Software & Apps File Types 82 82 people found this article helpful What Is an ACSM File? How to open, edit, and convert ACSM files By Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated April 05, 2020 File Types Design Cryptocurrency MS Office Windows Linux Google Drive Apps File Types Backup & Utilities View More Tweet Share Email A file with the .ACSM file extension is an Adobe Content Server Message file. It's used by Adobe Digital Editions to activate and download Adobe DRM protected content. ACSM files are not eBook files in the regular sense; they can't be opened and read like other eBook formats, like an EPUB or PDF. In fact, the ACSM file itself is nothing but information that communicates with Adobe's servers. There isn't an eBook "locked inside" the ACSM file nor is there a way to extract the book from the ACSM file. Instead, ACSM files contain data from the Adobe Content Server that's used to authorize that the book has been legally purchased so that the real eBook file can be downloaded to your computer through the Adobe Digital Editions program, and then read back through the same software on any of your devices. In other words, once your device is properly set up, you can open an ACSM file to register the book to the ID you've configured Adobe Digital Editions with, and then read the book on any device that's running ADE with the same user ID, without having to repurchase it. There's more information on that process below. How to Open ACSM Files Adobe Digital Editions opens ACSM files on Windows, macOS, Android, and iOS devices. When the book is downloaded on one device, the same book can be downloaded to any other device that's using Adobe Digital Editions under that same user ID. You might be asked to install Norton Security Scan or some other unrelated program during the ADE setup. You can opt out of it if you wish. Use the Help > Authorize Computer menu option in Adobe Digital Editions to connect your eBook vendor account to Adobe Digital Editions. This procedure provisions your books your other devices, that they're re-downloadable should your device fail or the book is deleted, and that you don't have to buy the book again for your other devices. Read Adobe DRM-protected data through the account you entered on that authorization screen. You can also authorize the computer without an ID by checking the appropriate box through the Authorize Your Computer screen. How to Convert an ACSM File Since an ACSM file is not an eBook, it can't be converted to another eBook format like PDF, EPUB, etc. The ACSM file is just a simple text file that describes how to download the real eBook, which might, in fact, be a PDF, etc. To find the book that ADE downloaded using the ACSM file, right-click the book in Adobe Digital Editions and choose Show File in Explorer. In Windows, this is most likely in the C:\Users\[username]\Documents\My Digital Editions\ folder. Still Can't Open Your File? Since it's a bit different than other file formats, if you can't open your ACSM file, dive into the errors you see. If an authentication error arises when you open the eBook, chances are that you're not logged in under the same ID that purchased the book or you don't have ADE installed. However, if you've done everything correctly and your file still isn't opening with the suggestions from above, double-check the file extension to make sure it actually reads "ACSM." Some file formats use a file extension that's spelled similar to ACSM but are actually different and therefore require different programs.