What is the LXF file format?
.lxf is a 3D LEGO project file created by LEGO Digital Designer (LDD). Each .lxf file is a single ZIP archive containing two entries: IMAGE100.LXFML (the model, written in LXFML - an XML dialect encoding every brick, colour and position) and IMAGE100.PNG (a preview image). Older files also include a MODEL100.MODEL entry.
LEGO Digital Designer was officially retired in 2022 and is no longer supported by the developer. BrickLink Studio (Stud.io) is the free official successor and imports .lxf files directly. LXF project files are saved in a Lego Creations folder in the user's Documents folder, with Models and Buildings subfolders storing all project-related files.
Because .lxf is a valid ZIP archive, renaming it to .zip lets you inspect the LXFML XML and the preview PNG inside with any archive manager.
Security & safety
RISK: LOWAn .lxf is a zip wrapping an XML model - data only, no executable code - so it is safe to open in LEGO software or extract as a zip. The only caution is that LDD itself is discontinued and no longer distributed by LEGO; avoid downloading "LDD installers" from random third-party sites (potential bundled adware/malware) - use the official BrickLink Studio instead, which is free, supported, and imports .lxf files.
Format details
in a nutshellFULL NAMELEGO Digital Designer Model Fileaka LEGO eXchange File, LDD model file
DEVELOPERThe LEGO Group (LEGO System A/S)since 2004 (LEGO Digital Designer); LXFML markup defined 2005
CATEGORY3D Image Files
MIME TYPEapplication/zip
TYPEZIP container holding an XML model (LXFML) plus a preview image (binary ZIP wrapping XML)
MAGIC BYTES · FILE SIGNATURE
OFFSET
00010203
HEX
504B0304
ASCII
PK··
An .lxf is a ZIP archive, so it starts with the ZIP "PK" signature like any zip. Identify it by its contents: IMAGE100.LXFML (the XML model) and IMAGE100.PNG (a preview), with older files also containing MODEL100.MODEL.
Programs that open LXF files
Windows2 apps
BrickLink Studio (Stud.io)
Free Install Studio (free), then File > Import > Import Model and select the .lxf. Studio is LEGO's official successor to LDD.
LEGO Digital Designer (legacy)
Free If you still have LDD installed, open the .lxf directly. LDD was discontinued and its site closed Jan 31, 2022, so it can no longer be downloaded officially - use Studio for new installs. 
macOS2 apps
BricksViewer
Open-source Open-source viewer that can read .lxf models for viewing (no editing). Aging but free.
BrickLink Studio (Stud.io)
Free Install Studio, then File > Import > Import Model and choose the .lxf. 
Linux1 app
BricksViewer
Open-source Open the .lxf to view the model. Free/open-source; not actively developed but functional.
Web1 app
Mecabricks / LDraw-based viewers
Free Web-based LEGO building tools; convert/import LDD models (often via LDraw .ldr) to view in the browser. Technical details
deep spec| Container format | ZIP archive - a valid ZIP starting with the PK magic signature |
| Magic bytes | 50 4B 03 04 at offset 0 - standard ZIP local file header |
| Compression | DEFLATE (per-entry ZIP compression) |
| Byte order | Little-endian (ZIP structures) |
| MIME type | application/zip |
| Primary model entry | IMAGE100.LXFML - UTF-8 XML describing every brick, colour and position |
| Preview entry | IMAGE100.PNG - rendered thumbnail embedded in the archive |
| Legacy entry | MODEL100.MODEL - present in files saved by older LDD versions |
| XML dialect | LXFML (LEGO eXchange Format Markup Language) |
| LXFML version range | 1.0 (2005) through 5.0 (LDD 4.3, 2016) |
| Brick encoding | Part ID, official LEGO colour code, and 4×4 transformation matrix per brick |
| File integrity | Per-entry CRC-32 (ZIP standard) |
| Typical file size | Tens of KB to a few MB, scaling with brick and submodel count |
| Supported platforms | Windows, macOS (original LDD); cross-platform via BrickLink Studio |
| Current importer | BrickLink Studio (Stud.io) - official successor, imports .lxf natively |
| Released | 2004 (LEGO Digital Designer); LXFML markup defined 2005 |
| Latest version | LXFML 5.0 (LDD 4.3, the final LDD release, 2016) |
| Specification | wiki.ldraw.org |
LXF conversions
Possible
.LXF .ZIPGUIDE
Yes - rename the file from .lxf to .zip and open it with 7-Zip, WinRAR, or Windows Explorer.
How to convert
.LXF .LXFMLGUIDE
Yes - rename the .lxf to .zip and extract IMAGE100.LXFML with any archive tool. No software installation…
How to convert
.LXF .LDRGUIDE
You can convert LXF to LDR by importing the file into BrickLink Studio (free) and exporting it as an LDraw…
How to convert
.LXF .PNGGUIDE
Yes, LXF converts to PNG -- the fastest method is to rename the .lxf to .zip and extract IMAGE100.PNG, which…
How to convert
.LXF .STLGUIDE
Yes, LXF can be converted to STL - the fastest route is BrickLink Studio (free): import the .lxf, then export…
How to convert
.LXF .IOGUIDE
Yes, you can convert LXF to IO - open the file in BrickLink Studio (free) and save it as .io.
How to convert
Community Q&A
asked by usersNo questions yet - be the first to ask about LXF files.
Frequently asked questions
How do I open an .lxf file now that LEGO Digital Designer is gone?
Use BrickLink Studio (free, LEGO's official successor): File > Import > Import Model and select the .lxf. If you still have an old LDD install it opens .lxf directly, but LDD can no longer be downloaded officially (site closed January 31, 2022).
What is an .lxf file?
It's a LEGO Digital Designer model - a virtual LEGO build saved as a ZIP that contains an XML description of every brick (IMAGE100.LXFML) plus a preview image. It's a model definition, not a rendered picture.
Can I open an .lxf without any LEGO software?
You can inspect it: rename the .lxf to .zip and open it with any archive tool to read IMAGE100.LXFML (the XML model) in a text editor. To actually view/build the model in 3D, use BrickLink Studio.
How do I convert an .lxf to BrickLink Studio?
Open Studio and use File > Import > Import Model on the .lxf, then Save As .io (Studio's format). This is the recommended way to migrate old LDD models into the maintained app.
How do I get a parts list to build the model for real?
Import the .lxf into BrickLink Studio, which can generate a Bill of Materials / parts list and even link to BrickLink to source the pieces.
Is .lxf the same as .lxfml?
Closely related: .lxf is a ZIP containing the .lxfml XML model plus a preview. The .lxfml is the raw, uncompressed XML. You can extract one from the other by zipping/unzipping.
References
1FileInfo - LXF (LEGO Digital Designer Model File)fileinfo.com
2LDraw.org Wiki - LXF / LXFML formatwiki.ldraw.org
