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View a ULZ file online, free

Open and read .ULZ files online. View source, logs and text with syntax highlighting, search and line numbers, free.

Drop your .ULZ file here

Opens your .ULZ file right here.

Choose file
Up to 50 MB · 160+ text and code extensions
Instant. Opens in seconds
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100% free. No limits on use

What you get for a .ULZ file

We don't have a dedicated viewer for this format, so we identify and inspect it instead — honestly, only what can be read from the file.

01

Drop your .ULZ file

Choose it or drag it in. It's read right here in your browser.

02

We identify it

We read the magic bytes to tell what the file really is, its MIME type, and whether the name matches the contents.

03

See the details

Any metadata we can extract (dimensions, EXIF/GPS, document author and dates), a hex view, plus readable text and strings found inside.

What is a .ULZ file?

Plain text that programs, servers and people write every day.

A .ULZ file is a USBlyzer Data Capture File used for storing captured USB traffic information. These data files contain logs of activity and communication between USB devices and a computer system. They are specifically designed to be opened and analyzed using the USBlyzer software.

Programs that open .ULZ files

Windows
USBlyzer
.ULZ format details
DeveloperUSBlyzer

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Frequently asked questions

Is my .ULZ file uploaded anywhere?

No. The file is read and highlighted for you.

Why do some characters look wrong (é, ł)?

That usually means the file was saved in one encoding and opened in another. We detect UTF-8, UTF-16 and the Windows-1250/1252 code pages automatically and show which one was used.

Can it handle huge log files?

Yes, up to 50 MB. Only the lines on screen are drawn, so scrolling stays smooth. Syntax colours are switched off for files over 1.5 MB to keep things fast.

How do the log level filters work?

We find levels like ERROR, WARN, INFO and DEBUG on each line. Lines without a level, such as stack traces, stay with the entry above them, so filtering to errors keeps the full trace.

Can I edit the file?

This is a viewer. To change code, download it or copy it into your editor. Converting encodings and line endings is planned.

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