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LidarKit

Convert LAZ to LAS

Decompress a LAZ point cloud back to uncompressed LAS. Runs on your machine — no upload, no fixed size limit.

Drop your LAS or LAZ file here

or choose a file

LAS 1.0–1.4 · multi-gigabyte files welcome

No upload. Processing runs in a Web Worker on your device — this app has no server component and no upload endpoint. How it works

How to convert LAZ to LAS

  1. Drop your .laz file onto the box above, or click it to choose a file. The converter reads the header and shows you what is inside — version, point format, point count, extents and coordinate system — before doing anything to it.
  2. Press Convert. The direction is taken from the file itself, so a .laz input decompresses to .las and a .las input compresses to .laz.
  3. Download the result. Your original file is untouched.

When you actually need this

LAZ is the better format to store and share — it is lossless and typically five to ten times smaller. You generally need an uncompressed LAS for one reason: something in your toolchain refuses the compressed form. The common cases:

SoftwareReads LAZ?What to do
QGIS 3.18+YesNative via PDAL. If it fails, the build may lack PDAL support — convert to LAS.
QGIS below 3.18NoConvert to LAS, or upgrade.
ArcGIS ProYesVia LAS dataset tools. Convert LAS in Geoprocessing also does it, but needs a valid spatial reference.
ArcMapNoConvert to LAS first.
AutoCAD / Civil 3DPartlyReCap ingestion varies by version; uncompressed LAS is the reliable path.
CloudCompareYesNo conversion needed.

The problem to watch for: a lost coordinate system

The failure that costs people the most time is not a conversion that errors — it is one that succeeds and silently drops the coordinate reference system. Your points end up in the right relative positions and the wrong place on Earth, and you usually find out much later.

The CRS lives in the file's variable length records, as GeoTIFF keys or a WKT string. Several conversion routes rewrite the header and discard user VLRs along the way. This converter preserves the header, VLRs and EVLRs byte-for-byte, which is the specific reason it assembles the container itself instead of delegating to laz-perf's own file writer.

When to use this

When you do not want to install anything, or the data cannot be uploaded to a third party, or the file is larger than an online converter will accept.

Frequently asked questions

How do I convert a LAZ file to LAS?
Drop the .laz file onto the converter above and press Convert — the direction is detected from the file itself, and you get a .las file back to download. Nothing is installed and nothing is uploaded.
Why do I need to convert LAZ to LAS at all?
Because some tools still cannot read compressed point clouds. LAZ is lossless and smaller, so it is the better format to keep — but older QGIS builds, several CAD import paths, and some proprietary survey packages only accept uncompressed LAS, and converting is faster than changing software.
Will converting LAZ to LAS change my data?
No, and it is verified rather than asserted: the test suite checks that a LAS file compressed to LAZ and decompressed again is byte-for-byte identical to the original, including the header, all VLRs and EVLRs, and every point record. LAZ is a lossless compression of exactly the LAS byte layout, so the only thing decompression changes is the file size, which grows by roughly five to ten times.
Are my files uploaded anywhere?
No. There is no upload endpoint and no server component — this page is static, and the conversion runs in a Web Worker on your own machine using WebAssembly. Once the page has loaded it will keep converting with your network disconnected.
What is the maximum file size?
There is no fixed limit. Input is read in chunks and output is streamed to a temporary file in the browser's private file system, so peak memory stays at a few megabytes regardless of whether the file is 50 MB or 50 GB. The practical limit is your available disk space — and remember the LAS output will be several times larger than the LAZ input.
Does it keep the coordinate reference system (CRS)?
Yes. The original header, all user VLRs and EVLRs — which is where the CRS is stored, as either GeoTIFF keys or a WKT string — are preserved byte-for-byte. This matters because the obvious way to build this tool silently discards user VLRs, and with them the coordinate system.
Which LAS versions and point formats are supported?
LAS 1.0 through 1.4, with point data record formats 0, 1, 2, 3, 6, 7 and 8, including extra bytes. The byte-identical round trip is explicitly verified in the test suite for LAS 1.2, 1.3 and 1.4 on formats 0 to 3. Point formats 4, 5, 9 and 10 store full waveform data, which laz-perf does not support; the converter detects those and tells you before starting rather than producing a broken file.
How long does it take?
Typically seconds rather than minutes for a file of a few hundred megabytes, and it scales linearly with file size. Because the work happens on your own machine there is no queue and no upload time, which usually makes it faster end-to-end than a server-based converter for large files.
How much bigger will the LAS file be?
Typically five to ten times the size of the LAZ, because LAZ files are usually 10 to 20 percent of the equivalent LAS. The exact ratio depends on point density, how many attributes are populated, and the coordinate scale factors in the header — a file with tightly scaled coordinates and few populated attributes compresses much better than one without.
Can I open a LAZ file directly in QGIS or ArcGIS Pro?
Recent versions of both read LAZ natively — QGIS since 3.18 via PDAL, and ArcGIS Pro through its LAS dataset tools. Older versions, and many CAD packages including some Civil 3D workflows, still require an uncompressed LAS, which is the usual reason people need this conversion. The table on this page lists the common cases.
Which browsers does this work in?
Any current version of Chrome, Edge, Firefox or Safari. Current versions of all of them support the synchronous private-file-system API used for disk-backed output, which is what makes very large files practical; where it is missing the converter falls back to assembling the result in memory.

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