What is a JSONLZ4 file?
A .JSONLZ4 file is a Compressed Firefox User Profile Data File created by Mozilla Firefox. The Mozilla web browser uses these files to store bookmark backups, session restoration data, and user preferences. The file contains standard JSON text data compressed with a customized LZ4 compression algorithm. The custom header prevents standard LZ4 extractors from opening it directly.
How to open JSONLZ4 files?
Because .JSONLZ4 uses a custom header, normal archive tools usually fail to extract the file. You must use specialized tools or scripts to read the contents. The website viewer.online/jsonlz4 analyzes .JSONLZ4 files to identify their exact format and creator software, shows which programs can open the file, and usually previews it.
Best practices and troubleshooting
Users often find .JSONLZ4 files in the `bookmarkbackups` folder of their Firefox user profile directory. If you need to read the data, do not edit the file directly in a text editor. This corrupts the compression. Instead, decode the file first. If your file fails to open, you can use viewer.online/jsonlz4 to verify the actual format of the file. You can also easily convert your decoded file to standard JSON or TXT formats on convert.guru.
Software and tools
You can restore these files natively through the Mozilla Firefox bookmark manager. Developers often use custom Python scripts, node.js modules, or command-line utilities like `dejsonlz4` or `lz4` (with header modifications) to decompress the data for manual inspection.
Summary
viewer.online/jsonlz4 directly opens and previews .JSONLZ4 files in the browser, eliminating the need to install software or troubleshoot compatibility issues.