What is the BK2 file format?
A .bk2 file is a Bink Video 2 file, a proprietary game video format developed by RAD Game Tools (acquired by Epic Games in 2021). Bink 2 was introduced in 2013 as a next-generation replacement for the original .bik Bink 1 format, offering significantly better compression and image quality at comparable bitrates.
The file opens with the three-byte signature KB2 at offset 0; the fourth byte is a revision letter identifying the codec variant (KB2a through the current KB2i). Revisions KB2a-KB2f used a floating-point DCT encoder; KB2g onward switched to 16-bit integer DCT, which decodes faster on modern CPUs and game hardware. A little-endian uint32 at bytes 4-7 stores total file size minus the first 8 bytes. Audio is encoded by the Bink/Miles Sound System codec and supports mono, stereo, or multi-track streams - multi-track is commonly used to bundle multiple dubbed language versions of a cutscene.
Bink 2 is extensively used for in-game cutscenes in AAA titles across Windows, PlayStation 4/5, Xbox One/Series, Nintendo Switch, iOS, and Android. Since Epic acquired RAD Game Tools in 2021, Bink 2 is deeply integrated into Unreal Engine. Files can be played with RAD Video Tools, VLC media player (with codec support), MPC-HC, or mpv; an up-to-date FFmpeg build is recommended for newer KB2i files.
Security & safety
RISK: LOW.bk2 files are video data, not executable, and playing them in VLC or RAD Video Tools is safe. Avoid 'BK2 codec pack' or 'BK2 player' download sites - these are common adware/PUP vectors. Use only VLC (videolan.org), official RAD Video Tools (radgametools.com), or FFmpeg (ffmpeg.org).
Format details
in a nutshellPrograms that open BK2 files
Windows3 apps
VLC media player
Open-source Current VLC (via FFmpeg backend) plays most .bk2 files. Open directly; no codec pack needed. Some very recent KB2i files may need a VLC/FFmpeg update. 
RAD Video Tools (Bink)
Free Open the .bk2 to play; use 'Convert a file' to export to AVI/MP4. The authoritative Bink 2 player - RAD's own free toolkit.
MPC-HC
Open-source Media Player Classic with LAV filters (FFmpeg) plays .bk2; a lightweight alternative to VLC. 
macOS2 apps
Linux2 apps
FFmpeg / mpv
Open-source 'mpv file.bk2' to play or 'ffmpeg -i file.bk2 out.mp4' to convert. Ensure FFmpeg is up-to-date for newer KB2i files. Technical details
deep spec| Encoding | Binary |
| Byte order | Little-endian |
| Magic bytes | 'KB2' (0x4B 0x42 0x32) at offset 0; byte 3 is the codec revision letter (a-i) |
| File size field | Bytes 4-7 store total file size minus the first 8 bytes (little-endian uint32) |
| Codec revisions | KB2a-KB2f used floating-point DCT; KB2g-KB2i (current) use 16-bit integer DCT for faster decoding |
| Container structure | Header with frame dimensions/rate/count/audio info, per-frame offset table, interleaved video and audio packets |
| Audio codec | Bink/Miles Sound System; supports mono, stereo, or multi-track streams (e.g., multiple language dubs) |
| Audio sample rates | 44.1 kHz or 48 kHz |
| Color format | YUV (typically 8-bit per channel); optional alpha plane for overlay compositing |
| Resolution support | 320×240 up to 4096×2160 (4K); practical ceiling is game/SDK-dependent |
| Typical file size | 5 MB - 500 MB (AAA game cutscenes; console titles often larger) |
| Platform support | Windows, macOS, Linux, PlayStation 4/5, Xbox One/Series, Nintendo Switch, iOS, Android |
| Checksum/integrity | None (per-frame offset table used for seeking; no whole-file checksum) |
| Distinction from Bink 1 | Bink 1 files (.bik) use BIK signature; Bink 2 is a separate codec with improved compression and quality |
| Released | 2013 (Bink Video 2, RAD Game Tools) |
| Latest version | KB2i (16-bit integer DCT encoding; used in current titles) |
| Specification | www.radgametools.com |
BK2 conversions
Community Q&A
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