What Is Metadata?

Metadata is data about data. In other words, it's information that's used to describe the data that's contained in something like a web page, document, or file. Another way to think of metadata is as a short explanation or summary of what the data is.

A simple example of metadata for a document might include a collection of information like the author, file size, the date the document was created, and keywords to describe the document. Metadata for a music file might include the artist's name, the album, and the year it was released.

For computer files, metadata can be stored within the file itself or elsewhere, like is the case with some EPUB book files that keep metadata in an associated ANNOT file.

Metadata represents behind-the-scenes information that's used everywhere, by every industry, in multiple ways. It's ubiquitous in information systems, social media, websites, software, music services, and online retailing. Metadata can be created manually to pick and choose what's included, but it can also be generated automatically based on the data.

Types of Metadata

Metadata comes in several types and is used for a variety of broad purposes that can be roughly categorized as a business, technical, or operational.

• Descriptive metadata properties include title, subject, genre, author, and creation date, for example.
• Rights metadata might include copyright status, rights holder, or license terms.
• Technical metadata properties include file types, size, creation date and time, and type of compression. Technical metadata is often used for digital object management and interoperability.
• Preservation metadata is used in navigation. Example preservation metadata properties include an item's place in a hierarchy or sequence.
• Markup languages include metadata used for navigation and interoperability. Properties might include heading, name, date, list, and paragraph.

Metadata and Website Searches

The metadata embedded in websites is critically important to the success of the site. It includes a description of the website, keywords, metatags, and more — all of which play a role in search results.

Some common metadata terms used when building a web page include meta title and meta description. The meta title briefly explains the topic of the page to help readers understand what they'll get from the page should they open it. The meta description is further information, though brief, about the contents of the page.

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Both of these metadata pieces are displayed on search engines for readers to get a quick glimpse of what the page is about. The search engine uses this information to group together similar items so that when you search for a specific keyword or group of keywords, the results are relevant to your search.

A web page's metadata might also include the language the page was written in, like whether it's an HTML page.

Metadata for Tracking

Retailers and online shopping sites use metadata to track consumers' habits and movements. Digital marketers follow your every click and purchase, storing information about you such as the type of device you use, your location, the time of day, and any other data they're legally allowed to gather.

Armed with this information, they create a picture of your daily routine and interactions, your preferences, your associations, and your habits, and can use that picture to market their products to you.

Internet service providers, governments, and anyone else with access to large collections of metadata information could potentially use the metadata from web pages, emails, and other places there are users online, to monitor web activity.

Since metadata is a short representation of the larger data, this information could be searched through and filtered to find information about millions of users at once and track things like hate speech, threats, etc. Some governments have been known to collect this data, including not only web traffic but also phone calls, location information, and more.

Metadata in Computer Files

Every file you save on your computer includes some basic information about the file so that the operating system understands how to deal with it, and so that you or someone else can quickly gather from the metadata what the file is.

For example, in Windows, when you view the properties of a file, you can clearly see the file's name, the file type, where it's stored, when it was created and last modified, how much space it's taking up on the hard drive, who owns the file, and more.

The information can be used by the operating system as well as other programs. For instance, you might use a file search utility to quickly find all the files on your computer that were created sometime today and that is bigger than 3 MB.

Metadata in Social Media

Every time you friend someone on Facebook, listen to music Spotify recommends for you, post a status or share someone's tweet, metadata is at work in the background. Pinterest users can create boards of related articles because of metadata stored with those articles.

Metadata is useful in very specific social media situations such as when you're looking for someone on Facebook. You can see a profile image and a short description of the Facebook user to learn just the basics about them before deciding to friend them or send them a message

Metadata and Database Management

Metadata in the world of database management might address the size and formatting or other characteristics of a data item. It's essential to interpreting the contents of database data. The eXtensible Markup Language (XML) is one markup language that defines data objects using a metadata format.

For example, if you have a set of data with dates and names spread all about, you can't know what the data is representing or what the columns and rows are describing. With basic metadata like column names, you can quickly glance at the database and understand what a particular set of data is describing.

If there's a list of names without metadata to describe them, they could be anything, but when you add metadata to the top that says "Employee's Let Go," you now know that those names represent all of the employees who have been fired. The date beside them can also be understood as something useful like "Termination Date" or "Hire Date."

What Metadata Isn't

Metadata is data that describes data, but it isn't the data itself. The author and creation date metadata stored in a Microsoft Word document, for example, is not the entirety of the document but instead just a few details about the file.

Since metadata is not the actual data, it can usually safely be made public because it doesn't give anyone access to the raw data. Knowing summary details about a web page or video file, for example, is enough to understand what the file is but not enough to actually see the whole page or play the whole video.

Think of metadata as a card file in your childhood library that contains information about a book; metadata isn't the book itself. You can learn a lot about a book by examining its card file, but you have to open the book to read it.