STL ASCII ↔ Binary Converter
Upload an STL file, auto-detect ASCII or Binary format, convert to the other format and compare file sizes. Fully browser-local.
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About This Tool
STL files come in two formats: ASCII (human-readable text) and Binary (compact). This tool detects the current format and converts to the opposite. Binary STL is typically smaller and faster to load; ASCII is easier to debug.
Tips
- 1Format is auto-detected on upload
- 2Binary STL is usually 4–5× smaller than ASCII
- 3Geometry is preserved — only encoding changes
- 4Preview your model in the 3D viewer before downloading
How to Use
Upload STL
Drop or browse for your .stl file
Review Detection
See detected format and file size in the sidebar
Convert
Toggle target format if needed — conversion runs automatically
Download
Download the converted STL and compare sizes
Frequently Asked Questions
What's the difference between ASCII and Binary STL?
ASCII STL stores triangles as readable text; Binary STL stores them as compact binary data. Both represent the same geometry. Binary files are typically much smaller.
Will conversion change my model geometry?
No. Only the file encoding changes. Triangle data is preserved through load and re-export.
Which format should I use for 3D printing?
Both work with most slicers. Binary STL is preferred for large files due to smaller size and faster loading.
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