cadcraft/docs/file-format-parity.md

File-format parity

Last reviewed: 2026-10-10 · Last updated: 2026-10-11 · Change: minor (DXF/DWG saved at a chosen version 2000–2018, binary DXF written, #421) · Target: Autodesk AutoCAD 2027

Every format AutoCAD 2027 reads or writes, with CADCraft's support, fidelity and tests. Work items are in gaps.md; the weighted score feeds target-app-parity.md.

Headline (estimated): file formats ≈ 30% of AutoCAD's. Opening the commonest 2D DXF/DWG drawings works, but saving is lossy: everything CADCraft doesn't model is dropped, and no test uses a real third-party file. DXF and DWG save at 2000–2018 (2018 by default, #421). Remaining: ≈ 170–280 Opus 5.5 hours: ≈ 40–60 h for DXF/DWG fidelity (the part that decides beta), ≈ 110–180 h for the other formats below, and ≈ 20–40 h for 3D exchange formats that wait for 3D modelling.

How this was measured

• CADCraft: read from crates/dxf, crates/io (dxf_read.rs, dxf_write.rs, pdf.rs, svg.rs, tests.rs) and crates/dwg on 2026-10-10. Nothing was run (the measurement pass did no builds).
• AutoCAD: the formats in its Open/Save As/Import/Export/Attach/Plot dialogs, from Autodesk's published documentation and the menu tree in xtask/data/menu-catalog.txt. The installed AutoCAD 2027 for Mac bundle was inspected by listing names only (clean-room rule: nothing inside it is read): Resources/Support lists acad.lin, acadiso.lin, acad.pat, acadiso.pat, acad.mln, .dct spell dictionaries, .pss and .shx files, which confirms the supporting formats below exist in the target. None of them may be copied.
• No AutoCAD-produced file is committed or used as a fixture. A real-file corpus needs owner action (see gaps.md): files made by people who license them to us, kept in a separate storytold/cadcraft-corpus repo.

DWG, version by version

AutoCAD 2027 opens every DWG version from R2.0 onward and saves 2018 (AC1032, still the current DWG format), 2013, 2010, 2007, 2004, 2000 and R14. CADCraft reads DWG by converting it to DXF with the acadrust 0.6.3 crate and reading that DXF; it saves by writing its own R2000 DXF and converting it to a DWG of the chosen version (#421): SAVEAS version, else the drawing's own version (the file's $ACADVER, 2018 for a new drawing), at least 2004 unless 2000 is asked for. The bridge repairs two acadrust 0.6.3 gaps in 2010+ DWG: merged table cells and table-style title/header suppression.

DWG version	Code	AutoCAD 2027	CADCraft read	CADCraft write	Tested how
R1.0–R2.6, R9, R10, R11/R12	MC0.0–AC1009	read	no (is_dwg accepts only AC10xx magic; acadrust doesn't target pre-R13)	no	—
R13	AC1012	read	acadrust claims support; untested	no	none
R14	AC1014	read, write	acadrust claims support; untested	no	none
2000–2002	AC1015	read, write	yes via bridge	yes, when asked for (no true colours, transparency or table styles: the format has none)	synthetic round trips (dwg_at_every_version_reads_back, dwg_roundtrip_keeps_non_ascii_text)
2004–2006	AC1018	read, write	via bridge	yes	dwg_at_every_version_reads_back, dwg_roundtrip_keeps_extension_data
2007–2009	AC1021	read, write	via bridge	yes	dwg_at_every_version_reads_back
2010–2012	AC1024	read, write	via bridge	yes	dwg_at_every_version_reads_back, ac1024_dwg_with_many_entities_opens
2013–2017	AC1027	read, write	via bridge	yes	dwg_at_every_version_reads_back
2018–2027	AC1032	read, write (default)	via bridge; untested on real files	yes (default for new drawings)	dwg_at_every_version_reads_back (synthetic only)
Web build	—	—	no (error: "save as DXF")	no	—

Everything lost in the DXF read/write paths below is also lost through DWG, plus whatever acadrust's own DXF output omits (proxy objects, ACIS data, custom objects: not measured). User report #57: a 10 MB DWG failed after about two minutes; limits now stop runaway conversions early (#175), but the throughput problem remains. DWG ≈ 30% read, ≈ 15% write.

DXF, version by version

DXF version	AutoCAD 2027	CADCraft read	CADCraft write
R12 (AC1009), ASCII	read, write	yes: no version gating; old-style POLYLINE/VERTEX read (polyface meshes flattened to 3D polylines)	no
R12 binary	read, write	no (binary parser expects R13+ 2-byte group codes)	no
R13–R2018, ASCII	read, write each of 2000/2004/2007/2010/2013/2018	yes, one reader for all versions	yes, each of 2000–2018 (#421): R2000 structure (later versions add only optional groups) with that $ACADVER; UTF-8 text from 2007; no CLASS instance counts (91)
R13–R2018, binary	read, write	yes	yes, each of 2000–2018 (SAVEAS binary; a binary file stays binary on QSAVE)
Code pages ($DWGCODEPAGE, ANSI_932/936/949/950/125x)	yes	no: UTF-8, else Latin-1, so pre-2007 CJK and Cyrillic files are garbled	writes \U+ escapes (#169), which is correct
\U+/\M+ escapes	yes	\U+ yes; \M+ not checked	\U+ yes

