WordPress is a free and open-source content management system (CMS) based on PHP and MySQL. WordPress is installed on a web server, which either is part of an Internet hosting service or is a network host itself; the first case might be on a service like WordPress.com, for example, and the second case is a computer running the software package WordPress.org. An example of the second case is a local computer configured to act as its own web server hosting WordPress for single-user testing or learning purposes. Features include a plugin architecture and a template system. WordPress was used by more than 26.4% of the top 10 million websites as of April 2016. WordPress is reportedly the easiest and most popular blogging system in use on the Web, supporting more than 60 million websites.

It was released on May 27, 2003, by its founders, Matt Mullenweg and Mike Little, as a fork of b2/cafelog. WordPress is released under the GPLv2 (or later) licence from the Free Software Foundation.

Overview

WordPress has a web template system using a template processor. Once downloaded, WordPress installation files have a size of about 20 MB.

Themes

WordPress users might instal and switch between different themes. Themes allow users to change the look and functionality of a WordPress website and they can be installed without altering the content or health of the site. Every WordPress website requires at least one theme to be present and every theme should be designed using WordPress standards with structured PHP, valid HTML and Cascading Style Sheets (CSS). Themes might be directly installed using the WordPress "Appearance" administration tool in the dashboard or theme folders might be uploaded via FTP. The PHP, HTML (HyperText Markup Language) and CSS code found in themes can be added to or edited for providing advanced features. WordPress themes are in general classified into two categories, free themes and premium themes. All the free themes are listed in the WordPress theme directory and premium themes are available for purchase from marketplaces and individual WordPress developers. WordPress users might additionally create and develop their own custom themes if they have the knowledge and skill to do so. Underscores has become a popular choice for WordPress advanced theme developers which is designed and maintained by the makers of WordPress themselves. If WordPress users don't have sufficient theme development knowledge they might download and use free WordPress themes.

Plugins

WordPress' plugin architecture allows users to extend the features and functionality of a website or blog. WordPress has over 40,501 plugins available, each of which offers custom functions and features enabling users to tailor their sites to their specific needs. These customizations range from search engine optimization, to client portals used to display private information to logged in users, to content management systems, to content displaying features, such as the addition of widgets and navigation bars. Not all available plugins are always abreast with the upgrades and as a result they might not function properly or might not function at all.

Mobiles

Native applications exist for WebOS, Android, iOS (iPhone, iPod Touch, iPad), Windows Phone, and BlackBerry. These applications, designed by Automattic, allow a limited set of options, which include adding new blog posts and pages, commenting, moderating comments, replying to comments in addition to the ability to view the stats.

Other features

WordPress additionally features integrated link management; a search engine–friendly, clean permalink structure; the ability to assign multiple categories to articles; and support for tagging of posts and articles. Automatic philtres are additionally included, providing standardised formatting and styling of text in articles (for example, converting regular quotes to smart quotes). WordPress additionally supports the Trackback and Pingback standards for displaying links to additional sites that have themselves linked to a post or an article. WordPress blog posts can be edited in HTML, using the visual editor, or using one of a number of plugins that allow for a variety of customised editing features.

Multi-user and multi-blogging

Prior to version 3, WordPress supported one blog per installation, although multiple concurrent copies might be run from different directories if configured to use separate database tables. WordPress Multisites (previously referred to as WordPress Multi-User, WordPress MU, or WPMU) was a fork of WordPress created to allow multiple blogs to exist within one installation but is able to be administered by a centralised maintainer. WordPress MU makes it possible for those with websites to host their own blogging communities, as well as control and moderate all the blogs from a single dashboard. WordPress MS adds eight new data tables for each blog.

As of the release of WordPress 3, WordPress MU has merged with WordPress.

History

b2/cafelog, more commonly known as b2 or cafelog, was the precursor to WordPress. b2/cafelog was estimated to have been installed on approximately 2,000 blogs as of May 2003. It was written in PHP for use with MySQL by Michel Valdrighi, who's now a contributing developer to WordPress. Although WordPress is the official successor, another project, b2evolution, is additionally in active development.

WordPress first appeared in 2003 as a joint effort between Matt Mullenweg and Mike Little to create a fork of b2. Christine Selleck Tremoulet, a friend of Mullenweg, suggested the name WordPress.

In 2004 the licencing terms for the competing Movable Type package were changed by Six Apart, resulting in a large number of of its most influential users migrating to WordPress. By October 2009 the Open Source CMS MarketShare Report concluded that WordPress enjoyed the greatest brand strength of any open-source content management system.

As of January 2015, more than 23.3% of the top 10 million websites now use WordPress.

As of February 2016, WordPress is used by 59.1% of all the websites whose content management system we know. This is 25.8% of all websites.

Release history

Main releases of WordPress are codenamed after well-known jazz musicians, starting after version 1.0.

