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LidarKit

Convert LAZ to LAS in your browser

Also LAS to LAZ. Byte-identical, no size limit, nothing uploaded.

Drop your LAS or LAZ file here

or choose a file

LAS 1.0–1.4 · multi-gigabyte files welcome

No upload. Conversion 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 before doing anything.
  2. Press Convert. The direction is taken from the file itself — a .laz input decompresses to .las, a.las input compresses to .laz.
  3. Download the result. Your original file is untouched.

Your file never leaves your device

This is a static site with no backend. There is no upload endpoint to send a file to, and no account to create. When you press Convert, the file is read in chunks through the browser's File API and passed to a WebAssembly build of laz-perf running in a Web Worker on your own machine.

Because nothing is transmitted, the practical consequence is that this works for data you are not allowed to upload anywhere — client survey data, infrastructure scans, anything under an NDA. It also keeps working with your network disconnected once the page has loaded. See how it works for the mechanism in detail.

What is preserved

Conversion in both directions is lossless, and the round-trip is verified byte-for-byte in the test suite rather than simply claimed:

  • The original public header block, unmodified.
  • All user VLRs and EVLRs, which is where the coordinate reference system lives — as GeoTIFF keys or a WKT string.
  • Every point record, including extra bytes and user-defined fields.
  • Classification, return numbers, intensity, GPS time, scan angles.

That second point is worth dwelling on. The straightforward way to build a browser LAZ converter is to hand the file to laz-perf's own file writer, which rewrites the header and drops every user VLR — so the output loads, looks fine, and has quietly lost its coordinate system. This converter assembles the LAZ container itself specifically to avoid that.

Supported formats

FeatureSupportedNotes
LAS 1.0 – 1.4YesVersion preserved on output. Round trip test-verified on 1.2, 1.3 and 1.4.
Point formats 0–3YesByte-identical round trip verified in the test suite
Point formats 6–8YesLayered LAZ variants, converted both ways. Not yet covered by the round-trip test.
Point formats 4, 5, 9, 10NoFull waveform data — a laz-perf limitation. Detected and reported before conversion starts.
Extra bytesYesPreserved exactly
VLRs / EVLRs / CRSYesPreserved byte-for-byte
Files over 4 GBYesChunked read, disk-backed output

Just want to look at a file?

Conversion is not always the question. To check what a delivery actually contains, open it instead: the LAS and LAZ viewer draws the point cloud in 3D and colours it by elevation, intensity or classification, and the GeoTIFF viewerhillshades a DEM, shows it as a 3D surface, and drapes the matching orthophoto over it. Both run on your own machine, like everything else here.

LAS or LAZ — which should you keep?

Keep LAZ for storage, archiving and transfer: it is lossless, so there is no data-integrity reason to prefer LAS, and it is typically five to ten times smaller. Convert to LAS only when a specific tool in your chain cannot read compressed input. The full comparison covers read performance and where each format actually costs you something.

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.
Is the conversion lossless?
Yes, and it is verified rather than asserted: the test suite checks that a LAS file converted to LAZ and back is byte-for-byte identical to the original, including the header, all VLRs and EVLRs, and every point record. LAZ is a lossless compression format, so no coordinate or attribute precision is lost in either direction.
Are my files uploaded anywhere?
No. There is no upload endpoint and no server component — the page is a static site, and conversion runs in a Web Worker on your own machine using WebAssembly. Once the page has loaded it will keep working 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.
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 compression does not support; the converter detects those and tells you before starting rather than producing a broken file.
How much smaller is LAZ than LAS?
LAZ files are typically 10 to 20 percent of the size of the equivalent LAS file, so a 1 GB LAS commonly compresses to roughly 100–200 MB. The exact ratio depends on point density, how many attributes are populated, and the coordinate scale factors in the header.
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.
Which browsers does this work in?
Any current version of Chrome, Edge, Firefox or Safari. Chromium-based browsers additionally support the synchronous private-file-system API used for disk-backed output, which is what makes very large files practical; other browsers fall back to assembling the result in memory.