the lack of disclosed data retention and correlation policies as problematic. Google has the ability to combine information contained in a person's e-mails with information about their Internet searches. Google has not confirmed how long such information would be kept and how it could be used. One of the concerns is that it could be of interest to law enforcement agencies. More than 30 privacy and civil liberties organizations have urged Google to suspend Gmail service until these issues are resolved.

As part of Gmail's privacy policies, Google states that Gmail will refrain from displaying ads next to potentially sensitive messages. Content that suppresses ads includes news about a tragedy, an e-mail about catastrophic events and death announcements. Critics argue that the fact remains that these e-mails are being scanned in order for Gmail's systems to identify the fact that the e-mail is of this type.

Gmail does not allow users to send or receive executable files or archives containing executable files if it recognises the file extension as one used for executable files or archives.

Tech-savvy users who are not prone to casual errors report loss of random messages in random amounts.

By design, Gmail does not deliver all of a user's e-mails. When downloading mail through POP or IMAP access, Gmail fails to deliver messages that users have sent to themselves. It also does not deliver to a user's inbox (via any access interface) those messages that users have sent to mailing lists and which they might expect to receive back via the mailing list.

Gmail filters cannot use custom header names. This limitation had a significant impact before Gmail added support for identifying incoming messages sent to a mailing list: some mailing list manager programs, such as the Mailman used by SourceForge, add a custom header to the messages they distribute, but do not change the "Subject". Gmail filters can check for a string in the "Subject", but not in a custom header.

Gmail has been unavailable on several occasions. On February 24, 2009, the Gmail service was offline for 2.5 hours, preventing millions of users from accessing their accounts. People who rely entirely on Gmail for business purposes complained about these outages.

Gmail only sorts e-mail in conversations (or "threading"), which is a problem for large conversations. For example, if a user sends a query to a large group of people, all of the responses are stored in a single conversation that is impossible to break apart. There is no way to search for responses from one user without getting the entire conversation. Archiving, labeling and some other special operations on just one part of a conversation are not possible.

With the current Gmail implementation, any email sent through the Gmail interface will include the Gmail.com address as the "sender", even if the sending account is a custom email account. For example, an email sent from an external account via the Gmail interface will display to an e-mail client user as From user@gmail.com on behalf of user@OtherDomainEmailAddress.com. By exposing the Gmail account name, Google claims that this will "help prevent mail from being marked as spam". A number of Gmail users have complained that this implementation is both a privacy concern and a professionalism problem.

Gmail was ranked second in PC World's "100 Best Products of 2005," behind Mozilla Firefox. Gmail also won 'Honorable Mention' in the Bottom Line Design Awards 2005.

Gmail has drawn many favorable reviews from users for generous space quotas and unique organization.

On October 19, 2005, Google voluntarily converted the United Kingdom version of Gmail to Google Mail because of a dispute with the UK company, Independent International Investment Research.

Users who registered before the switch to Google Mail were able to keep their Gmail address, although the Gmail logo was replaced with a Google Mail logo. Users who signed up after the name change receive a googlemail.com address, although a reverse of either in the sent email will still deliver it to the same place.

On July 4, 2005, Google announced that Gmail Deutschland would be rebranded to Google Mail. From that point forward, visitors originating from an IP address determined to be in Germany would be forwarded to googlemail.com where they could obtain an e-mail address containing the new domain. Any German user who wants a gmail.com address must sign up for an account through a proxy. German users who were already registered were allowed to keep their old addresses.

The German naming issue is due to a trademark dispute between Google and Daniel Giersch. Daniel Giersch owns a company called "G-mail" which provides the service of printing out e-mail from senders and sending the print-out via postal mail to the intended recipients. On January 30, 2007, the EU's Office for Harmonization in the Internal Market ruled in favor of Giersch.

Google spoofed "offering" the same service in the Gmail Paper April Fool's Day joke in 2007.

In February 2007, Google filed legal action against the owners of gmail.pl, a fake poet group known in full as Grupa Młodych Artystów i Literatów abbreviated GMAiL (literally, "Group of Young Artists and Writers"). Łódzka Giełda Komputerowa (Łódź Computer Market), a corporation which sells computer-accessories, had registered the gmail.pl domain for promotional purposes. The Arbitration Tribunal canceled the action for "procedural reasons".

An information-technology company in mainland China named ISM Technologies (Chinese: 爱思美) has owned and operated a web portal from the domain gmail.cn since 2003.

A Russian free webmail service called gmail.ru owns the "GMail" trademark in the Russian Federation.

The gmail.ru domain name dates from January 27, 2003.

After Gmail's initial development and launch, many existing web mail services quickly increased their storage capacity.

For example, Hotmail increased space for some users 2 MB to 25 MB, with 250 MB after 30 days, and 2 GB for Hotmail Plus accounts. Yahoo! Mail went from 4 MB to 100 MB and 2 GB for Yahoo! Mail Plus accounts. Yahoo! Mail storage then increased to 250 MB and in late April 2005 to 1 GB. Yahoo! Mail announced that it would be providing "unlimited" storage to all its users in March 2007 and began providing it in May 2007.

These were all seen as moves to stop existing users from switching to Gmail and to capitalize on the newly rekindled public interest in web mail services. The desire to catch up was especially noted in the case of MSN's Hotmail, which upgraded its e-mail storage from 250 MB to the new Windows Live Hotmail which includes 5 GB of storage. As of November 2006, MSN Hotmail upgraded all free accounts to 1 GB of storage.

In August 2005 AOL started providing all AIM screen names with their own e-mail accounts with 2 GB of storage.

