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SOLIDWORKS File Extensions

SOLIDWORKS uses several file formats for storing 3D parts, assemblies, drawings, templates, and design data. Understanding these file extensions is important when creating, editing, sharing, or converting CAD models.

SOLIDWORKS also supports several neutral CAD formats, which are useful when exchanging models with users of other CAD software.

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SOLIDWORKS File Extensions

The most important SOLIDWORKS file extensions are:

File Extension	File Type	Common Use
.SLDPRT	SOLIDWORKS Part	3D individual parts
.SLDASM	SOLIDWORKS Assembly	Assemblies containing multiple components
.SLDDRW	SOLIDWORKS Drawing	2D manufacturing/engineering drawings
.SLDPS	SOLIDWORKS Part Sheet	Part-related design data
.DRWDOT	Drawing Template	Drawing templates
.PRTDOT	Part Template	Part templates
.ASMDOT	Assembly Template	Assembly templates
.SLDBLK	Block	Reusable 2D drawing blocks

The three primary SOLIDWORKS formats you should remember are:

SLDPRT → Part

SLDASM → Assembly

SLDDRW → Drawing

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1. .SLDPRT — SOLIDWORKS Part

The SLDPRT file is the native SOLIDWORKS format for individual parts.

It can contain:

• 3D solid geometry
• Sketches
• Features
• Dimensions
• Configurations
• Materials
• Design history
• Custom properties

Example

A mechanical component such as a:

Bracket → Bracket.SLDPRT

can be used as a component inside an assembly.

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2. .SLDASM — SOLIDWORKS Assembly

The SLDASM format is used for assemblies.

An assembly can contain multiple:

• Parts
• Subassemblies
• Components
• Mates

Example

A pump assembly could contain:

Pump Housing.SLDPRT

Impeller.SLDPRT

Shaft.SLDPRT

Bearing.SLDPRT

These components can be combined into:

Pump.SLDASM

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3. .SLDDRW — SOLIDWORKS Drawing

The SLDDRW format is used for 2D engineering drawings.

A drawing can contain:

• Orthographic views
• Section views
• Detail views
• Dimensions
• Annotations
• GD&T
• Bill of Materials
• Balloons
• Title blocks

Example

A 3D component:

Bracket.SLDPRT

can have a corresponding drawing:

Bracket.SLDDRW

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4. .PRTDOT — Part Template

A PRTDOT file is a template used when creating new SOLIDWORKS parts.

A company template may contain predefined:

• Units
• Materials
• Document properties
• Drafting standards
• Custom properties

Example

Company_Part_Template.PRTDOT

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5. .ASMDOT — Assembly Template

An ASMDOT file is an assembly template.

It can contain predefined document settings for new assemblies.

Example

Company_Assembly_Template.ASMDOT

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6. .DRWDOT — Drawing Template

A DRWDOT file is used as a template for creating new drawings.

It can contain:

• Sheet size
• Title block
• Drawing standard
• Units
• Annotation settings
• Document properties

Example

A3_Drawing_Template.DRWDOT

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Common Neutral CAD Formats

Neutral CAD formats allow geometry to be transferred between different CAD systems.

This is particularly useful when the sender and receiver use different software.

Extension	Format	Common Use
.STEP / .STP	STEP	3D CAD data exchange
.IGES / .IGS	IGES	CAD geometry exchange
.SAT	ACIS	Solid-model exchange
.X_T	Parasolid	High-quality solid/surface exchange
.X_B	Parasolid Binary	Parasolid exchange
.STL	Stereolithography	3D printing/mesh
.3MF	3D Manufacturing Format	3D printing
.OBJ	Wavefront OBJ	Mesh/3D geometry

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1. STEP — .STEP / .STP

STEP is one of the most commonly used neutral CAD formats.

It is widely used for transferring:

• Solid geometry
• Surface geometry
• Assemblies
• Product manufacturing information, depending on the STEP application protocol

Best For

CAD-to-CAD data exchange

For example:

SOLIDWORKS → STEP → Another CAD Software

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2. IGES — .IGES / .IGS

IGES is an older neutral CAD exchange format.

It can transfer:

• Curves
• Surfaces
• Wireframe geometry
• Some solid-related data

It is still encountered in older CAD workflows, although STEP is often preferred for modern solid-model exchange.

