What is the SAI file format?
Files stored with the .sai extension are images originating from the PaintTool SAI program - a lightweight painting application for Windows developed by SYSTEMAX Software Development. .sai files contain all graphic projects created within the software, including layer data, blend settings and canvas metadata, stored in a proprietary encrypted container.
PaintTool SAI is a program dedicated mainly to digital artists and illustrators. It is not designed for photo processing; its task is to create drawn and painted graphics. Users have at their disposal a wide range of brushes and tools, including both raster and vector linework layers. The interface is clean and responsive, which has made PaintTool SAI a popular lightweight alternative to heavier editors that use formats such as .clip.
Additional information about .sai files:
.saifiles support multiple separate layers, including raster painting layers and vector linework layers..saifiles can be exported as standard raster images such as .png, or as .psd compatible with Photoshop and other editors..saigraphic files are proprietary; because the format is not publicly documented, opening or editing them in other applications requires exporting to a compatible format first.- PaintTool SAI ver.2 saves projects with the
.sai2extension, which is a distinct and incompatible format from.sai.
Security & safety
RISK: LOWA .sai is passive image data - it contains no executable code, so the artwork itself is safe. The realistic cautions are non-malware: because only PaintTool SAI opens the format, never delete your .sai originals before you've exported a backup (PSD), and keep .sai files if you might re-edit (PNG/JPG exports lose your layers). Shared SAI files are someone's original art - respect the artist's rights. Beware fake 'SAI file viewer/opener' download sites that bundle adware; the real software is PaintTool SAI from systemax.jp.
Format details
in a nutshellPrograms that open SAI files
Windows2 apps
PaintTool SAI
Paid The only practical opener - File > Open the .sai to view and fully edit all layers. Inexpensive; free 31-day trial; SAI Ver.2 (technical preview) opens .sai too. 
libsai (developer tool)
Open-source For developers only: decrypts and dumps a .sai's internal structure/layers. Not a viewer or editor - use it to extract data, not to open artwork normally. Technical details
deep spec| Developer | SYSTEMAX Software Development |
| Platform | Windows only |
| Container structure | Proprietary encrypted filesystem-like container holding canvas data, layers, layer thumbnails and metadata |
| Layer types | Raster painting layers, vector linework layers, and layer groups |
| Layer blending modes | Multiply, Screen, Overlay, Luminosity, and several others |
| Per-layer alpha | Full alpha transparency supported on each layer |
| Color mode | RGB, 8 bits per channel |
| Canvas size limit | Up to 10,000 × 10,000 pixels (SAI v1) |
| MIME type | application/octet-stream |
| File identification | No public magic bytes; identified by the .sai extension and PaintTool SAI file origin |
| Encryption | Lightly encrypted proprietary encoding with no published decryption specification |
| Open-source parsing | Format partially reverse-engineered by the libsai open-source project |
| Successor format | .sai2, used by PaintTool SAI ver.2 - a distinct and incompatible format |
| Export options | PNG, BMP, JPEG and PSD available via PaintTool SAI's built-in export |
| Layer count | No fixed hard limit; bounded by available system memory |
| Released | PaintTool SAI v1 public release 2008 (Japan); SYSTEMAX, Tokyo |
| Specification | www.systemax.jp |
SAI conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about SAI files.
