DXF is the most common file format for laser cutting and CNC work, but "DXF" covers two different encodings: ASCII (plain text) and binary. Many laser and CAM programs, and many shops, expect ASCII DXF, and some upload forms refuse binary DXF outright. Here is how to tell which one you have, and how to export an ASCII DXF from the programs customers use most. If a menu name differs slightly in your version, look for the same option in the export or save dialog.
Open the file in a plain text editor (Notepad, TextEdit in plain text mode, VS Code). An ASCII DXF is readable text made of short code/value lines such as 0, SECTION, 2, HEADER. A binary DXF starts with the words AutoCAD Binary DXF followed by unreadable characters. On macOS or Linux, head -c 18 file.dxf prints AutoCAD Binary DXF for a binary file.
Use Save As (or the SAVEAS command) and pick a DXF file type, for example AutoCAD 2013 DXF or AutoCAD R12/LT2 DXF. Before saving, open Tools > Options in the save dialog, go to the DXF Options tab and select ASCII rather than Binary. The same tab lets you set the decimal places of accuracy; a lower value such as 6 to 8 is plenty for cutting and gives a smaller file.
In Autodesk Fusion (Fusion 360), right-click the sketch in the browser and choose Save As DXF. For sheet metal parts, create the flat pattern first and use the DXF export from the flat pattern's right-click menu. Export only the profile you want cut: hide or delete construction lines and dimensions first, then run the text editor check from step 1 on the result.
Convert text and shapes to paths first (Path > Object to Path), because the DXF export works on paths. Then use File > Save a Copy and choose Desktop Cutting Plotter (AutoCAD DXF R14) (*.dxf), or the R12 variant if your shop asks for R12. Set the base unit to millimetres or inches in the export options so the part keeps its real size. Inkscape writes these DXF files as plain text.
In LibreCAD, use File > Save As and choose a DXF type in the file type list (for example DXF 2007 or DXF R12). QCAD works the same way. These free CAD programs save DXF as text, and they are a practical way to open a problem file and save a clean copy.
Use File > Export > Export As and choose AutoCAD Interchange File (DXF). In the DXF/DWG export options, choose an AutoCAD version your shop can read, set the scale and units to 1:1 in millimetres or inches, and outline text if the option is offered. Then run the text editor check from step 1.
Older versions are read by more programs. R12 is the most compatible, but it predates some entity types: splines and lightweight polylines may be converted or approximated when you save to R12. Versions from about 2000 to 2013 keep those entities and are read by most current laser software. If the shop states a version, use that one.
ASCII files are larger than binary ones, so remove what the machine does not need: dimensions, title blocks, hatches, hidden layers and construction lines. Lower the decimal precision where your program allows it, and simplify splines or traced outlines that contain thousands of tiny segments.
AutoCAD Binary DXFIf you sell laser or CNC work on Shopify and customers upload their own files, CutReady checks the file on the product page before add-to-cart. It accepts only .dxf, .svg and .pdf, with size limits of 256 KB for SVG, 512 KB for ASCII DXF (binary DXF is not accepted) and 2 MiB for PDF, and add to cart stays locked until the file passes ("File OK"). Free trial, then 39 USD every 30 days, billed by Shopify. The app is awaiting Shopify App Store review.