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How to Use Free Online LZ4 Decompressor - Step by Step Guide

Step 1

Upload or Paste LZ4 Data

Start by providing the LZ4 compressed data you want to decompress. LZ4 is an extremely fast compression algorithm widely used in gaming, databases, and real-time applications. Perfect for decompressing JSON, XML, log files, and more:

•
Upload .lz4 file: Press "Upload .lz4" and pick the compressed file from your computer
•
Paste base64: Paste base64-encoded LZ4 data directly into the input area
•
Try sample data: Click "Sample" to see how decompression works with example data

Example: Base64 Encoded LZ4 Input

This is the Sample data: the JSON from Step 2 compressed into an LZ4 frame, then Base64-encoded. a standard LZ4 frame starts with "BCJNGG" in Base64:

BCJNGGxAogAAAAAAAABGjgAAAPAQewogICJnYW1l
IjogIkN5YmVyIEFyZW5hIDIwNzciLB4A8AFwbGF5
ZXJzIjogWwogICAgMwAAAgAwImlkNQChUExBWUVS
LTAwMS8AAAIAYyJ1c2VyblUAtlNoYWRvd05pbmph
IQBAc2NvcnMAQDk4NTBlAAACALEibGV2ZWwiOiA0
N2gAcH0KICBdCn0AAAAAOpAF5Q==
Step 2

Ultra-Fast Decompression

There's no button to press: as soon as the LZ4 data is in, it gets decompressed, the same way our GZIP, ZLIB, and Brotli decompression tools work:

•
Decompresses your data: Uses ultra-fast LZ4 algorithm for instant decompression
•
Checks the data: Header, block and content checksums are verified, so a damaged or cut-off file gives a clear error instead of half a result
•
Shows original content: Displays the decompressed data in an easy-to-read format

Example: Decompressed Output

After decompression, you'll see the original JSON data:

{
  "game": "Cyber Arena 2077",
  "players": [
    {
      "id": "PLAYER-001",
      "username": "ShadowNinja",
      "score": 9850,
      "level": 47
    }
  ]
}
Step 3

Download or Copy Decompressed Data

Get your decompressed data ready for use! Multiple options to work with your extracted content:

•
Copy to clipboard: One-click copying for immediate use in your projects
•
Download: Saves the decompressed bytes exactly, as a text file, or as a .bin file when the content is binary
•
View in editor: Read and review the content directly in the output panel

Frequently Asked Questions

How do I decompress an LZ4 file?

Press "Upload .lz4" and pick the file, or paste Base64-encoded LZ4 data into the input panel. There is no separate decompress button: it runs as soon as the data is in, and any text inside shows up in the output panel.

Is my data secure when decompressing?

Decompression runs in your browser, in the page's own JavaScript. The file or Base64 text you give it is not sent to our server.

Which kinds of LZ4 data can it read?

The .lz4 frame format that the lz4 command-line tool and most LZ4 libraries write, including frames with block or content checksums, several frames joined one after another, and the older legacy format from lz4 -l. It can't read raw LZ4 blocks that have no frame header, or frames that were compressed with a dictionary.

How do I compress files back to LZ4?

Use our LZ4 compression tool. LZ4 is lossless, so decompressing what it produces gives you back exactly the bytes you started with.

Why is LZ4 decompression so fast?

LZ4 gives up some compression ratio for speed. It has no entropy-coding stage, so decompressing is mostly copying bytes around, which is why file systems, databases and game engines use it for data that has to be read back quickly.

Can I paste LZ4 data taken from a database?

Only if it is stored as an LZ4 frame. Many databases, PostgreSQL among them, keep LZ4 data as raw blocks with their own headers instead, and those won't decompress here. If the data has no LZ4 frame header, the error message says so.

What happens if I upload an invalid LZ4 file?

You get a message saying what is wrong: the data is cut off, a checksum doesn't match (the file is damaged), the Base64 has a character that doesn't belong (with its line and column), or the data is something else, such as GZIP, ZIP or plain text. Nothing is shown as decompressed unless the whole file checks out.

What if the decompressed data isn't text?

Images, .tar archives and other binary files decompress too, but they can't be shown as text, so the output panel tells you the size instead. Download saves the exact bytes, named after the uploaded file without its .lz4 ending.

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