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Open STEP & STP Files Online

Open STEP and STP files in your browser. No CAD install and no account. Measure edges and holes, and read volume from a closed solid.

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Capabilities and limits

  • Open STEP and STP files in the browser with no CAD install and no account. Measure edges and holes, and read volume when the model is a closed solid.
  • Closed-solid properties and supported B-Rep measurements are separate from approximate point-to-point picks on the display mesh.
  • Files are uploaded for server processing; support depends on format, version and geometry.
  • Viewing and measuring do not require an account. Sign in to convert, save files across devices or create share links.
On this page

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Open a STEP or STP file in the browser and view it. No install and no account.

To view a STEP file, upload it: select or drop the .step or .stp file in the viewer and the model opens in 3D for rotating, sectioning and measuring.

Open a STEP or STP file

  1. Open the viewer and select or drop a .step or .stp file.
  2. Wait while the file is processed on the server. Viewing and measuring need no account, and guest files are temporary.
  3. Read the Properties panel first: the solid count, the X × Y × Z extents and any geometry warning. Compare one extent with a dimension you already know.
  4. For an assembly, open Structure and check that every expected component is listed.

Then check dimensions or closed-solid volume, or convert STEP to STL. If the part is still a SolidWorks file, export SolidWorks to STEP and open that file here.

A shaded view can hide a missing body or an open surface. Edge length, hole diameter and volume use supported B-Rep. Volume is shown only for a valid closed solid and is never reported as zero when it is unavailable. A point picked on the shaded view is approximate.

If you are not sure what the file contains, what a STEP file is and how to open it explains the file header, the AP203, AP214 and AP242 names, and what a STEP file can and cannot carry.

Inspect an assembly part by part

Select a component, then control visibility — assembly.step (STEP)
assembly.step: the Model structure panel lists Twin blocks with Block 1 and Block 2, and offers Multi-select, Hide selected, Isolate, Show all and a part search.

Self-contained STEP assemblies keep readable component names, colors and placements. Use the Model structure panel to select a component, hide it, isolate it or find a part by name. Totals count repeated instances, and overlapping parts are not subtracted. Hiding, clipping or exploding a part changes only what you see, not the source geometry.

Choose the right measurement mode

Measurement modes: distance, edge, angle, hole or circle, surface area and solid volume — assembly.step (STEP)
assembly.step in Measure: distance, edge, angle, hole or circle, surface area and solid volume, with a length unit selector.

The modes answer different questions, so keep the mode and unit next to every number you copy out.

  • Distance between two picked points is approximate, because the pick lands on the display mesh.
  • Edge length and Hole / circle diameter read supported B-Rep geometry. Click a circular edge or a cylindrical wall to read a diameter; a cylinder can be an outer surface rather than a hole.
  • Hole type and depth are shown for simple cases: full cylindrical through holes and flat-bottom blind holes. Stepped, intersecting and conical-bottom holes remain unclassified.
  • Surface area and Solid volume come from the B-Rep when the file provides a valid closed solid. When it does not, the result is unavailable and is never shown as zero. Source units, method and precision in the Properties panel states how each value was obtained.

Section and display the model

Section with a single cutting plane — assembly.step (STEP)
assembly.step with a single section plane and its handles; the panel offers Reverse side, Hide cutting plane and Reset section.

Section cuts the view with a single plane, several planes or a box, and you can reverse the side or hide the cutting plane. It clips only what you see; it does not calculate a cross-section area. The display options include wireframe and transparent views, which help when one body hides another.

Checks specific to STEP files

  • Units. Compare one known dimension before using any measurement. A model that is 25.4 times too large or small points to an inch and millimetre mix-up; see fixing a 25.4 scale error.
  • External references. CADProps reads self-contained STEP files and does not fetch files an assembly refers to. If parts are missing, ask the sender for a single-file assembly export.
  • Open surfaces. A model that looks solid can be a set of open surfaces. Volume is then unavailable; why STEP volume is zero or missing explains the cause.
  • Feature history. A STEP file carries the resulting geometry, not the feature tree. See why STEP export has no feature tree.
  • Protocol. The header names the application protocol the exporter used. AP203, AP214 and AP242 lists what each can carry.

STEP file will not open or the viewer is blank

  • Wrong extension or content. Renaming another CAD file to .step does not convert it. A real STEP file is text and starts with ISO-10303-21;. Open it in a text editor to check; if it begins differently, ask for a fresh export.
  • Truncated download or email. A file that ends without END-ISO-10303-21; was cut off. Download or export it again.
  • Blank canvas but properties are listed. Check the extents in Properties. A very small or very large model can look empty at the default zoom; compare the extents with a known size and rule out the inch/millimetre mix-up in fixing a 25.4 scale error.
  • Missing parts in an assembly. The file may reference other files that were not included. Ask for a single-file assembly export.
  • Only surfaces or nothing shaded. Some exports contain open surfaces or curves only; see why STEP volume is zero or missing.
  • Still failing. Check the supported size and format limits in Input formats and the STEP file basics.

