What is the DLM file format?
A .dlm file is an incomplete, in-progress download staging file created by Akamai Download Manager (ADM), a client application developed by Akamai Technologies for distributing large software packages over the internet. Adobe was its most prominent adopter, using ADM to deliver Creative Suite installers from roughly 2003 until the transition to Creative Cloud around 2012-2013.
Internally, a .dlm file contains the raw bytes of the target file received so far - its content mirrors whatever the destination format is (installer, ISO, archive, etc.) rather than following a fixed .dlm-specific structure. No consistent magic header identifies it. Download state data - byte ranges, target URL, and resume pointers - is stored in a companion sidecar file or in ADM's internal database, not inside the .dlm itself.
Microsoft File Transfer Manager, used for MSDN and TechNet downloads, also produced .dlm partial download files - a separate, unrelated product that happened to share the same extension. 3ds Max also uses .dlm in a completely different context (for modified DLL files).
Both Akamai Download Manager and Microsoft File Transfer Manager are discontinued. .dlm files found today are typically orphaned fragments that can no longer be resumed. They are functionally similar to .part files created by Firefox and other modern download managers - the safest approach is to delete them and restart the download with current tools.
Security & safety
RISK: LOWA .dlm file is incomplete downloaded data - it cannot execute. Risk level matches the original downloaded content: if it was an installer for legitimate software, no concern; if the source is unknown, treat with usual suspicion. Do not attempt to rename and run partial executable downloads.
Format details
in a nutshell- Microsoft File Transfer Manager Partial Download - Microsoft used .dlm for partial downloads via its File Transfer Manager (MSDN/TechNet downloads), also discontinued.
- 3ds Max DLL Module (modified) - Some 3ds Max (.max) plugin deployments rename modified DLL files to .dlm; entirely unrelated to downloads.
Programs that open DLM files
Windows1 app
(No current software can resume .dlm files)
Free Akamai Download Manager is discontinued and can no longer resume these files. Delete the .dlm and re-download from the vendor's current site (e.g., adobe.com for Creative Cloud). If the .dlm is a partial of a known file type, rename and attempt to open - success only if the download was effectively complete. Technical details
deep spec| Developer | Akamai Technologies (ADM); also Microsoft (File Transfer Manager) |
| File content | Raw bytes of the in-progress download target (no fixed internal structure) |
| Magic bytes | None fixed - mirrors the target file's own header bytes |
| Encoding | Binary |
| Typical size | 0 bytes - several GB (scales with download progress and target file size) |
| Metadata storage | Companion sidecar file or downloader's internal database (not embedded in .dlm) |
| Associated OS | Windows, macOS |
| Primary deployment | Adobe Creative Suite distribution via Akamai CDN (~2003-2013) |
| Also used by | Microsoft File Transfer Manager (MSDN/TechNet downloads); 3ds Max (unrelated: modified DLL files) |
| Status | EOL - Akamai Download Manager discontinued; files cannot be resumed with current software |
| Released | Early 2000s (Akamai Download Manager client used for large software distribution) |
DLM conversions
Community Q&A
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