The only online tool that decompiles two JARs to Java source and diffs the actual code. See every changed class, method, and line.
Drop old and new versions of your .jar file into the upload areas.
Both JARs are decompiled to Java source using FernFlower with CFR fallback.
View a file-by-file diff of every changed, added, or removed Java class.
Traditional JAR comparison tools like JarComp, japicmp, or zipdiff show binary-level differences: which files changed size, which checksums differ, or which API signatures were modified. But they don't tell you what actually changed in the code.
This tool decompiles both JAR files to Java source code and then generates a unified diff, exactly like running diff on two source trees. You see which classes changed, which methods were modified, and which lines of code differ. This is invaluable for:
Other tools that compare JAR files either require local installation (JarComp, Beyond Compare, IntelliJ IDEA) or only compare at the metadata level (japicmp compares API signatures, zipdiff compares archive entries). No other online tool decompiles JARs to Java source and shows a line-by-line code diff. This tool runs entirely in your browser with no software to install.
Upload the original JAR on the left and the modified JAR on the right. Both files are decompiled to Java source code using FernFlower, then a unified diff is generated showing every changed class and method.
Yes. The decompiler handles obfuscated bytecode and produces readable output. While obfuscated class and method names may look like random characters, the diff will still show exactly what changed between versions.
JARs are decompiled using FernFlower with an automatic fallback to CFR if FernFlower fails on a particular class. This ensures maximum coverage across different Java bytecode patterns.
Download both versions of the library JAR (e.g. from Maven Central), upload the old version on the left and the new version on the right. The tool will decompile both and show you every changed class, method, and line of code.
The upload limit is 1 GB. Large JARs may take longer to decompile, but you can start browsing partial results while decompilation continues in the background.
Yes. This is a web-based tool that works in any modern browser on any operating system including macOS, Linux, Windows, and even mobile devices.
Yes. Uploaded files are stored temporarily for decompilation and comparison, then automatically deleted. Files are never shared with third parties.