Click Here to Install Silverlight*
United StatesChange|All Microsoft Sites
Microsoft
How to Tell 
|How to Tell Worldwide|Windows Comparison Guide|Office Comparison Guide
What is a Certificate of Authenticity (COA)?

A Certificate of Authenticity (COA) is a label that helps you identify genuine Microsoft software. A COA is not a software license – it is a visual identifier that assists in determining whether or not the Microsoft software you are running is genuine. However, without it, you will not have a legal license to run Microsoft software. A COA should never be purchased by itself without the software it authenticates.

To help you verify the authenticity of the Microsoft software you acquired, be sure that your software came with one of the following COAs (or a previous version) and that the COA includes the advanced piracy prevention features described.

Retail Software COAs
Retail Software COAs
Enlarge | View Previous Versions

For software that is purchased separately from a computer through retail channels, the COA will be affixed to the top of the software packaging.

More Information
Large Manufacturer Pre-installed Windows COAs
Large Manufacturer Pre-installed Windows COAs
Enlarge | View Previous Versions

For Windows software that comes pre-installed by a large manufacturer (also known as an Original Equipment Manufacturer or OEM) on a computer, the COA should be affixed to the body of the computer. The COA includes the 25-character product key, which would be required if a reinstallation is needed.

More Information
Small Manufacturer Pre-installed Windows COAs
Small Manufacturer Pre-installed Windows COAs
Enlarge | View Previous Versions

For Windows software that comes pre-installed by a small manufacturer (also known as a System Builder) on a computer, the COA is typically affixed to the body of the computer. The COA includes the 25-character product key, which would be required if a reinstallation is needed. Some System Builders include the Windows software with new computers but do not pre-install it. These computers should come with Pre-installed Windows COAs.

More Information
Pre-installed Non-Windows Software COAs
Pre-installed Non-Windows Software COAs
Enlarge | View Previous Versions

For non-Windows software (Microsoft Office for example) that comes with the purchase of a computer, the COA should be included with your system recovery disc or Office Ready PC packaging.

More Information
Refurbished PC Pre-installed Windows COAs
Refurbished PC Pre-installed Windows COAs
Enlarge

Microsoft Authorized Refurbishers that pre-install Windows XP Home Edition for Refurbished PCs or Windows XP Professional for Refurbished PCs attach a COA to the body of the computer. The COA features the Microsoft product name printed near the top of the label and a 25-character product key, which would be required if a reinstallation is needed.

More Information
Embedded Windows COAs
Embedded Windows COAs
Enlarge

For Windows software that comes pre-installed on PDAs and other small devices, the COA may be affixed to the body or under the battery. Printed on the label are the product name and serial number.

More Information
Don't fall victim to stand-alone COAs

If you receive offers for COAs as stand-alone items, be aware that these offers are highly suspect and can put you at risk. To fall victim to stand-alone COAs offers means that you may have wasted valuable money and you will not have a legal license to run the software. The best way for you to protect yourself is to purchase software from a familiar, reputable reseller. The Anti-Counterfeiting Act of 2003 makes it a criminal offense for dishonest resellers to distribute stand-alone COA labels.

Search How to Tell
Genuine Microsoft Software
Genuine Microsoft Software

Be confident that your software is legitimate and fully supported by Microsoft. Learn more about the benefits of genuine Microsoft software

Report Suspected Piracy
Report Suspected Piracy

Think you may have received counterfeit software? Want to report suspected piracy?


© 2008 Microsoft Corporation. All rights reserved. Contact Us |Terms of Use |Trademarks |Privacy Statement