STLBenchFree online STP viewer
STP viewer — and yes, it is just a STEP file
Drop a .stp and it opens here, with no CAD licence and nothing uploaded. The short extension is the only thing that distinguishes it from a .step: the contents are ordinary ISO 10303 text, the two are interchangeable, and a program that accepts one and rejects the other is matching on the filename rather than reading it. The part arrives with its exact surfaces rebuilt, its declared unit stated, and its assembly components placed where the file says they belong.
- 100% free
- No signup
- Same as .step
- No CAD licence
- Nothing uploaded
Drag a file anywhere on this page to open it. F fits the view, W switches shading, G the grid, R spins it.
How to open a .stp file
Three steps, the first of which is not renaming anything.
Drop the .stp
Nothing about the short extension changes how the file is read, and a .step renamed to .stp behaves identically. If your file arrived from a Windows CAD package it is almost certainly spelled this way and there is nothing further to think about.
Confirm what it actually is
The panel names the schema the file declares — AP203, AP214 or AP242 — along with the application that wrote it, where the header says. That is worth a glance when a supplier sends a part you did not expect: the header records which package exported it and when, which is often the fastest way to settle whose revision you are looking at.
Read the part before you accept it
Face count, declared unit, component count, bounding box, surface area and enclosed volume, all from the file's own geometry rather than a mesh someone made of it. If the volume is nowhere near what the material cost implies, you have found a problem before it reached the machine.
Technical specifications
| Extension | .stp — identical contents to .step |
|---|---|
| Origin of the name | The DOS three-character limit, still with us |
| Standard | ISO 10303, AP203 / AP214 / AP242 |
| Read | Exact surfaces, trimmed faces, units, assembly placement |
| Not read | Colours, PMI and GD&T annotation, compressed .stpZ archives |
| File size | No fixed limit — past 100 MB you are told what it will cost this tab, then it opens |
Frequently asked questions
Is .stp the same as .step?
Yes, exactly. Both hold ISO 10303 part 21 text and either can be renamed to the other with no effect whatsoever. The three-letter form exists because MS-DOS allowed only three characters after the dot, and it survived in Windows CAD software long after the limit did. Anyone telling you the two are different formats is mistaken, though it is a very old and very widespread mistake.
Why do some programs only accept one spelling?
Because their import filter matches on the extension rather than the contents, which is lazy but common. If a program refuses your file, rename it to the other spelling and try again — that genuinely is the whole fix. Nothing inside the file needs to change, and no converter is involved.
What can I do with a .stp file?
Everything you would do with a solid model: machine it, quote it, measure it, modify it in any CAD package, or convert it to a mesh for printing. That is the point of the format — it is the one file every CAD system agrees on, so it moves a part between companies that share no software at all. What you cannot do is edit its feature history, because a STEP export is the finished shape rather than the recipe that produced it.
Does this open large assemblies?
There is no fixed ceiling. Past 100 MB the page describes what reading the file will cost before it starts, and proceeds on your say-so. Components are placed by the transforms the file stores rather than stacked at the origin, and the panel counts how many were found. A full product structure of several hundred megabytes will be slow rather than refused — opening one sub-assembly at a time stays the practical route, and is usually what you wanted to look at anyway.
Is my file uploaded anywhere?
No. The reader is JavaScript running in this tab, so the file never leaves your machine — there is no upload step to opt out of and no server that could keep a copy. For supplier drawings and unreleased parts that is the difference between a tool you can use at work and one you cannot.
About the extension nobody needed
The split between .stp and .step is one of the purest examples of a technical constraint outliving the technology. MS-DOS filenames allowed eight characters and three more after the dot, so a format published as STEP had to be written .stp on the machines that ran the CAD software of the day. Windows lifted the limit in 1995. Thirty years later the three-letter spelling is still what most Windows CAD packages export by default, and people still ask which of the two they were sent.
The answer that saves the most time is that it does not matter and you should stop checking. Every serious CAD package reads both. Where a program does refuse, renaming the file fixes it completely, because there is nothing to convert. This page exists under both spellings for the same reason your supplier's does: people search for the extension they are holding, not the one the standard uses.
What is worth your attention instead is what the file contains. See the STEP page for how exact surfaces differ from a mesh and why that difference decides whether a part can be machined, and the DXF viewer if what you were actually sent was a flat drawing rather than a solid.
Where your .stp is read
Every number on this page is worked out by JavaScript running in the tab you are reading it in. The model you open is read straight off your own disk — it is never uploaded, logged or kept, which is also why these tools carry on working after you disconnect from the network.
One clause specific to this page: files with this extension are usually supplier parts and unreleased designs. The reader runs in this tab, so nothing about the geometry, the filename or the header — which often names your company — is transmitted anywhere.