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3. Parasolid — .X_T / .X_B

Parasolid is a geometric modeling kernel used by SOLIDWORKS and various other CAD systems.

Common file formats include:

.X_T — Parasolid text

.X_B — Parasolid binary

These formats can provide excellent transfer of solid and surface geometry between compatible CAD systems.

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4. STL — .STL

STL represents a 3D object using a triangular mesh.

It is commonly used for:

• 3D printing
• Rapid prototyping
• 3D scanning
• Mesh-based applications

Important

STL generally does not contain the original parametric CAD history.

For example, it does not normally preserve:

Sketch → Extrude → Fillet → Chamfer

as editable SOLIDWORKS features.

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5. SAT — .SAT

SAT is associated with the ACIS geometric modeling system.

It can be used to exchange:

• Solids
• Surfaces
• 3D geometry

It may be useful when exchanging geometry with software based on ACIS.

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6. OBJ — .OBJ

OBJ is a mesh format commonly used for:

• 3D visualization
• Rendering
• Scanning
• Animation
• Mesh processing

It is generally less appropriate than STEP or Parasolid for transferring editable mechanical CAD solids.

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7. 3MF — .3MF

3MF is a modern format developed for additive manufacturing and 3D printing workflows.

It can store more manufacturing-related information than traditional STL workflows.

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Native vs Neutral CAD Formats

Feature	Native SOLIDWORKS	Neutral CAD
Example	SLDPRT	STEP
Native feature history	✅	Usually ❌
Sketches	✅	Usually not preserved as editable features
Parametric features	✅	Usually ❌
CAD exchange	Limited to compatible software	Excellent
Best for	SOLIDWORKS design	Cross-CAD exchange

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Which Format Should You Use?

For SOLIDWORKS Parts

Use:

.SLDPRT

For SOLIDWORKS Assemblies

Use:

.SLDASM

For SOLIDWORKS Drawings

Use:

.SLDDRW

For Sharing 3D CAD With Other CAD Software

Use:

.STEP / .STP

or, when appropriate:

.X_T / .X_B

For 3D Printing

Use:

.STL

or:

.3MF

For Older CAD Exchange

Use:

.IGES / .IGS

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Frequently Asked Questions (FAQs)

1. What is the SOLIDWORKS part file extension?

The primary SOLIDWORKS part extension is:

.SLDPRT

2. What is the SOLIDWORKS assembly extension?

The assembly file extension is:

.SLDASM

3. What is the SOLIDWORKS drawing extension?

The drawing extension is:

.SLDDRW

4. What is the best neutral CAD format?

For many modern CAD exchange workflows, STEP is an excellent general-purpose choice. Parasolid can also provide very good solid/surface transfer when the receiving system supports it.

5. Does STEP preserve SOLIDWORKS feature history?

Generally, no. STEP primarily transfers geometry and associated supported product data rather than the original SOLIDWORKS feature tree.

6. Is STL the same as SLDPRT?

No.

STL = mesh

SLDPRT = native SOLIDWORKS parametric part

An STL can be imported into SOLIDWORKS, but it does not normally contain the original feature history.

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Conclusion

Understanding SOLIDWORKS file extensions makes CAD data management and file exchange much easier.

Most Important Extensions

• SLDPRT → SOLIDWORKS Part
• SLDASM → SOLIDWORKS Assembly
• SLDDRW → SOLIDWORKS Drawing
• PRTDOT → Part Template
• ASMDOT → Assembly Template
• DRWDOT → Drawing Template

Common Neutral Formats

• STEP → General CAD exchange
• IGES → Curves and surface exchange
• X_T / X_B → Parasolid solid/surface exchange
• STL → 3D printing and mesh data
• 3MF → Modern 3D printing

For professional mechanical CAD exchange, SLDPRT/SLDASM are ideal when working within SOLIDWORKS, while STEP and Parasolid are commonly useful when exchanging models between different CAD platforms.

SOLIDWORKS Visualize Help: Supported Import & Export Formats: Official Dassault Systèmes documentation listing compatible 3D solid, mesh, neutral (STEP, IGES, Parasolid), and native CAD file types.

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