BK2 File

What are BK2 files and how to open them

Are you having problems opening a BK2 file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your BK2 files.

What is a BK2 file?

A .BK2 file is a BizHawk Movie Capture file.

BizHawk movie capture files store a complete record of gameplay inputs, emulator settings needed for deterministic replay, and optional metadata such as subtitles, comments, and savestate anchors. They are used by the BizHawk emulator for tool-assisted speedruns (TAS) and rerecording workflows, allowing a session to be paused, branched, edited frame-by-frame, and replayed with precise timing and sync.

The BizHawk emulator creates these files during its "Movie Record" operations (including via its TAStudio tool). After recording, users may replay them, edit them (e.g. inputs or branches), or export the playthrough to video formats separately. BizHawk uses the movie file to ensure that every frame of input with the correct emulator core, firmware, and synchronization settings produces the same gameplay result.

These files are ZIP archives containing several internal files, all encoded in UTF-8 (text) or structured formats:

• A header file (Header.txt) listing metadata fields such as author, GameName, platform, emulator version, hash of the ROM, core used, and whether the recording started from a savestate. ", showing which buttons are pressed and analog values when applicable.
• A SyncSettings file (SyncSettings.json) specifying emulator core settings required for reproducible playback. - Optional files like Subtitles.txt, Comments.txt, and a CoreState-anchored savestate when recording starts from one.

Byte signatures include the ASCII characters "PK" at the start (indicating a ZIP container) and the presence of internal filenames like "SYNCSETTINGS.JSON", "INPUT LOG.TXT", "SUBTITLES.TXT", "COMMENTS.TXT", and "HEADER.TXT".

How to open BK2 files

Important: Different programs may use files with the BK2 file extension for different purposes, so unless you are sure which format your BK2 file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested ten different BK2 openers which you will find listed below.

Last updated: August 24, 2026

Various apps that use files with this extension

These apps are known to open certain types of BK2 files. Remember, different programs may use BK2 files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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