If you’ve received a LAZ file and aren’t sure what to do with it — or if you’re a surveyor trying to explain the format to a client — this is the explainer you need.
What is a LAZ file?
LAZ is a losslessly compressed version of the LAS (LASer) file format. Both formats store point cloud data — collections of georeferenced 3D points, each with XYZ coordinates and typically additional attributes like colour (RGB), intensity, and classification.
LAS was developed by the American Society for Photogrammetry and Remote Sensing (ASPRS) as an open standard for LiDAR data interchange. It’s been the dominant format for point cloud data since version 1.0 was released in 2003.
LAZ was developed by Martin Isenburg as a lossless compression extension to LAS. A LAZ file contains exactly the same data as the equivalent LAS file — nothing is lost in the compression — but is typically 10-20% the file size.
What’s inside a point cloud?
Each point in a LAS/LAZ file can contain:
| Attribute | Description |
|---|---|
| X, Y, Z | 3D coordinates (in a specified coordinate reference system) |
| Intensity | Return signal strength (0-65535 typically) |
| Return number | Which return this point represents (for multiple-return LiDAR) |
| Number of returns | Total returns from this pulse |
| Classification | What the point represents (ground, vegetation, building, etc.) |
| Red, Green, Blue | Colour values (if captured with a colour camera) |
| GPS time | Timestamp of the pulse |
| Scan angle | Angle at which the laser was fired |
In a typical LiDAR survey:
- Ground returns (classification 2) are used for Digital Terrain Model generation
- Building returns (classification 6) are used for building footprint extraction
- Vegetation returns (classifications 3, 4, 5) are used for canopy height modeling
- Unclassified returns (classification 1) may include everything that hasn’t been processed
In a photogrammetry point cloud, most points are unclassified (class 1) with RGB colour values derived from the drone imagery.
LAS versions
The current widely-used version is LAS 1.4 (released 2011). Most tools support LAS 1.2 and 1.4. Older 1.0 and 1.1 files are increasingly rare but still encountered in historical datasets.
For new deliverables, produce LAS 1.4 / LAZ (LASzip compression).
How to open a LAZ file
| Software | Cost | Platform |
|---|---|---|
| CloudCompare | Free, open source | Win/Mac/Linux |
| QGIS | Free, open source | Win/Mac/Linux |
| LAStools | Free for basic tools | Win |
| ArcGIS Pro | Subscription | Win |
| Global Mapper | ~$500/yr | Win |
| FugroViewer | Free | Win |
| Potree | Free, open source (browser) | Any (via web server) |
For most users, CloudCompare is the best free option. It handles large LAZ files well and provides measurement, sectioning, and colouring tools.
For clients without any GIS experience, none of these are practical — which is why browser-based delivery (see below) is important.
What’s the difference between LAS and LAZ?
Functionally: nothing. The data is identical. LAZ is just a compressed version.
Practically:
- File size: LAZ is typically 10-20% the size of the equivalent LAS file
- Compatibility: All modern point cloud tools support LAZ. Some older tools require LAS — you can convert with LASzip or PDAL
- Processing speed: Some tools process LAS slightly faster than LAZ (no decompression overhead), but the difference is usually negligible
Always deliver LAZ over LAS unless a client specifically requires LAS. There’s no reason to deliver a 10 GB LAS file when a 1.5 GB LAZ file contains the same data.
Converting between LAS and LAZ
The simplest tool is LASzip, the free command-line utility from Martin Isenburg:
# LAS to LAZ
laszip -i input.las -o output.laz
# LAZ to LAS
laszip -i input.laz -o output.las
PDAL (open source) handles the conversion too:
pdal translate input.las output.laz
Common LAZ file sizes
As a rough guide:
| Survey type | Typical LAZ size |
|---|---|
| Single building LiDAR scan | 50-500 MB |
| Small construction site drone survey | 200 MB – 2 GB |
| Medium LiDAR corridor (1-10 km) | 500 MB – 5 GB |
| Large area airborne LiDAR | 5-50 GB |
| Underground mine LiDAR | 1-10 GB |
Sharing LAZ files with clients
LAZ files are too large to email and require specialist software to view. Your options:
- Dropbox/Google Drive: Works for storage and download, but the client still needs software to open the file
- Convert to a browser-based format: Use PotreeConverter to create a streamable Potree dataset, then host it
- Use a spatial data delivery platform: Upload to Swyvl (or similar) and share a link — the client sees the point cloud in a browser without installing anything
For professional delivery to non-technical clients, option 3 is the practical choice. The browser-based Potree viewer allows clients to orbit, zoom, measure, and cross-section the point cloud — all in their browser, on any device.
FAQ: Is LAZ the same as LAS 1.4?
No. LAZ is a compression format that can be applied to any LAS version. A LAZ file might contain LAS 1.0, 1.2, or 1.4 data — the version is a separate attribute from the compression.
FAQ: Can I open a LAZ file in QGIS?
Yes. QGIS has supported LAZ files natively since version 3.18 via PDAL integration. You can add a LAZ file as a point cloud layer and visualise it in 2D or 3D.
FAQ: Can I view a LAZ file in my browser?
Not directly — but you can convert it to Potree format (using PotreeConverter) and serve it via a web server, or upload it to a platform like Swyvl that handles the conversion and serving automatically.