A microformat (sometimes abbreviated μF) is a web-based approach to semantic markup which seeks to re-use existing HTML/XHTML tags to convey metadata and other attributes in web pages and other contexts that support (X)HTML, such as RSS. This approach allows software to process information intended for end-users (such as contact information, geographic coordinates, calendar events, and similar information) automatically.
Although the content of web pages is technically already capable of "automated processing", and has been since the inception of the web, such processing is difficult because the traditional markup tags used to display information on the web do not describe what the information means. Microformats can bridge this gap by attaching semantics, and thereby obviate other, more complicated, methods of automated processing, such as natural language processing or screen scraping. The use, adoption and processing of microformats enables data items to be indexed, searched for, saved or cross-referenced, so that information can be reused or combined.
As of 2010[update], microformats allow the encoding and extraction of events, contact information, social relationships and so on. Established microformats such as hCard are published on the web more than alternatives like schema and RDFa.
Microformats emerged as part of a grassroots movement to make recognizable data items (such as events, contact details or geographical locations) capable of automated processing by software, as well as directly readable by end-users. Link-based microformats emerged first. These include vote links that express opinions of the linked page, which search engines can tally into instant polls.
CommerceNet, a nonprofit organization that promotes electronic commerce on the Internet, has helped sponsor and promote the technology and support the microformats community in various ways. CommerceNet also helped co-found the Microformats.org community site.
Neither CommerceNet nor Microformats.org operates as a standards body. The microformats community functions through an open wiki, a mailing list, and an Internet relay chat (IRC) channel. Most of the existing microformats originated at the Microformats.org wiki and the associated mailing list by a process of gathering examples of web- publishing behaviour, then codifying it. Some other microformats (such as rel=nofollow and unAPI) have been proposed, or developed, elsewhere.
Technical overview 
XHTML and HTML standards allow for the embedding and encoding of semantics within the attributes of markup tags. Microformats take advantage of these standards by indicating the presence of metadata using the following attributes:
- relationship, description of the target address in an anchor-element (
<a href=... rel=...>...</a>)
- reverse relationship, description of the referenced document (in one case, otherwise deprecated in microformats)
For example, in the text "The birds roosted at 52.48, -1.89" is a pair of numbers which may be understood, from their context, to be a set of geographic coordinates. With wrapping in spans (or other HTML elements) with specific class names (in this case
longitude, all part of the geo microformat specification):
The birds roosted at <span class="geo"> <span class="latitude">52.48</span>, <span class="longitude">-1.89</span> </span>
software agents can recognize exactly what each value represents and can then perform a variety of tasks such as indexing, locating it on a map and exporting it to a GPS device.
In this example, the contact information is presented as follows:
<ul> <li>Joe Doe</li> <li>The Example Company</li> <li>604-555-1234</li> <li><a href="http://example.com/">http://example.com/</a></li> </ul>
With hCard microformat markup, that becomes:
<ul class="vcard"> <li class="fn">Joe Doe</li> <li class="org">The Example Company</li> <li class="tel">604-555-1234</li> <li><a class="url" href="http://example.com/">http://example.com/</a></li> </ul>
Here, the formatted name (
fn), organisation (
org), telephone number (
tel) and web address (
url) have been identified using specific class names and the whole thing is wrapped in
class="vcard", which indicates that the other classes form an hCard (short for "HTML vCard") and are not merely coincidentally named. Other, optional, hCard classes also exist. Software, such as browser plug-ins, can now extract the information, and transfer it to other applications, such as an address book.
Specific microformats 
Several microformats have been developed to enable semantic markup of particular types of information. However, only hCard and hCalendar have been ratified, the others remaining as drafts:
- hAtom – for marking up Atom feeds from within standard HTML
- hCalendar – for events
- hCard – for contact information; includes:
- hMedia - for audio/video content 
- hNews - for news content
- hProduct – for products
- hRecipe - for recipes and foodstuffs.
- hResume – for resumes or CVs
- hReview – for reviews
- rel-directory – for distributed directory creation and inclusion
- rel-enclosure – for multimedia attachments to web pages
- rel-license – specification of copyright license
- rel-nofollow, an attempt to discourage third-party content spam (e.g. spam in blogs)
- rel-tag – for decentralized tagging (Folksonomy)
- xFolk – for tagged links
- XHTML Friends Network (XFN) – for social relationships
- XOXO – for lists and outlines
Uses of microformats 
Using microformats within HTML code provides additional formatting and semantic data that applications can use. For example, applications such as web crawlers can collect data about on-line resources, or desktop applications such as e-mail clients or scheduling software can compile details. The use of microformats can also facilitate "mash ups" such as exporting all of the geographical locations on a web page into (for example) Google Maps to visualize them spatially.
