Convert STL ASCII to Binary (and back)
Convert a text (ASCII) STL into the compact binary STL that slicers load faster, or the other way round for inspection. Binary files are typically 4–5× smaller.
How it works
- 1Drop the STL
The encoding is detected automatically.
- 2Check the sizes
The tool shows the current encoding and the size after conversion.
- 3Download
The output is the opposite encoding with identical triangles.
Details
An STL file can be text (ASCII) or binary. ASCII STL starts with the word "solid" and lists every vertex as readable numbers, which makes it roughly five times larger than binary. Binary STL has an 80-byte header, a 4-byte triangle count and 50 bytes per triangle.
Some CAD exports and older tools produce ASCII by default. Slicers read both, but binary loads faster, uploads faster and is the expected format for print services. The reverse conversion is useful when you want to inspect a file or debug a mesh in a text editor.
Accepted formats: STL
Frequently asked questions
More STL tools
- Get the Dimensions of an STL File
Drop an STL (or any 3D file) to read its exact width, depth and height, bounding box, volume, surface area and triangle count. Runs in your browser, nothing is uploaded.
- Reduce STL File Size (Simplify Mesh)
Cut the triangle count of an STL file by a chosen percentage while keeping the shape. Useful for oversized 3D scans, slow slicers and upload limits. Runs locally in your browser.
- Scale / Resize an STL File
Resize a 3D model by a factor, to an exact target dimension, or fix a model that came out 25.4× too small or too big because of inch/millimeter confusion.
- Repair an STL File
Weld duplicate vertices, remove degenerate triangles, recompute normals and get a report of open and non-manifold edges before you slice. Basic repair for common export problems.
- STL File Info: Binary or ASCII, Triangle Count, Header
Inspect what is inside an STL file: encoding, header text, triangle count, bounding box and whether the mesh is closed. Handy before sending a file to a print service.