Legend:Old versionOlder version, still supportedCurrent stable versionLatest preview versionFuture release
VersionCode nameRelease dateNotes
Old version, no longer supported: 0.7noneMay 27, 2003Used the same file structure as its predecessor, b2/cafelog, and continued the numbering from its last release, 0.6. Only 0.71-gold is available for download in the official WordPress Release Archive page.
Old version, no longer supported: 1.0DavisJanuary 3, 2004Added search engine friendly permalinks, multiple categories, dead simple installation and upgrade, comment moderation, XFN support, Atom support.
Old version, no longer supported: 1.2MingusMay 22, 2004Added support of Plugins; which same identification headers are used unchanged in WordPress releases as of 2011.
Old version, no longer supported: 1.5StrayhornFebruary 17, 2005Added a range of vital features, such as ability to manage static pages and a template/Theme system. It was additionally equipped with a new default template (code named Kubrick). designed by Michael Heilemann.
Old version, no longer supported: 2.0DukeDecember 31, 2005Added rich editing, better administration tools, image uploading, faster posting, improved import system, fully overhauled the back end, and various improvements to Plugin developers.
Old version, no longer supported: 2.1EllaJanuary 22, 2007Corrected security issues, redesigned interface, enhanced editing tools (including integrated spell cheque and auto save), and improved content management options.
Old version, no longer supported: 2.2GetzMay 16, 2007Added widget support for templates, updated Atom feed support, and speed optimizations.
Old version, no longer supported: 2.3DexterSeptember 24, 2007Added native tagging support, new taxonomy system for categories, and easy notification of updates, fully supports Atom 1.0, with the publishing protocol, and a few much needed security fixes.
Old version, no longer supported: 2.5BreckerMarch 29, 2008Major revamp to the dashboard, dashboard widgets, multi-file upload, extended search, improved editor, improved plugin system and more.
Old version, no longer supported: 2.6TynerJuly 15, 2008Added new features that made WordPress a more powerful CMS: it can now track changes to every post and page and allow easy posting from anywhere on the web.
Old version, no longer supported: 2.7ColtraneDecember 11, 2008Administration interface redesigned fully, added automatic upgrades and installing plugins, from within the administration interface.
Old version, no longer supported: 2.8BakerJune 10, 2009Added improvements in speed, automatic installing of themes from within administration interface, introduces the CodePress editor for syntax highlighting and a redesigned widget interface.
Old version, no longer supported: 2.9CarmenDecember 19, 2009Added global undo, built-in image editor, batch plugin updating, and a large number of less visible tweaks.
Old version, no longer supported: 3.0TheloniousJune 17, 2010Added a new theme APIs, merge WordPress and WordPress MU, creating the new multi-site functionality, new default theme "Twenty Ten" and a refreshed, lighter admin UI.
Old version, no longer supported: 3.1ReinhardtFebruary 23, 2011Added the Admin Bar, which is displayed on all blog pages when an admin is logged in, and Post Format, best explained as a Tumblr like micro-blogging feature. It provides easy access to a large number of critical functions, such as comments and updates. Includes internal linking abilities, a newly streamlined writing interface, and a large number of additional changes.
Old version, no longer supported: 3.2GershwinJuly 4, 2011Focused on making WordPress faster and lighter. Released only four months after version 3.1, reflecting the growing speed of development in the WordPress community.
Old version, no longer supported: 3.3SonnyDecember 12, 2011Focused on making WordPress friendlier for beginners and tablet computer users.
Old version, no longer supported: 3.4GreenJune 13, 2012Focused on improvements to Theme customization, Twitter integration and several minor changes.
Old version, no longer supported: 3.5ElvinDecember 11, 2012Support for the Retina Display, colour picker, new default theme "Twenty Twelve", improved image workflow.
Old version, no longer supported: 3.6OscarAugust 1, 2013New default theme "Twenty Thirteen", admin enhancements, post formats UI update, menus UI improvements, new revision system, autosave and post locking.
Older version, yet still supported: 3.7BasieOctober 24, 2013Automatically apply maintenance and security updates in the background, stronger password recommendations, support for automatically installing the right language files and keeping them up to date.
Older version, yet still supported: 3.8ParkerDecember 12, 2013Improved admin interface, responsive design for mobile devices, new typography using Open Sans, admin colour schemes, redesigned theme management interface, simplified main dashboard, Twenty Fourteen magazine style default theme, second release using "Plugin-first development process".
Older version, yet still supported: 3.9SmithApril 16, 2014Improvements to editor for media, live widget and header previews, new theme browser.
Older version, yet still supported: 4.0BennySeptember 4, 2014Improved media management, embeds, writing interface, easy language change, theme customizer, plugin discovery and compatibility with PHP 5.5 and MySQL 5.6.
Older version, yet still supported: 4.1DinahDecember 18, 2014Twenty Fifteen as the new default theme, distraction-free writing, easy language switch, Vine embeds and plugin recommendations.
Older version, yet still supported: 4.2PowellApril 23, 2015New "Press This" features, improved characters support, emoji support, improved customizer, new embeds and updated plugin system.
Older version, yet still supported: 4.3BillieAugust 18, 2015Focus on mobile experience, better passwords and improved customizer.
Older version, yet still supported: 4.4CliffordDecember 8, 2015Introduction of Twenty Sixteen theme, and improved responsive images and embeds.
Older version, yet still supported: 4.5ColemanApril 12, 2016Added inline linking, formatting shortcuts, live responsive previews, and additional updates under the hood.
Current stable version: 4.6PepperAugust 16, 2016Added streamlined updates, native fonts, editor improvements with inline link checker and content recovery, and additional updates under the hood.
Future release: 4.7NoneDecember, 2016The release is targeted for December 2016.

