DXF files

Which conversion do you need?

• DXF to PDF to share, print or archive a drawing: A4, A3, Letter or the drawing's own size, fitted to the page or at 1:1.
• DXF to SVG for laser cutters, websites and illustration apps, at real-world scale, with a hairline option.

The converter above does both. Pick the format under Conversion before you add your files.

What a DXF file is

DXF, short for Drawing Exchange Format, arrived with the first release of AutoCAD in 1982. AutoCAD's own DWG format wasn't documented, so Autodesk described DXF in the open as the way to move drawings in and out of other programs, and it still publishes a reference for each version.

Inside, a DXF is plain text: a long list of numbered pairs, where a group code says what the value after it means. The file is split into sections. The header holds settings such as units and the version, the tables hold layers, line types and text styles, the blocks section holds reusable parts, and the entities section holds the drawing itself: lines, arcs, circles, polylines, splines, text, hatches and dimensions.

Because the format is documented, nearly every CAD, CAM and GIS program reads or writes it. DXF files come from AutoCAD and AutoCAD LT, BricsCAD, DraftSight, LibreCAD and QCAD; from FreeCAD, SolidWorks and Fusion as 2D exports and sheet-metal flat patterns; from OpenSCAD, KiCad board outlines and QGIS map exports; and from vector apps like Inkscape and Illustrator. Laser and CNC shops often ask for DXF because their nesting software reads it.

DXF versions

A DXF names the AutoCAD release it was saved for in its header, as a code in $ACADVER:

• AC1009 Release 11 and 12
• AC1012 Release 13
• AC1014 Release 14
• AC1015 AutoCAD 2000
• AC1018 AutoCAD 2004
• AC1021 AutoCAD 2007
• AC1024 AutoCAD 2010
• AC1027 AutoCAD 2013
• AC1032 AutoCAD 2018

Each version added entity types and settings, but the pairs-and-sections structure has stayed the same. Our test drawings cover every format from AutoCAD 2000 to AutoCAD 2018, plus minimal files with no header at all, the bare form OpenSCAD writes. Every one of them in ASCII form converts.

Text encoding changed in 2007. From AC1021 on, text is UTF-8. Older files name a code page in the header, such as ANSI_1252 for Western European languages or ANSI_932 for Japanese, and we decode the text with it. Characters written as \U+ codes are decoded too.

ASCII DXF, binary DXF and DWG

DXF comes in two forms. ASCII DXF is the text version described above, and it's what nearly every program writes. Binary DXF stores the same pairs in a compact binary form. AutoCAD writes it when you ask for it, and we can't read it yet; you'll get a clear message if you drop one.

To save ASCII DXF from AutoCAD, choose Save As and pick one of the DXF file types. In the same dialog, Tools › Options › DXF Options switches between ASCII and binary, and ASCII is the default. Other CAD apps usually write ASCII whenever you export DXF.

DWG is AutoCAD's native format. Autodesk has never published its specification, and reading it reliably is a large project of its own, so we haven't taken it on yet. Any app that opens a DWG can save a DXF copy, and that copy converts here. If you drop a DWG anyway, we count the request, the file extension and nothing else, which helps us decide what to build next.

What we draw

We draw the model space, where a drawing is made, usually at full size. Layouts (paper space), where viewports, title blocks and sheet notes are arranged for printing, are left out, and What changed counts the entities skipped.

As a CAD print would, we skip layers that are frozen, turned off or set not to plot, along with the Defpoints layer. Blocks are expanded wherever they're inserted, nested blocks and arrays included, and dimensions are drawn from the geometry saved with each one. External references (XREFs) live in other files, so they aren't loaded; bind them into the drawing in your CAD app first.

Units come from the drawing's header ($INSUNITS): inches, feet, millimetres, centimetres or metres. A drawing with no units, or a unit we don't handle, is treated as millimetres, and What changed says so.

How we test

The tables on the PDF and SVG pages come from running the real converter on 53 licensed test drawings, taken from the test suites of two open-source DXF projects. 52 of them convert to both PDF and SVG. The one that doesn't is a binary DXF, refused with the message below, and 3 have nothing in model space to draw.

For the 49 drawings with something to compare, we count every entity we draw or approximate and check it against an independent open-source DXF reader: 2,748 of 2,755 in total. Every drawing reaches at least 98.2%, above our 95% line, except 3 with known reasons. In one, the reference reader counts a circle inside a stretched block as an ellipse, while we draw the stretched circle and count it as a circle. One has a dimension saved without its geometry, and one holds an embedded OLE object, which we don't draw.

Dimensions with saved geometry: 55 of 55 drawn. On a core set of 20 drawings we also check where things land. 565 of 565 pieces of text sit within 2% of the drawing's width of where the reference reader puts them. Everything else we draw spans the same area as in the reader, each edge within 0.5% of the drawing's width, in 18 drawings. In the other 2, one edge differs because the reader carries a spline past its end; the other edges match.

These counts are a check on placement and completeness, not a pixel-by-pixel comparison of the drawing. Our tests run all of them again on every change to the code, and they fail if a number moves.

When a DXF won't convert

The file's row tells you when something stops a conversion. Here's what each message means and what to do.

• "This format isn't on our list yet" The file isn't a .dxf. Most often it's a DWG; save a DXF copy from your CAD app and drop that instead.
• "This is a binary DXF. Save it as ASCII DXF in your CAD app, then try again." The drawing was saved in binary form. Save it again as ASCII DXF, as described above.
• "This file looks damaged, or it isn't the format its name suggests." The file has no DXF sections in it. It may be a DWG renamed to .dxf, or a download or email attachment that didn't arrive in full. Export it again from the original app.
• "This drawing has more detail than we can draw on this device. Simplifying it, or splitting it into smaller drawings in your CAD app, can help." Every drawn item, curve point and block copy counts toward a budget of 20,000,000, which stops the conversion before the tab runs out of memory. Drawings packed with circles and arrays reach it sooner than their size suggests; about 270,000 circles is enough. Frozen layers are skipped before anything is drawn, so freezing the layers you don't need helps. PDF and SVG draw the same thing, so switching formats won't.
• "This file is on the large side" Files over 50 MB ask before they start, and you can always continue. On our test machine, a recent Apple computer, a 50 MB synthetic drawing converted in about 2.5 to 4 seconds, and the tab used up to about 2 GB of memory. Phones and older computers have less memory to spare; if the whole tab crashes, it ran out. Closing other tabs gives it more room. Files over 1 GB stop with "This file is too large to convert on this device. A smaller file or more memory may help."
• "Something unexpected stopped this conversion. If trying again doesn't help, reload the page." Reload the page and convert the file once more. If the same file keeps failing, save it again from your CAD app and try the new copy.