DXF content: read and write by object type

Content	Read	Write	Notes
LINE, POINT, CIRCLE, ARC, ELLIPSE, LWPOLYLINE (widths, bulges, elevation), SPLINE, RAY, XLINE	yes	yes	round-trip tests
POLYLINE 2D/3D	yes	yes (as LWPOLYLINE / 3D POLYLINE)	polyface and polygon meshes flattened: lossy
TEXT, MTEXT, ATTDEF, INSERT + ATTRIB	yes	yes	ATTDEF prompt kept (#137)
DIMENSION (all 7 kinds)	yes	yes, with anonymous *D blocks	*D blocks duplicate on re-save (known); DIMASSOC objects written
LEADER	yes	yes
MULTILEADER	no (becomes Unknown)	no: our MLeaders are written as LEADER + MTEXT	MULTILEADER is AutoCAD's default leader since 2008
HATCH pattern / solid	yes	yes
HATCH gradient	yes	yes (#162, fixes #80)
SOLID, TRACE, 3DFACE	yes	yes
ACAD_TABLE	yes	yes (entity + block)
VIEWPORT	yes	yes; frozen-layer lists kept (#150)	VP layer colour overrides lost (#99, PR #197)
IMAGE	partial (no IMAGEDEF, so the file path is empty)	dropped
WIPEOUT	yes	yes (#147, fixes #79)
MLINE, REGION, 3DSOLID, BODY, SURFACE, MESH, TOLERANCE, SHAPE, HELIX, UNDERLAY, OLE2FRAME, LIGHT, CAMERA, SECTION, POINTCLOUD, proxy entities	kept as Unknown (raw tags)	dropped on save	the most serious file gap: opening and saving someone's drawing deletes what we don't model
Header variables	all read	36 written	AutoCAD writes about 280
Tables: LAYER (+ transparency, description), LTYPE, STYLE, DIMSTYLE, BLOCK_RECORD	yes	yes
Tables: VPORT, VIEW, UCS, APPID	not read	VPORT one record; VIEW and UCS empty; APPID yes	named views and UCSs lost
Objects: LAYOUT, DICTIONARY, XRECORD, TABLESTYLE, DIMASSOC	yes	yes
Objects: GROUP, MLINESTYLE, MLEADERSTYLE, IMAGEDEF, SCALE, VISUALSTYLE, PLOTSETTINGS, materials, field objects	ignored	not written (ACAD_GROUP empty)	groups lost
Foreign xdata, extension dictionaries, reactors	not kept	—	third-party application data lost
Handles and owners	regenerated	consistent	handles change on every save

DXF ≈ 50% read, ≈ 30% write (estimated; weights: common 2D entities 50%, annotation objects 20%, tables/objects 15%, foreign data preservation 15%).

Other formats

Format	AutoCAD 2027	CADCraft	Hours to parity (est.)
DWT templates	open, save	no (no template support)	3–5
DWS standards	open, save, CHECKSTANDARDS	no	6–10
PDF output (PLOT, EXPORTPDF)	multi-sheet, layers, searchable text, hyperlinks	vector PDF 1.4, one page, lineweights; no font objects (text is strokes), no layers (OCG), no multi-sheet	10–15
PDF import (PDFIMPORT) and PDF underlays (PDFATTACH)	yes	no	15–25
Raster images attach (PNG, JPEG, TIFF, BMP …)	yes	IMAGE entity exists, no attach/loading/display path	6–10
PNG / JPEG / BMP / TIFF export	PNGOUT, JPGOUT, BMPOUT, TIFOUT	PNG; SVG too (AutoCAD doesn't export SVG)	1–2
DWF/DWFx export, DWF underlay	yes	no	10–15
DGN import/export/underlay	yes	no (needs a public spec; owner decision)	25–40
WMF, EPS, ACIS SAT, STL, FBX, IGES/STEP (Windows), 3DS	various	no; most are 3D and wait for M11	20–40
SHX fonts (.shx, big fonts)	read	not parsed: our stroke font or FONTALT stands in, so text metrics differ from AutoCAD	8–12
Linetype (.lin) and hatch pattern (.pat) files	load user files	own built-in library only; user files can't be loaded	3–5
Plot styles (.ctb, .stb), plotter configs (.pc3), .pmp	yes	plot style tables in our own JSON format (plot-styles.md) and kept in the drawing; binary .ctb/.stb not read (no public spec); no .pc3/.pmp	6–10
Scripts (.scr)	SCRIPT	script text through the CLI, MCP and control channel; no SCRIPT command reading a .scr file	1–2
Aliases (.pgp), CUI(x), workspaces	yes	no	6–10
AutoLISP (.lsp, .fas, .vlx), .dll/.arx plug-ins	yes	no	see gaps.md (M12)
Data extraction (.csv, .xls) and data links	yes	no	6–10
eTransmit (.zip packages)	yes	no	4–6

Tests

crates/io/src/tests.rs has 36 tests (round trips of entities, styles, associativity, tables, constraints, non-ASCII text, DWG round trips, hostile input). All inputs are synthetic: inline strings or our own writer's output. No test opens a file made by another program, and no external validator runs in CI (ezdxf's audit was run by hand once, 2026-10-06). The next step is a licensed real-file corpus with an open → save → re-open → compare test per file, and checking our output in AutoCAD black-box.

Revision history

Date	Change	Summary
2026-10-11	minor	DXF (ASCII and binary) and DWG saved at 2000–2018, 2018 by default (#421)
2026-10-10	minor	WIPEOUT and gradients written since #147/#162; other save losses remain (#201, #204, #208, #209, #213, #223)
2026-10-10	major	First file-format parity doc: DWG and DXF version by version, per-object read/write, other formats