Future

Matt Mullenweg has stated that the future of WordPress is in social, mobile, and as an application platform.

Vulnerabilities

Many security issues have been uncovered in the software, particularly in 2007, 2008, and 2015. According to Secunia, WordPress in April 2009 had 7 unpatched security advisories (out of 32 total), with a maximum rating of "Less Critical". Secunia maintains an up-to-date list of WordPress vulnerabilities.

In January 2007, a large number of high-profile search engine optimization (SEO) blogs, as well as a large number of low-profile commercial blogs featuring AdSense, were targeted and attacked with a WordPress exploit. A separate vulnerability on one of the project site's web servers allowed an attacker to introduce exploitable code in the form of a back door to a few downloads of WordPress 2.1.1. The 2.1.2 release addressed this issue; an advisory released at the time advised all users to upgrade immediately.

In May 2007, a study revealed that 98 percent of WordPress blogs being run were exploitable because they were running outdated and unsupported versions of the software. In part to mitigate this problem, WordPress made updating the software a much easier, "one click" automated process in version 2.7 (released in December 2008). Notwithstanding the filesystem security settings required to enable the update process can be an additional risk.

In a June 2007 interview, Stefan Esser, the founder of the PHP Security Response Team, spoke critically of WordPress' security track record, citing problems with the application's architecture that made it unnecessarily difficult to write code that's secure from SQL injection vulnerabilities, as well as a few additional problems.

In June 2013, it was found that a few of the 50 most downloaded WordPress plugins were vulnerable to common Web attacks such as SQL injection and XSS. A separate inspection of the top-10 e-commerce plugins showed that 7 of them were vulnerable.

In an effort to promote better security, and to streamline the update experience overall, automatic background updates were introduced in WordPress 3.7.

Individual installations of WordPress can be protected with security plugins that prevent user enumeration, hide resources and thwart probes. Users can additionally protect their WordPress installations by taking steps such as keeping all WordPress installation, themes, and plugins updated, using only trusted themes and plugins, editing the site's .htaccess file to prevent a large number of types of SQL injection attacks and block unauthorised access to sensitive files. It is especially important to keep WordPress plugins updated because would-be hackers can easily list all the plugins a site uses, and then run scans searching for any vulnerabilities against those plugins. If vulnerabilities are found, they might be exploited to allow hackers to upload their own files (such as a PHP Shell script) that collect sensitive information.

Developers can additionally use tools to analyse potential vulnerabilities, including WPScan, WordPress Auditor and WordPress Sploit Framework developed by 0pc0deFR. These types of tools research known vulnerabilities, such as a CSRF, LFI, RFI, XSS, SQL injection and user enumeration. Notwithstanding not all vulnerabilities can be detected by tools, so it is advisable to cheque the code of plugins, themes and additional add-ins from additional developers.

In March 2015, it was reported by a large number of security experts and SEOs including Search Engine Land that a SEO plugin for WordPress called Yoast which is used by more than 14 million users worldwide has a vulnerability which can lead to an exploit where hackers can do a Blind SQL injection.

To fix that issue they immediately introduced a newer version 1.7.4 of the same plugin to avoid any disturbance on web because of the security lapse that the plugin had.

WordPress' minimum PHP version requirement is PHP 5.2, which was released on January 6, 2006, 10 years ago, and which has been unsupported by the PHP Group and not received any security patches after January 6, 2011, 5 years ago.

Development and support

Key developers

Matt Mullenweg and Mike Little were cofounders of the project. The core lead developers include Helen Hou-Sandí, Dion Hulse, Mark Jaquith, Matt Mullenweg, Andrew Ozz, and Andrew Nacin.

WordPress is additionally developed by its community, including WP testers, a group of volunteers who test each release. They have early access to nightly builds, beta versions and release candidates. Errors are documented in a special mailing list, or the project's Trac tool.

Though largely developed by the community surrounding it, WordPress is closely associated with Automattic, the company founded by Matt Mullenweg. On September 9, 2010, Automattic handed the WordPress trademark to the newly created WordPress Foundation, which is an umbrella organisation supporting WordPress.org (including the software and archives for plugins and themes), bbPress and BuddyPress.

WordCamp developer and user conferences

WordCamps are casual, locally organised conferences covering everything related to WordPress. The first such event was WordCamp 2006 in August 2006 in San Francisco, which lasted one day and had over 500 attendees. The first WordCamp outside San Francisco was held in Beijing in September 2007. Since then, there have been over 507 WordCamps in over 207 cities in 48 different countries around the world. WordCamp San Francisco 2014 was the last official annual conference of WordPress developers and users taking place in San Francisco, having now been replaced with WordCamp US.

Support

WordPress' primary support website is WordPress.org. This support website hosts both WordPress Codex, the online manual for WordPress and a living repository for WordPress information and documentation, and WordPress Forums, an active online community of WordPress users.