What is the KWZ file format?
A .kwz file holds a flipnote, the flipbook-style animation you make in Flipnote Studio 3D. Nintendo released the app for the Nintendo 3DS in Japan on July 24, 2013, and later in North America and Europe. Each file stores a run of hand-drawn frames, and every frame has three drawing layers taken from a small fixed palette of colors. Because the 3DS screen is stereoscopic, each layer also carries a depth value, so a flipnote can play back in 3D. Sound rides along as up to four tracks of a custom ADPCM audio codec.
Inside, a .kwz is a series of tagged sections: a header, an 80x64 thumbnail, the compressed frame images, a per-frame metadata table, and the audio. The last 256 bytes are an RSA-2048 signature over the whole file, which the console checks before it will load a flipnote. The name comes from *kawazu*, an old Japanese word for frog. The format is the successor to the DSi-era .ppm flipnote.
Security & safety
RISK: LOWA .kwz is a passive animation data file with no scripting or executable code, so opening one cannot run a program. Every genuine flipnote is RSA-signed, and an unmodified 3DS rejects files that fail the signature check. The main caveat is that files from unofficial sources may not validate on real hardware, but they pose no security risk to a computer.
Format details
in a nutshellFULL NAMEFlipnote Studio 3D Animationaka Flipnote Studio 3D flipnote, KWZ flipnote
DEVELOPERNintendo (Nintendo EAD Tokyo)since 2013
CATEGORYVideo Files
MIME TYPEapplication/octet-stream
TYPEBinary animation container with proprietary video, audio and thumbnail codecs
This extension is also used by…
- Kindle Word Wise data - Some converter sites list .kwz alongside Kindle Word Wise, but this is not an established standalone file type.
MAGIC BYTES · FILE SIGNATURE
OFFSET
000102
HEX
4B4648
ASCII
KFH
There is no single fixed whole-file signature. A KWZ is a run of 8-byte-headed sections whose 4-character tags start with a capital K (KFH file header, KTN thumbnail, KMC frame data, KMI frame metadata, KSN sound). A normal flipnote opens with the KFH section, so the first three bytes are usually 'KFH', but folder-icon and comment variants of the format start with other sections.
Programs that open KWZ files
Windows1 app
kwz-parser (Python)
Open-source Run this reference Python parser from the command line to decode a .kwz file's frames and audio for inspection or conversion. 
macOS1 app
kwz-parser (Python)
Open-source Run this reference Python parser from a terminal to decode a .kwz file's frames and audio. 
Linux1 app
kwz-parser (Python)
Open-source Run this reference Python parser from a terminal to decode a .kwz file's frames and audio.
Web3 apps
Flipnote Player (flipnote.rakujira.jp)
Open-source Drag a .kwz file onto the page to play it in the browser and export it as MP4, GIF, or an image sequence.
flipnote.js
Open-source Use this JavaScript library to parse and play .kwz (and .ppm) files in a web page or Node.js, with built-in GIF and WAV output.
Sudomemo Flipnote Archive
Free Browse and play archived flipnotes online; the site renders KWZ animations without needing the original app. Technical details
deep spec| Encoding | Binary, little-endian |
| Byte order | Little-endian |
| Container | Section-based container. Each section has an 8-byte header: a 4-character tag (the first three bytes name the section, the fourth carries flags) plus a 32-bit little-endian size, followed by the section body. |
| Sections | KFH (file header and metadata), KTN (thumbnail), KMC (compressed frame/layer data), KMI (per-frame metadata table), KSN (audio tracks). |
| Compression | Proprietary tile-based lossless video compression. Each layer is split into 8x8-pixel tiles grouped into 128x128 blocks, using I-frame and P-frame encoding with several tile types (uniform, alternating-pattern, per-line index, skip-unchanged). |
| Resolution | 320x240 pixels canvas |
| Layers | 3 drawing layers (A, B, C) per frame, each with a 3D depth value of 0-6 for stereoscopic rendering |
| Color Palette | Per-layer palette drawn from white, black, red, yellow, green and blue, plus transparent paper |
| Frame rate | Configurable playback speed, roughly 0.2 to 30 FPS |
| Audio Codec | Mono IMA ADPCM at 16364 Hz with a custom step-index clamp and diff range; up to four tracks (background music plus sound effects) |
| Thumbnail | KTN section stores an 80x64 JPEG preview |
| Integrity | KFH header carries a CRC32; the final 256 bytes of the file are an SHA-256 / RSA-2048 digital signature computed over the whole file, used by the console to verify authenticity. |
| Encryption | Not encrypted, but signed. The RSA signature prevents tampered flipnotes from validating on an unmodified 3DS. |
| Typical size | A few hundred KB to a few MB depending on frame count and audio |
| Structure | Header + thumbnail + frame image data + frame metadata + audio, followed by a trailing RSA-2048 signature. |
| Platforms | Nintendo 3DS |
| Notes | The name KWZ comes from kawazu (かわず), an archaic Japanese word for frog. On a 3DS SD card the files live in region-specific folders (JKZJ Japan, JKZE North America, JKZP Europe). A KWZ is the successor to the DSi-era PPM flipnote format. |
| Released | 2013 |
| Latest version | Flipnote Studio 3D (final app build) |
| Specification | github.com |
KWZ conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about KWZ files.
Frequently asked questions
How do I open a KWZ file on a computer?
Use the web-based Flipnote Player at flipnote.rakujira.jp. Drag the
.kwz file onto the page and it plays in the browser, with buttons to export GIF, MP4, or images. No install is needed.What program originally made KWZ files?
Flipnote Studio 3D, a free animation app Nintendo released for the Nintendo 3DS. The app has been removed from download, which is why fan-made viewers are now the common way to open these files.
Can I convert a KWZ to MP4 or GIF?
Yes. Flipnote Player and the flipnote.js library both export a
.kwz to animated GIF and to MP4 video with the original audio. On the 3DS itself the app could also save GIF and AVI.Why won't my KWZ file play on my 3DS?
Every flipnote is signed with an RSA-2048 signature over the whole file. If a file was edited or created outside the app, the signature no longer matches and an unmodified 3DS refuses to load it.
What is the difference between KWZ and PPM?
PPM is the older flipnote format from Flipnote Studio on the DSi. KWZ is its 3DS successor, adding a third drawing layer, stereoscopic 3D depth, and richer audio. The tools that read one usually read the other.
Is a KWZ file safe to open?
Yes. It is plain animation data with no executable code, so it cannot run anything on your device. Opening it in a viewer just decodes the frames and audio.
References
1Wikipedia: Flipnote Studio 3Den.wikipedia.org
2Flipnote-Collective KWZ Format wiki (community spec)github.com
