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LidarKit

What is a LAZ file?

A losslessly compressed LiDAR point cloud — and how to open one.

A LAZ file (.laz) is a LiDAR point cloud stored in the LASzip compression format: a lossless, open compression of the ASPRS LAS format. It holds exactly the same points, attributes and metadata as the equivalent LAS file, usually at 10 to 20 percent of the size.

If a national mapping agency or survey provider handed you LiDAR data, there is a good chance it arrived as LAZ — the size difference is large enough that most public data portals distribute the compressed form.

Which software opens a LAZ file

Most current GIS and point cloud software reads LAZ natively, and the viewer here opens one in the browser with nothing installed. Support is broad but not universal: older desktop GIS releases, a number of CAD import paths and plenty of in-house scripts still expect uncompressed LAS, and that gap is the usual reason anyone converts.

If your software will not open it

Decompress it to LAS. The two formats hold identical data, so this costs you nothing but disk space, and it is usually faster than changing software mid-project.

Convert your LAZ to LAS here — it runs in your browser, so the file is not uploaded anywhere and there is no fixed size limit.

Technical detail

  • Extension: .laz. Compressed LAS versions 1.0 through 1.4.
  • Compression: lossless, using an arithmetic coder over the differences between neighbouring points. There is no quality setting because nothing is discarded.
  • Open standard: the specification and reference implementation (LASzip) are public and open source, with several independent implementations — including laz-perf, the library this site runs on.
  • Contents: a public header block, variable length records holding the coordinate reference system, then compressed point records carrying position, intensity, return number, classification, GPS time and any extra bytes.
  • Related: COPC (.copc.laz) is a spatially-indexed reorganisation of LAZ for streaming subsets from cloud storage. Same compression, different layout.

Frequently asked questions

What is a LAZ file?
A LAZ file is a LiDAR point cloud stored in the LASzip compression format — a lossless, open compression of the ASPRS LAS format. It contains exactly the same data as the equivalent LAS file, typically at 10 to 20 percent of the size.
How do I open a LAZ file?
Most current GIS and point cloud software reads LAZ natively, and the viewer on this site opens one in the browser with nothing installed. If a tool refuses the file, decompress it to LAS with the converter here — LAZ and LAS hold identical data, so nothing is lost either way.
Can I open a LAZ file in CAD software?
Not always directly — LAZ support in CAD packages varies by product and version, and several import paths still expect uncompressed LAS. Converting to LAS first is the reliable route, and it is why LAZ-to-LAS conversion is such a common request among CAD users.
Is LAZ the same as LAS?
The data is the same; the encoding is not. LAZ is a compressed container for exactly the LAS byte layout, so converting between them changes only the file size. LAZ is the better choice for storage and transfer, LAS for tools that cannot read compressed input.
Why is my LAZ file so much smaller than the LAS it came from?
Because neighbouring LiDAR points are highly correlated, and LASzip encodes the differences between them rather than each full value. That routinely yields an 80 to 90 percent reduction with nothing discarded — it is lossless, not lossy compression.

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