Official versions are available on the Google Play Store and the iOS App Store, often published by MobiSystems.
Oxford University Press is a business. The 13th edition retails for approximately £35–£45 ($45–$55 USD). OUP does not release official free PDFs of current editions. Any website offering a direct "free download" of the 13th edition is almost certainly: Concise Oxford English Dictionary 13th Edition Free Download
: Downloading pirated software or books violates intellectual property laws. How to Access Oxford Dictionaries for Free (Legally) Official versions are available on the Google Play
: If you are looking for free, legally downloadable older versions, the Internet Archive hosts several public domain editions of the Concise Oxford Dictionary of Current English Quick Facts: 12th Edition (Current) : August 2011. : Over 240,000 words, phrases, and definitions. legally downloadable older versions