What is the MET file format?
.met files are binary metadata and index files used internally by eMule and its cross-platform counterpart aMule to persist application state between sessions. Several named variants exist, each serving a different purpose within the P2P client.
The main variants are:
server.met- the ED2K server list (version byte0x0Eat offset 0)known.met- index of all downloaded and shared files, including ED2K/MD4 hashes (version byte0xE1)clients.met- the known peer listpart.met- per-file download state with block availability maps for incomplete downloads
All variants use a tag-value binary encoding in little-endian byte order. The known.met and part.met files store ED2K/MD4 hash values as integrity identifiers for each file entry. File sizes range from under 1 KB to several MB depending on the size of the local library.
These files are managed automatically by the eMule client and should not be manually edited or deleted. Deleting server.met resets the server list; deleting known.met causes eMule to forget its entire share and download history; deleting a part.met makes the corresponding partial download permanently unrecoverable.
eMule was first released on May 13, 2002 (version 0.01a) and remains actively maintained as of version 0.60d (2022). The .met format also connects to the .emulecollection format for grouped file sets.
Security & safety
RISK: LOWMET files are passive binary indexes with no executable code. No security risk from the files themselves. Deleting a part.met permanently loses the associated partial download.
Format details
in a nutshell- OmniPage Pro Document - Nuance OmniPage (OCR software) used .met for a proprietary document format in older versions.
- Windows Metafile (WMF-related) - Some older Microsoft tools used .met for Windows metafile-related data; distinct from WMF.
Programs that open MET files
Windows2 apps
eMule
Open-source MET files are opened and managed automatically by eMule at startup. Do not open manually. 
aMule
Open-source MET files are read/written automatically by aMule. Compatible with eMule's MET format. 
macOS1 app
aMule
Open-source aMule on macOS manages MET files automatically in ~/Library/Application Support/aMule/. 
Linux1 app
Technical details
deep spec| Encoding | Binary, little-endian |
| Magic byte - server.met | 0x0E at offset 0 |
| Magic byte - known.met / clients.met | 0xE1 at offset 0 |
| Data encoding scheme | Tag-value binary pairs |
| Integrity check | ED2K/MD4 hash per file entry (in known.met and part.met) |
| Typical size range | 1 KB - 5 MB (server.met ~50 KB; known.met grows with shared library size) |
| Variants | server.met, known.met, clients.met, part.met |
| Platform support | Windows, Linux, macOS |
| First release | eMule 0.01a, May 13, 2002 |
| Latest eMule version | 0.60d (2022) |
| Deletion risk | Deleting part.met makes the corresponding partial download permanently unrecoverable |
| Management | Auto-managed by client - not intended for manual editing or deletion |
| Associated file types | .part (incomplete download) and .emulecollection (grouped file set) |
| Session persistence | Read on startup and written on shutdown to preserve eMule client state between sessions |
| Released | 2002 (eMule 0.01a, May 13, 2002) |
| Latest version | eMule 0.60d (2022) |
| Specification | wiki.amule.org |
MET conversions
Community Q&A
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