Several browser extensions, such as Operator for Firefox and Oomph for Internet Explorer, provide the ability to detect microformats within an HTML document. When hCard or hCalendar are involved, such browser extensions allow to export them into formats compatible with contact management and calendar utilities, such as Microsoft Outlook. When dealing with geographical coordinates, they allow to send the location to maps applications such as Google Maps. Yahoo! Query Language can be used to extract microformats from web pages. On 12 May 2009, Google announced that they would be parsing the hCard, hReview and hProduct microformats, and using them to populate search result pages. They have since extended this to use hCalendar for events and hRecipe for cookery recipes. Similarly, microformats are also consumed by Bing and Yahoo!. Together, these are the world's top three search engines.
Alex Faaborg summarizes the arguments for putting the responsibility for microformat user interfaces in the web browser rather than making more complicated HTML:
- Only the web browser knows what applications are accessible to the user and what the user's preferences are
- It lowers the barrier to entry for web site developers if they only need to do the markup and not handle "appearance" or "action" issues
- Retains backwards compatibility with web browsers that don't support microformats
- The web browser presents a single point of entry from the web to the user's computer, which simplifies security issues
Evaluation of microformats 
Various commentators have offered review and discussion on the design principles and practical aspects of microformats. Additionally, microformats have been compared to other approaches that seek to serve the same or similar purpose. From time to time, there is criticism of a single, or all, microformats. Documented efforts to advocate both the spread and use of microformats are known to exist as well. Opera Software CTO and CSS creator Håkon Wium Lie said in 2005 "We will also see a bunch of microformats being developed, and that’s how the semantic web will be built, I believe." However, as of August 2008, Toby Inkster, author of the "Swignition" (formerly "Cognition") microformat parsing service pointed out that no new microformat specifications had been published since 2005.
Design principles 
Computer scientist and entrepreneur, Rohit Khare stated that reduce, reuse, and recycle is "shorthand for several design principles" that motivated the development and practices behind microformats.:71-72 These aspects can be summarized as follows:
- Reduce: favor the simplest solutions and focus attention on specific problems;
- Reuse: work from experience and favor examples of current practice;
- Recycle: encourage modularity and the ability to embed, valid XHTML can be reused in blog posts, RSS feeds, and anywhere else you can access the web.
Because some microformats make use of title attribute of HTML's
abbr element to conceal machine-readable data (particularly date-times and geographical coordinates) in the "abbr design pattern", the plain text content of the element is inaccessible to those screen readers that expand abbreviations. In June 2008, the BBC announced that it would be dropping use of microformats using the
abbr design pattern because of accessibility concerns.
Comparison with alternative approaches 
Microformats are not the only solution for providing "more intelligent data" on the web. Alternative approaches exist and are under development as well. For example, the use of XML markup and standards of the Semantic Web are cited as alternative approaches. Some contrast these with microformats in that they do not necessarily coincide with the design principles of "reduce, reuse, and recycle", at least not to the same extent.
One advocate of microformats, Tantek Çelik, characterized a problem with alternative approaches:
|“||Here's a new language we want you to learn, and now you need to output these additional files on your server. It's a hassle. (Microformats) lower the barrier to entry.||”|
For some applications the use of other approaches may be valid. If one wishes to use microformat-style embedding but the type of data one wishes to embed does not map to an existing microformat, one can use RDFa to embed arbitrary vocabularies into HTML, for example: embedding domain-specific scientific data on the Web like zoological or chemical data where no microformat for such data exists. Furthermore, standards such as W3C's GRDDL allow microformats to be converted into data compatible with the Semantic Web.
Another advocate of microformats, Ryan King, put the compatibility of microformats with other approaches this way:
|“||Microformats provide an easy way for many people to contribute semantic data to the web. With GRDDL all of that data is made available for RDF Semantic Web tools. Microformats and GRDDL can work together to build a better web.||”|
See also 
- Embedded RDF
- Intelligent agents
- Microdata (HTML5)
- S5 (file format)
- Simple HTML Ontology Extensions
- Tag (metadata)
- Web crawlers
- "Class Names Across All Microformats". Microformats.org. 2007-09-23. Retrieved 2008-09-06.
- "What’s the Next Big Thing on the Web? It May Be a Small, Simple Thing -- Microformats". Knowledge@Wharton. Wharton School of the University of Pennsylvania. 2005-07-27.
