Convert ASCII STL to compact binary STL locally - smaller and faster for any slicer. No upload.
Running locally on your device ...
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Your files never left your device
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
Text-based (ASCII) STL is easy to read but unnecessarily large: every number sits there as a character string. Binary STL stores the same triangle shell as a compact byte sequence and is therefore often several times smaller - saving disk space and speeding up loading in the slicer. This tool reads your ASCII STL and writes the same model as binary STL.
The conversion is lossless: every triangle is carried over and the coordinates are stored as 32-bit floating-point numbers, as the binary STL format prescribes. For each triangle the face normal is additionally computed and placed in the record - exactly as CAD programs and slicers expect.
Everything runs entirely locally in the browser - your possibly confidential model never leaves your device. Honestly framed: binary STL stores 32-bit floating point, which for extremely fine models can mean tiny rounding versus very long decimals in the text - for real-world models this is irrelevant. A file that is not valid STL is rejected with a clear message.
| Input formats | STL |
|---|---|
| Output format | STL |
| Batch processing | No |
| Processing | Locally in your browser (JavaScript) |
| File upload | None |
Limitations: Converts ASCII STL to compact binary STL (lossless): every triangle is kept, coordinates are stored as 32-bit floating point and a normal is computed per triangle. Binary is often several times smaller than text. Already-binary STL is accepted too. A file that is not valid STL is rejected with a clear error.
It is often several times smaller than ASCII STL and loads faster in slicers like Cura or PrusaSlicer.
Binary STL stores 32-bit floating point. For extremely fine models this can mean tiny rounding; for real-world models it is irrelevant.
Yes. For each triangle the face normal is computed and written into the binary record.
No, the conversion happens entirely locally in the browser; your model never leaves your device.