Another source of competition for Gmail came from 30Gigs who, as their name implied, offered 30 gigabytes of storage, initially through invitation only, starting in late 2006. However in November 2007, 30Gigs' service was discontinued.

The Gmail system flags as dormant every Gmail account which remains inactive for six months. After a further three months, for a total of nine months dormancy, the system may delete such accounts. Other webmail services have different, often shorter, times for marking an account as inactive. Yahoo! Mail deactivates dormant accounts after four months, as does Windows Live Hotmail.

As well as increasing storage limits following the launch of Gmail, Yahoo! Mail and Hotmail also enhanced their e-mail interfaces. During 2005 Yahoo! Mail and Hotmail matched Gmail's attachment size of 10 MB. Following the footsteps of Gmail, Yahoo! launched the Yahoo! Mail Beta service and Microsoft launched Windows Live Hotmail, both incorporating Ajax interfaces. Google increased the maximum attachment size to 20 MB in May 2007.

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Greasemonkey

Greasemonkey is a Mozilla Firefox add-on that allows users to install scripts that make on-the-fly changes to most HTML-based web pages. As Greasemonkey scripts are persistent, the changes made to the web pages are executed every time the page is opened, making them effectively permanent for the user running the script. Greasemonkey can be used for adding new functions to web pages (for example, embedding price comparison in Amazon.com web pages), fixing rendering bugs, combining data from multiple webpages, and numerous other purposes.

Most Greasemonkey user scripts are written by hand, using site-specific JavaScript code that manipulates the contents of a web page using the Document Object Model interface. userscripts.org maintains a database of Greasemonkey scripts, and for each it lists the URLs of web pages to which the scripts pertain. When the user loads a matching page, Greasemonkey invokes the relevant scripts, which can then add to the page, delete parts of it, or move parts around. Greasemonkey scripts can also poll external HTTP resources via a non-domain-restricted XMLHTTP request. Greasemonkey scripts are named somename.user.js, and Greasemonkey automatically detects and offers to install any such script, when a URL ending in that suffix is loaded. In addition to JavaScript code, Greasemonkey scripts contain limited optional metadata, which specifies the name of the script, a description, a namespace URL used to differentiate identically named scripts, and URL patterns for which the script is intended to be invoked or not.

Writing a Greasemonkey script is similar to writing JavaScript for a web page, with some additional restrictions imposed by the security provisions of Mozilla's XPCNativeWrappers. Compared to writing a full-fledged Firefox extension, user scripting is a very modest step up in complexity from basic web programming.

For an interactive approach to modifying web pages that does not require programming, see Platypus , a Firefox extension that allows you to modify pages by clicking on objects.

Greasemonkey is available for Firefox, Flock and Epiphany. The Epiphany Greasemonkey extension is part of the Epiphany-extensions package. However, this extension is not fully compatible as of release 2.15.1, since some Greasemonkey API functions (e.g. GM_getValue) are unsupported. There are also custom versions for SeaMonkey and Songbird.

Version 8 and upwards of Opera also have user scripting functionality. Both Opera and Firefox support the W3C DOM. Opera is capable of running many Greasemonkey user scripts.

GreaseKit (formerly Creammonkey) and PithHelmet (shareware) are similar tools for the Mac OS version of the Safari browser, along with other WebKit based applications such as MailPlane.

Konqueror Userscript is a webpage manipulation tool for KDE's Konqueror browser that aims for compatibility with Greasemonkey scripts and metadata. It is available as a KPart.

For Internet Explorer, similar function is offered by IE7pro, iMacros, Trixie (last updated 2005), Turnabout (last updated 2006) and Greasemonkey for IE (last updated 2006). Turnabout used to be open source software (under the BSD License), but as of September 2006, the source code is no longer available.

As of November 2008, there is only limited support for Greasemonkey scripts in the Chrome beta (since build 3499). It is disabled by default, but can be enabled by adding --enable-greasemonkey as a startup parameter. As there is currently no method to load scripts within Chrome, scripts must be placed into the C:\scripts directory for Chrome, and into the "user data directory" for newer builds of Chromium. Chrome ignores @include metadata within the scripts, so the scripts are executed for all domains/pages. On the other hand, Chromium honors the @include directives and executes the scripts only for the domains/pages specified. However, the pre-beta version of Google Chrome 2.0, released in early January 2009, is reported to support Greasemonkey.

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V8 (JavaScript engine)

The V8 JavaScript engine is an open source JavaScript engine developed by Google in Denmark and shipping with the Google Chrome browser.

It increases performance by compiling JavaScript to native machine code before running it, rather than to a bytecode or interpreting it and by employing optimization techniques like inline caching. Thus, JavaScript applications will run at the speed of a compiled binary.

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SRWare Iron

SRWare Iron, or simply Iron, is a free and open-source web browser implementation of Google Chrome which primarily aims to eliminate usage tracking and other privacy violating functionality that Chrome includes. Iron is developed by SRWare and based on Chromium.

Iron includes other notable unique features. In contrast to Chrome, it implements the latest version of the WebKit rendering engine, and includes a built-in ad blocker. A common speculation is that Chrome's future ad blocking feature will not work properly because it might exclude Google-affliated ads.

Iron was first released on September 18, 2008, 16 days after Chrome's initial release. According to Iron's developers, Chromium's source code was extensively modified in order to remove any privacy related functionality.

On January 22, 2009 a developer preview was released.

The following usage tracking related features, do not exist in Iron, in contrast to their implementation in Google Chrome.

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