- "Web Data Commons: Extracting Structured Data from the Common Web Crawl". 2012-03-22: Extraction results from the 2012 Common Crawl corpus available for download, 2012-03-13: Extraction results from the 2009/2010 Common Crawl corpus available for download. 2012-03-22. Retrieved 2012-04-09.
- In this context, the definition of "end-user" includes a person reading a web page on a computer screen or mobile device, or an assistive technology software program such as a screen reader.
- Khare, Rohit (January/February 2006). "Microformats: The Next (Small) Thing on the Semantic Web?". IEEE Internet Computing (IEEE Computer Society) 10 (1): 68–75. doi:10.1109/MIC.2006.13. Retrieved 2008-09-06.
- ""rel" attribute frequently asked questions". Microformats.org. 2008-08-06. Retrieved 2008-09-06.
- hMedia · Microformats Wiki
- Ultimate Guide to Microformats: Reference and Examples
- rel-directory · Microformats Wiki
- rel="enclosure" · Microformats Wiki
- rel="license" · Microformats Wiki
- rel="tag" · Microformats Wiki
- Heilman, Chris (2009-01-19). "Retrieving and displaying data from Wikipedia with YQL". Yahoo Developer Network. Yahoo. Retrieved 2009-01-19.
- Goel, Kavi; Ramanathan V. Guha, Othar Hansson (2009-05-12). "Introducing Rich Snippets". Google Webmaster Central Blog. Google. Retrieved 2009-05-25.
- Gong, Jun; Kosuke Suzuki, Yu Watanabe (2010-04-13). "Better recipes on the web: Introducing recipe rich snippets". Google. Retrieved 17 March 2011.
- "Bing Introducing Schema.org: Bing, Google and Yahoo Unite to Build the Web of Objects - Search Blog - Site Blogs - Bing Community". Bing. 2011-06-02. Retrieved 2 June 2011.
- "Introducing schema.org: A Collaboration on Structured Data". 2011-06-02. Retrieved 2 June 2011.
- "Top 5 Search Engines from Oct to Dec 10 | StatCounter Global Stats". StatCounter. Retrieved 17 January 2011.
- "Bill Gates at Mix06 – "We need microformats"". 2006-03-20. Retrieved 2008-09-06. "We need microformats and to get people to agree on them. It is going to bootstrap exchanging data on the Web… …we need them for things like contact cards, events, directions…"
- Microformats – Part 4: The User Interface of Microformat Detection « Alex Faaborg
- "Criticism". Microformats.org. 2007-03-24. Retrieved 2007-08-15.
- "Advocacy". Microformats.org. 2008-08-27. Retrieved 2007-08-15.
- "Spread Microformats". Microformats.org. 2008-08-29. Retrieved 2007-08-15. This includes community resources for marketing microformats such as buttons, banners, wallpaper / desktop screens, logo graphics, etc.
- Holzschlag, Molly E. (2005-03-31). "Interview with Håkon Wium Lie". Molly.com. Retrieved 2007-11-18.
- Inkster, Toby A. (2008-04-22). "More than three years". Microformats.org. Retrieved 2008-08-24.
- Craig, James (2007-04-27). "hAccessibility". Web Standards Project. Retrieved 2007-08-16.
- Smethurst, Michael (2008-06-23). "Removing Microformats from bbc.co.uk/programmes". BBC. Retrieved 2008-08-24.
- "W3C GRDDL Recommendation Bridges HTML/Microformats and the Semantic Web". XML Coverpages. OASIS. 2007-09-13. Retrieved 2007-11-23.
- Allsopp, John (March 2007). Microformats: Empowering Your Markup for Web 2.0. Friends of ED. p. 368. ISBN 978-1-59059-814-6.
- Orchard, Leslie M (September 2005). Hacking RSS and Atom. John Wiley & Sons. p. 602. ISBN 978-0-7645-9758-9.
- Robbins, Jennifer Niederst; Tantek Çelik, Derek Featherstone, Aaron Gustafson (February 2006). Web Design In A Nutshell (Third ed.). O'Reilly Media. p. 826. ISBN 978-0-596-00987-8.
Further reading 
- Suda, Brian (September 2006). Using Microformats. O'Reilly Media. p. 45. ISBN 978-0-596-52821-8.
- Ahmet Soylu, Patrick De Causmaecker, Fridolin Wild Ubiquitous Web for Ubiquitous Environments: The Role of Embedded Semantics, article in Journal of Mobile Multimedia, Vol. 6, No.1, pp. 26–48, (2010). PDF
|Wikimedia Commons has media related to: Microformat screenshots|
- Microformats Primer
- Optimus microformats parser and validator
- A four-part discussion of Microformats, UI issues, and possible presentation in Firefox 3 by Alex Faaborg of Mozilla