# How to send STL files

STL (Stereolithography mesh) files are often too big for email and chat apps. Here is how big they get and how to send them exactly as they are.

_Source: https://sharelargefilesfree.com/send-stl-files · Updated 2026-10-13_

**Quick answer:** To send a large STL file, upload it to Share Large Video Files (up to 20 GB, no account) and share the download link: the file arrives unchanged. A 1-million-triangle STL model is about 50 MB, more than most email providers accept.

## What is a STL file?

STL is the standard file for 3D printing. It describes the surface of an object as a mesh of triangles, with no colour or material. Makers, product designers, dentists and print services use it to send models to slicers such as Cura, PrusaSlicer and Bambu Studio.

STL size depends on the number of triangles. A binary STL uses 50 bytes per triangle, so a million-triangle 3D scan or sculpt is about 50 MB. Text (ASCII) STLs of the same model are several times larger.

Extensions: .stl, .3mf.

## How big are STL files?

| File | Typical size |
| --- | --- |
| A simple mechanical part | about 100 KB to 5 MB |
| A detailed miniature or figurine | roughly 20 to 100 MB |
| A 1 million triangle mesh (binary STL) | about 50 MB |
| A high-resolution 3D scan | roughly 100 MB to 1 GB |

## Which apps can send one?

Can you send a 1-million-triangle STL model (about 50 MB) as an attachment?

| App | Limit | Fits? |
| --- | --- | --- |
| Gmail | 25 MB per email | No, send a link |
| Outlook.com | 20 to 25 MB per email | No, send a link |
| WhatsApp (document) | 2 GB per file | Yes |
| Telegram | 2 GB per file | Yes |
| Facebook Messenger | 100 MB per file | Yes |
| Discord (free) | 20 MB per file | No, send a link |
| Slack | 1 GB per file | Yes |
| WeTransfer (free) | 3 GB per transfer | Yes |
| **Share Large Video Files** | 20 GB per transfer | Send the link anywhere |

Limits from our [file size limits by app](https://sharelargefilesfree.com/file-size-limits-by-app) table, checked against each service's help pages.

## How to send STL files without changing them

1. Open [Share Large Video Files](https://sharelargefilesfree.com/) in any browser and choose **Get a link** (or **Send by email**).
2. Drop STL files on the upload box, or pick a whole folder. Up to 20 GB and 1000 files per transfer.
3. Optional: add a password, a download limit or an expiry under More options.
4. Copy the link (or show the QR code) and send it by chat or email. The recipient downloads the original file, byte for byte.

## Tips for sending STL files

- Save as binary STL rather than ASCII; it is several times smaller.
- Zip STL files before sending, meshes often compress well.
- Tell the recipient the units (millimetres or inches), because STL does not store them.
- Consider 3MF if the recipient's slicer supports it; it can keep colours, units and print settings.

## How to open a STL file

Slicers such as **Cura**, **PrusaSlicer** and **Bambu Studio** open STL on Windows and Mac. Blender and most CAD apps import it. On phones, free 3D viewer apps are needed.

## Frequently asked questions

### Why is my STL file so large?

It has a very high triangle count, often from a 3D scan or sculpt, or it was saved in ASCII. Binary STL at 50 bytes per triangle is the compact option.

### Does an STL file store units?

No. STL has no units, so a model made in inches can import tiny in a millimetre-based slicer. Always tell the recipient the units.

### Should I zip STL files before sending?

Yes. STL files often shrink a lot in a zip, and several parts arrive as one download.