How to open a code or text file online
Three steps, a few seconds, no software.
Open your .CLASS file
Drop it on the box, choose it from your device, or paste the text straight in.
View it instantly
Your .CLASS file opens neatly formatted with line numbers.
Search, copy or download
Search the text, jump to any line, then copy what you need or download a clean copy.
What is a .CLASS file?
Plain text that programs, servers and people write every day.
A CLASS file is compiled Java bytecode, the output javac produces from a .java source file. To run it you need Java (a JDK) installed, then use the command "java MyClass". To read what the code does, open it in a decompiler such as JD-GUI. CLASS files are not documents; double-clicking one in a file manager will not open it usefully.
Programs that open .CLASS files
| Full name | Java Bytecode Class File |
|---|---|
| Developer | Sun Microsystems (now Oracle); part of the Java Platform |
| First released | 1995-1996 (Java 1.0) |
| Category | Text & Code |
| MIME type | application/java-vm |
| Signature | CA FE BA BE "ʾº¾" - the literal "CAFEBABE" magic number |
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Frequently asked questions
Is my .CLASS 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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