What is the KFN file format?
.kfn is the proprietary karaoke song container used by KaraFun Player and KaraFun Studio, developed by Recisio (France). Each file bundles everything needed for synchronized karaoke playback into a single binary package: an audio track (typically OGG or MP3), lyrics with timing data, and optional background images.
The container begins with the four-byte ASCII signature KFNB at offset zero, followed by a series of named header fields using four-character names, a flag byte, and then a value or length-prefixed string. The header closes with an ENDH marker, after which embedded files - including a Song.ini metadata and lyrics file and the audio track - are stored sequentially without compression.
Some .kfn files distributed through KaraFun Studio are locked: their Song.ini is encrypted with AES-128 in ECB mode, with the decryption key stored inside the file itself. This makes the protection closer to obfuscation than true DRM; open-source decryptors are available on GitHub.
KaraFun Player also plays CDG and LRC karaoke formats alongside .kfn. Typical file sizes range from 1 MB to 15 MB. KaraFun operates on two content models: downloaded .kfn files for offline playback and a subscription-based streaming library accessed through the same application on Windows, macOS, Android, and iOS.
Security & safety
RISK: LOWKFN files are multimedia containers from a legitimate commercial vendor (Recisio/karafun.com). No known malware uses the .kfn extension. The 'locked' AES encryption in some files is obfuscation (key is inside the file), not a security mechanism. Open-source decryptors are available on GitHub.
Format details
in a nutshellPrograms that open KFN files
Windows2 apps
Karafun Player
Freemium Download KaraFun Player (free). Open KFN files from File > Open or double-click; playback requires a KaraFun account for streamed songs but locally-downloaded KFN files play offline.
KaraFun Studio
Paid KaraFun Studio opens and edits KFN files; can export to video (MP4) for use outside KaraFun. 
macOS1 app
Android1 app
KaraFun Karaoke
Freemium Install from Google Play; open KFN files or stream from the KaraFun catalogue. Technical details
deep spec| Magic bytes | 4B 46 4E 42 ("KFNB") at offset 0 |
| Byte order | Little-endian |
| Container structure | Custom binary header (KFNB…ENDH) followed by sequentially stored embedded files |
| Header field encoding | 4-character field name + flag byte (0x01 = 4-byte uint32; 0x02 = length-prefixed string) |
| Embedded audio | OGG Vorbis or MP3, typically at 44,100 Hz |
| Lyrics and timing file | Song.ini - INI-style metadata and synchronized timing data |
| Embedded image assets | Optional JPEG or PNG background images stored inside the container |
| Compression | None - all embedded files stored uncompressed inside the container |
| Encryption | Optional AES-128 ECB on Song.ini in locked Studio files; decryption key stored within the KFN file itself |
| Typical file size | 1 MB - 15 MB |
| Platform support | Windows, macOS, Android, iOS (KaraFun Player) |
| MIME type | application/octet-stream (no registered MIME type) |
| Additional formats supported by player | CDG, KAR, LRC, KOK, MP3+CDG, MIDI |
| Released | 2004 (KaraFun 1.x) |
| Latest version | KaraFun format as of KaraFun Player 2.15.3 (April 27, 2026) |
| Specification | www.ulduzsoft.com |
KFN conversions
Community Q&A
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