What is the ACSM file format?
A .acsm file contains XML-based data for activating and downloading an e-book - for example, titles purchased through Adobe Content Server and opened in Adobe Digital Editions software. ACSM files don't contain actual e-book data, but only the information that allows users to legally download, authorize, and open a given e-book. The file's XML root element is <fulfillmentToken>, declared in the http://ns.adobe.com/adept namespace, making it a plain text document rather than binary data. An .acsm file can also contain an expiration date after which the content can no longer be downloaded. Software that uses .acsm files relies on Adobe's proprietary ADEPT (Adobe Digital Experience Protection Technology) DRM system.
Opening an .acsm file and downloading the e-book it references is possible with any application that supports the ADEPT fulfillment process, or with apps using the Adobe Reader Mobile SDK on mobile devices. The delivered file is typically a DRM-protected EPUB or PDF. An .acsm file is typically shipped alongside an e-book purchased through a digital bookstore. The primary application for .acsm files is Adobe Digital Editions (ADE), available on Windows, macOS, iOS, and Android. A conceptually similar but open alternative is the .lcpl token used by the Readium LCP DRM standard.
Security & safety
RISK: LOWAn ACSM is plain XML - it cannot carry executable code and is safe to open. Practical risks are different: 'free ACSM converter' websites are scams or DRM-circumvention tools of dubious legality, and an expired token (typically store-dependent) simply stops working - re-download from your store/library account. Keep your Adobe ID credentials safe; books are locked to it.
Format details
in a nutshellPrograms that open ACSM files
Windows1 app
Adobe Digital Editions
Free Install ADE (4.5.12), authorize with a free Adobe ID (Help → Authorize Computer), then double-click the .acsm - ADE downloads the actual EPUB/PDF into your library. 
macOS1 app
Adobe Digital Editions
Free Install, authorize with an Adobe ID, open the .acsm to fulfill the book. 
Android2 apps
Adobe Digital Editions (Android)
Free Open the downloaded .acsm with the ADE app after authorizing with your Adobe ID.
PocketBook Reader
Free Supports Adobe DRM: link your Adobe ID in settings, then open the .acsm to download the book - popular ADE alternative.
Adobe Digital Editions (iOS)
Free Open the .acsm from Files/Safari with 'Open in Digital Editions'; sign in with the same Adobe ID as on desktop. Technical details
deep spec| File type | XML text document (UTF-8); not a binary format |
| MIME type | application/vnd.adobe.adept+xml |
| XML root element | <fulfillmentToken> in the http://ns.adobe.com/adept namespace |
| DRM system | Adobe ADEPT (Adobe Digital Experience Protection Technology) |
| Purpose | Fulfillment token / download ticket - instructs ADE to retrieve the actual e-book from Adobe Content Server |
| Delivered content format | DRM-protected EPUB or PDF (the actual e-book, separate from the .acsm token) |
| Typical file size | Under 1 KB - contains only authentication and download metadata |
| Binary signature | None - identified by XML content and root element, not a fixed byte-offset magic number |
| Primary application | Adobe Digital Editions (ADE) - Windows, macOS, iOS, Android |
| Content server | Adobe Content Server (ACS) - fulfills the token and delivers the protected e-book |
| Expiry support | Token may carry an expiration date; after expiry it cannot be used to download |
| Network requirement | Active internet connection required at fulfillment time to contact Adobe Content Server |
| Third-party support | Limited; PocketBook Reader (Android) supports ADEPT fulfillment; most readers do not |
| Open alternative | Readium LCP DRM uses an .lcpl token - a conceptually similar but open-standard approach |
| Released | 2008 (Adobe Content Server 4 / Adobe Digital Editions ADEPT DRM) |
| Specification | www.adobe.com |
ACSM conversions
Community Q&A
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