STP vs STEP: is there a difference?

No. .stp and .step are the same ISO 10303-21 format; only the extension differs, a leftover of the older three-letter limit. The viewer accepts both. What can differ is the application protocol inside (AP203, AP214, AP242), covered in STEP vs STP and AP203, AP214 and AP242.

Input formats: STEP / STP

Open this tool

General steps for uploading, viewing, sectioning, measuring, converting and exporting are explained once in How it works. This page covers what is specific to this file type.

Real CADProps screenshots

The screenshots show the English interface. Captions and instructions describe the same operations.

Properties — block.step · 40 × 30 × 20 mm · 24,000 mm³ · 5,200 mm²
Properties — block.step · 40 × 30 × 20 mm · 24,000 mm³ · 5,200 mm²

Sample source and verification

When a result needs another check

Viewing can start without an account. Conversion, account storage and share creation require signing in. Temporary files expire after the displayed retention period. Read the privacy statement for server processing and deletion, and the accuracy notes before using numerical results. Do not assume that hiding a part, clipping it or exploding an assembly changes the exported source geometry.

When a result needs another check · Input formats

Continue with a related task

For fast part and assembly viewing, see Fast CAD viewing with CADProps, with real model examples and loading times.

Original article: CADProps · https://www.cadprops.com/tools/step-viewer/

A reproducible example

Generated STEP block: 40 × 30 × 20 mm, surface area 5,200 mm² and volume 24,000 mm³. At density 2.7 g/cm³ the calculated mass is 64.8 g. These values describe the synthetic block, not the default bearing sample.

Repository-generated samples are synthetic test models. Verify your own model's units and geometry before using results.

Supported formats
All formats and limits →

Questions about this task

How can I inspect repeated part instances in a STEP assembly?

Self-contained STEP assemblies preserve readable names, colors and placements. Totals count repeated instances; overlapping parts are not subtracted.

Can I measure a hole diameter in a STEP file online?

Full cylindrical through holes and flat-bottom blind holes may expose depth. Stepped, intersecting and conical-bottom holes remain unclassified.

Are STEP files uploaded to a server when I view them?

Selecting a file starts temporary server processing. For guests, access to the workspace copy is limited to the browser session; it can be deleted early and expires after the displayed period. Signed-in files are saved to the account library when space is available; otherwise they remain temporary.

How can I open a STEP file on a Mac?

On macOS, open the CADProps STEP Viewer in a WebGL-capable browser, select a .step or .stp file and wait for server processing. Rotate or zoom the model and inspect its dimensions in Properties. Check a known dimension before using measurements; volume requires valid closed solids. Viewing needs no CAD installation or account, but the file is uploaded to the server.

How can I open a STEP file on Linux?

On Linux, use a WebGL-capable browser to open the CADProps STEP Viewer, upload a .step or .stp file and wait until the 3D model appears. You do not need a Windows CAD program or Wine for this browser workflow. Rotate or zoom the model and check its dimensions. If the view is blank, check browser graphics support and processing warnings; file complexity and GPU support can limit viewing. Files are processed on the server.

Related reading

Checks that help with this file.

All guides →
Opening files

STEP File (.step, .stp): What It Is and How to Open It

A STEP file is a neutral ISO 10303 CAD model saved as plain text. See what it contains, how to open a .step or .stp file online, and what to check first.

Read the guide →File formats

STEP vs STP: Same Exchange Format, Different Extension

STEP and STP are two common extensions for the same STEP exchange data, not different formats. Learn what renaming changes, what it does not, and which checks matter more.

Read the guide →Measurement

Measure STEP Files Online: Dimensions, Distances & Units

Measure STEP files online, check X/Y/Z dimensions, verify units, distinguish bounding boxes from local measurements, and record the geometry scope correctly.

Read the guide →Measurement

STEP File Bounding Box: Get Overall Dimensions Online

Read a STEP file's overall X, Y and Z extents, understand why orientation changes a bounding box, and avoid confusing envelope dimensions with drawing dimensions.

Read the guide →Measurement

How to Calculate Volume from a STEP File

Calculate volume from a STEP file using valid CAD solid geometry, verify units and body scope, diagnose unavailable results, and use volume safely for mass estimates.

Read the guide →Measurement

Calculate Surface Area from a STEP File

Calculate STEP file surface area from CAD faces, verify units and body scope, distinguish total geometry from process area, and avoid common coating-estimate mistakes.

Read the guide →