What Is a Product Key?

How they're formatted and why you might need to find yours

The product key is a usually unique, alphanumeric code of any length required by many software programs during installation. They help software developers ensure that each copy of their software was legally purchased.

Most software, including some operating systems and programs from most popular software makers, require product keys. As a general rule these days, if you pay for a program, then it probably requires a product key during install.

A laser reading a bar code
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In addition to product keys, some software makers, including Microsoft, often require product activation to help further ensure that software is obtained legally.

Open source and free software programs usually don't require a product key unless the manufacturer implements its use for statistical purposes.

Product keys are also sometimes called CD keys, key codes, licenses, software keys, product codes, or installation keys.

How Product Keys Are Used

A product key is like a password for a program. This password is given upon buying the software and can only be used with that specific application. Without the product key, the program will most likely not open past the product key page, or it might run but only as a trial of the full version.

Product keys can usually only be used by one installation of the program but some product key servers allow for the same key to be used by any number of people so long as they're not used simultaneously.

In these circumstances, there's a limited number of product key slots, so if the program using the key is shut down, another can be opened and use that same slot.

Microsoft Product Keys

All Microsoft Windows operating system versions require the entry of unique product keys during the installation process, as do all versions of Microsoft Office and most other Microsoft retail programs.

Microsoft product keys are often located on a product key sticker. In most versions of Windows and other Microsoft software, product keys are 25-characters in length and contain both letters and numbers.

In all versions of Windows since Windows 98, including Windows 10, Windows 8, Windows 7, Windows Vista, and Windows XP, product keys are of the five-by-five set (25-character) form as in xxxxx-xxxxx-xxxxx-xxxxx-xxxxx.

Older versions of Windows, like Windows NT and Windows 95, had 20-character product keys that took the form of xxxxx-xxx-xxxxxxx-xxxxx.

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