BONK File

What are BONK files and how to open them

Are you having problems opening a BONK 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 BONK files.

What is a BONK file?

A .BONK file is a Bonk Compressed Audio file.

Bonk Compressed Audio is an audio file format used for storing sound using both lossless and lossy compression. It was developed for the Bonk program (accessible via its official page on logarithmic.net), which encodes and decodes audio by compressing it into a single file. The format is designed to reduce file size significantly while preserving perceived sound quality.

In lossy mode Bonk achieves compression ratios around 14:1, yielding bitrates near 95 kilobits per second for stereo audio, while sounding almost perceptually lossless. Lossless mode allows full recovery of the original uncompressed data, typically achieving about 2:1 compression. Bonk works with any sampling rate and supports both music and speech audio.

The encoder breaks the audio into short fixed-length blocks. For each block it builds a linear predictor (using a lattice filter to ensure stability when quantized), applies it to "whiten" the audio block, quantizes the whitened signal (throwing away low-order bits), and stores the predictor plus the quantized signal. In stereo audio it offers mid‐/side encoding as an option rather than storing left and right channels separately. Encoder options include predictor size (default 128), downsampling ratios, and quantization level.

Files in this format begin with the ASCII header ".BONK" (bytes 0x00424F4E4B at offset 0).

How to open BONK files

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

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 24, 2026

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