What is the SHX file format?
.shx files are used by AutoCAD - Autodesk's environment for designing 2D and 3D projects for engineering purposes. They are known as compiled shape files, because they contain shape definitions compiled from .shp source files created with the same program. Alongside shape definitions, .shx files may also contain compiled font data originally derived from .shp font scripts or PostScript .pfb font files.
Advantages of .shx files
- Within a compiled
.shxpackage, users can store all the shapes and custom symbols used in a project in a compact binary form. This eliminates the need to redefine the same shapes and fonts each time a drawing is opened, reducing file overhead and saving time. .shxfiles are ready to use immediately after compilation with AutoCAD'sCOMPILEcommand. Once a shape is inserted into a.dwgdrawing, its scale, rotation, and location can be freely adjusted.- AutoCAD processes
.shxfiles much faster than plain.shpsource scripts, because they are a pre-compiled binary representation of the shape and glyph data. The source.shpfiles are plain ASCII text; compiling them into.shxremoves the parsing step at load time.
Each .shx file begins with a readable ASCII identifier string - such as AutoCAD-86 shapes 1.0 or AutoCAD-86 unifont 1.0 - followed by the binary-encoded shape and glyph definitions. This header distinguishes AutoCAD .shx files from the unrelated Esri Shapefile spatial index, which also uses the .shx extension but has a completely different binary structure.
Security & safety
RISK: LOWAn AutoCAD .shx is passive compiled data, not executable, so installing one is safe. The practical pitfalls are about usability: a drawing that references missing .shx fonts shows wrong or boxed text until the font is supplied. Beware 'free SHX font' download sites that bundle adware - get CAD fonts from the drawing's author or a trusted CAD source.
Format details
in a nutshellFULL NAMEAutoCAD Compiled Shape/Font File
DEVELOPERAutodesksince AutoCAD shape/font system, 1980s
CATEGORYCAD Files
MIME TYPEapplication/octet-stream
TYPEBinary compiled shape/font definition (compiled from a .shp shape source) used by AutoCAD to draw symbols and text
This extension is also used by…
- Esri Shapefile Index (.shx) - A GIS spatial index that always travels with a .shp and .dbf of the same name; you open the .shp in QGIS/ArcGIS, not the .shx - completely unrelated to AutoCAD shapes.
Programs that open SHX files
Windows3 apps
AutoCAD
Paid Don't open the .shx - copy it into AutoCAD's Fonts/support folder (or the drawing's folder) so AutoCAD finds the referenced shape/font, then reopen the drawing. 
COMPILE command (AutoCAD)
Paid To build an .shx from a .shp shape source, run the COMPILE command in AutoCAD and select the .shp.
BricsCAD / GstarCAD / ZWCAD
Paid AutoCAD-compatible CAD apps also read SHX fonts/shapes - drop the .shx into their fonts/support folder so referenced drawings render. 
macOS1 app
AutoCAD for Mac
Paid Place the .shx in AutoCAD for Mac's support/Fonts path so drawings that reference it render correctly. Technical details
deep spec| Format type | Binary compiled shape and font definitions |
| Developer | Autodesk |
| Source format | Compiled from plain-text .shp shape/font scripts using AutoCAD's COMPILE command |
| File header | ASCII identifier string at offset 0, e.g. "AutoCAD-86 shapes 1.0" or "AutoCAD-86 unifont 1.0" |
| MIME type | application/octet-stream |
| Encoding | Mixed: human-readable ASCII header followed by binary-encoded vector shape and glyph data |
| Sub-types | Shape files (symbols and special characters) and font files (full glyph sets for text rendering in drawings) |
| Compilation command | COMPILE command in AutoCAD converts a .shp source file into a compiled .shx binary |
| Load command | LOAD command registers shape .shx files; STYLE command references font .shx files in a drawing session |
| Unicode and big-font support | Unifont and big-font .shx variants extend the base format to support multi-byte and Unicode character sets |
| Performance benefit | Pre-compiled binary eliminates parsing overhead at draw time; significantly faster to load than the equivalent .shp source |
| Font rendering speed | SHX fonts render faster than TrueType fonts in AutoCAD and are preferred for large technical drawings with heavy text |
| CAD compatibility | Supported by AutoCAD, BricsCAD, ZWCAD, GstarCAD, and most DWG-compatible CAD applications |
| Name collision | Esri Shapefile spatial indexes also use .shx but begin with big-endian integer 9994 (0x0000270A) - an entirely unrelated GIS format |
| Released | AutoCAD shape/font system, 1980s |
| Specification | help.autodesk.com |
SHX conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about SHX files.
Frequently asked questions
What is a .shx file?
In AutoCAD it's a compiled shape/font file - a binary definition of symbols and font glyphs that AutoCAD uses to draw custom text styles and shapes. It's a resource referenced by drawings, not a file you open directly.
AutoCAD says 'One or more SHX files are missing' - what do I do?
The drawing references a custom shape/font file you don't have. Obtain the named .shx from the drawing's author, place it in AutoCAD's Fonts/support folder, then reopen - or substitute another font when prompted.
How do I install an SHX font?
Copy the .shx into AutoCAD's Fonts folder (or add its folder to the support file search path in Options), then restart or reopen the drawing so the text renders correctly.
How do I create an .shx file?
Write or edit an AutoCAD shape source (.shp text file), then run the COMPILE command in AutoCAD and select it to produce the .shx.
I get 'filename.shx is a normal text font file, not a shape file' - why?
You're feeding AutoCAD an Esri GIS index .shx, which is a different format that just shares the extension. Use that file in GIS software (QGIS/ArcGIS), not AutoCAD.
Can I convert an SHX font to a TrueType (.ttf) font?
Not reliably - an SHX font is a compiled shape definition, not an outline font. A few niche tools attempt it imperfectly; it's better to keep using the .shx inside AutoCAD.
References
1Autodesk - 'One or more SHX files are missing' (AutoCAD)www.autodesk.com
2Autodesk - COMPILE command (build .shx from .shp shape source)help.autodesk.com
