What is the ZTL file format?
.ztl is the native ZTool file format used by ZBrush, the industry-standard 3D digital sculpting application developed by Pixologic (acquired by Maxon Computer in 2021). A ZTool stores a single sculpting object with its complete working state: mesh geometry at multiple subdivision levels, SubTool hierarchy, Polypaint vertex colors, masking data, texture maps, and material assignments.
The format is proprietary and closed - no third-party application can natively read .ztl geometry. Files are binary, little-endian, and can grow to several gigabytes for high-polygon sculpts. ZBrush can open .ztl files from older versions, but older ZBrush releases cannot open files saved by newer versions.
Geometry export to other applications uses GoZ - a live bridge to Maya, Cinema 4D, Modo, and Blender (via plugin) - or manual export to OBJ, FBX, or STL. For saving a complete ZBrush scene including multiple Tools, canvas settings, and lights, the .zpr (ZBrush Project) format is used instead; .ztl is strictly the per-Tool unit.
ZBrush became free for individual users in April 2022 following Maxon's acquisition. The format has evolved continuously since ZBrush 1.0 in 1999, though the internal versioning scheme remains undocumented.
Security & safety
RISK: LOWZTL files contain 3D geometry data only and pose no known execution risk. Download only from reputable 3D asset marketplaces (ArtStation, Gumroad, ZBrushCentral).
Format details
in a nutshell- Zemax OpticStudio Tolerance Lens Data - Zemax (ANSYS Zemax OpticStudio) uses .ztl for optical tolerance data files - entirely unrelated to 3D sculpting.
Programs that open ZTL files
Windows1 app
ZBrush
Free (individuals) / paid (teams/commerc File > Open Tool, or drag the ZTL onto the LightBox panel. 
macOS1 app
ZBrush
Free (individuals) / paid (teams/commerc File > Open Tool, or drag the ZTL onto the LightBox panel. Technical details
deep spec| Format type | Proprietary binary 3D sculpting tool file |
| Byte order | Little-endian |
| Stored data | Mesh geometry, multiple subdivision levels, SubTool hierarchy, Polypaint vertex colors, masks, textures, material assignments |
| Subdivision levels | Multiple levels stored simultaneously for non-destructive sculpting |
| Vertex color | Polypaint per-vertex color data embedded in file |
| Typical file size | 5 MB - 480 MB; multi-GB for dense high-polygon sculpts |
| Forward compatibility | Newer ZBrush opens old `.ztl` files; older ZBrush cannot open newer files |
| Export paths | GoZ bridge (Maya, Cinema 4D, Modo, Blender), OBJ, FBX, STL |
| Scope | Single Tool (sculpt object); full scene saved as `.zpr` (ZBrush Project) |
| Platform | Windows, macOS |
| Released | 1999 (ZBrush 1.0, Pixologic) |
| Latest version | ZBrush 2024 format (backward-compatible; no public versioning scheme) |
| Specification | docs.pixologic.com |
ZTL conversions
Community Q&A
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