The formats at a glance
| Format | Software | Best for | Watch out for |
|---|---|---|---|
| DWG | AutoCAD and most 2D CAD | 2D drawings and simple 3D, everyday exchange | Version: older AutoCAD cannot open newer DWG |
| DXF | Almost any CAD/CAM | Exchange with other software, laser/plasma/CNC | Loses some AutoCAD intelligence |
| RVT | Autodesk Revit | BIM models with drawings and schedules | Cannot be saved back to older Revit versions |
| IFC | Open standard (Revit, ArchiCAD, Tekla…) | Sharing BIM between different software | Exports need care to keep data correct |
| DGN | Bentley MicroStation | DOT, infrastructure and some UK/AU projects | Levels differ from AutoCAD layers |
| STEP / IGES | SolidWorks, Inventor, Creo, CATIA… | 3D parts between mechanical CAD systems | No feature history – geometry only |
| STL / 3MF | 3D printing and scanning | Meshes for printing and scans | Triangles, not editable CAD geometry |
| Any viewer | Review, markups, permit submission | Not editable – needs PDF to CAD conversion |
DWG vs DXF
DWG is AutoCAD's native format: compact and complete, with blocks, layouts, dimensions, xrefs and plot settings. DXF is a published exchange format that almost any CAD or CAM program can read. Use DWG between AutoCAD users and DXF when sending to other software or a CNC machine. When you order drawings, ask for DWG saved to your AutoCAD version – for example 2018 format – so they open without problems.
RVT vs IFC
RVT is Revit's native model file. It contains everything – families, views, sheets, schedules – but only opens in Revit, and only in the same or newer version. IFC (Industry Foundation Classes, ISO 16739) is an open format for exchanging BIM between different software. Use RVT when everyone uses Revit; use IFC to share with ArchiCAD, Tekla or other platforms, and for open BIM requirements on public projects.
STEP, IGES and native mechanical formats
Mechanical CAD systems each have native formats – SLDPRT and SLDASM for SolidWorks, IPT and IAM for Inventor. STEP (ISO 10303) is the most reliable way to move 3D geometry between them; IGES is older and better for surfaces than solids. Neither carries the feature tree, so an imported STEP part is a 'dumb' solid. If you need editable features, ask for native files or a rebuild – see CAD conversion services.
Which files should you ask your drafter for?
- Native files in your software and version (DWG, RVT, DGN, SLDPRT…).
- PDFs of every sheet, matching the native files.
- Exchange formats your consultants need (IFC, DXF, STEP).
- Fonts, plot styles (CTB/STB) and xrefs bound or included, so drawings plot the same on your side.
Not sure what you have or need? Send a sample and we will tell you – see all services.
When in doubt, ask the person who will open the files next – your consultant, fabricator, reviewer or client – which format and version they need. Five minutes of checking saves a round of re-exports later.
Archiving files for the long term
For records that must be readable in twenty years, keep PDF/A copies of drawings and IFC or STEP copies of models alongside the native files. Native formats change with each software release; open formats and PDF/A are designed to last.
DGN and MicroStation projects
Bentley MicroStation and its DGN format are still standard for many departments of transportation in the US, some infrastructure clients in the UK and Australia, and large plant projects. DGN uses levels instead of AutoCAD layers and has its own cell libraries, line styles and fonts. Converting between DWG and DGN is routine, but the mapping of layers to levels, fonts and line styles must follow the client's standard – otherwise the files fail the agency's CAD checks.
Versions matter
Many 'the file won't open' problems are version problems. AutoCAD can save down to older DWG formats; Revit cannot save to older versions at all – a model upgraded to a newer Revit release stays there. SolidWorks and Inventor files also open only in the same or newer release. Before work starts, tell your drafter which version every member of your team and your consultants uses.
| Software | Save to older version? | Workaround |
|---|---|---|
| AutoCAD (DWG) | Yes | Save As an older DWG format |
| Revit (RVT) | No | Work in the oldest version needed; share IFC or DWG exports |
| SolidWorks / Inventor | No | Share STEP or Parasolid; work in the oldest version needed |
| SketchUp (SKP) | Yes, limited | Save As an older SketchUp version |
Formats for renders and 3D viewing
Rendering and visualisation add more formats: FBX and OBJ move meshes and materials between 3D programs; GLB/glTF and USDZ show products and buildings in web viewers and augmented reality; E57 and RCP carry laser scan point clouds. You rarely need to create these yourself, but it helps to know what your renderer or scanning provider means when they ask for them.
A simple file-delivery checklist
For every delivery, ask for: native files in the agreed version, matching PDFs, exchange formats for your consultants, referenced files (xrefs, links, families, fonts), and a short transmittal listing every file and its revision. That list prevents most of the confusion that happens when files move between offices.
