When Every Zstandard Library Failed on Android, I Built My Own

Meet unzstd - a pure Java Zstandard (zstd) decoder for Android and the JVM. What looked like a simple dependency turned into a surprisingly difficult problem. I needed to decompress zstd-compressed datasets in an Android app. Existing options all had major trade-offs: aircompressor 2.x depends on "sun.misc.Unsafe", which crashes on Android ART. aircompressor 3.x moved to "java.lang.foreign", which Android doesn't support. zstd-jni works well, but requires native ".so" files, ABI-specific packaging, and brings additional complexity with newer Android memory page requirements. I had to build a pure Java alternative so I ported aircompressor's decoder The result: ✅ No native code ✅ No "Unsafe" ✅ No "java.lang.foreign" ✅ Android API 26+ ✅ JVM 9+ ✅ Zero "Unsafe" references in the compiled bytecode (verified) To make sure it was actually correct, I differentially tested it against libzstd across compression levels 1-22, covering one-shot decompression, streaming, fuzzing, and corruption-boundary tests. It's decode-only, Apache 2.0 licensed, and completely open source. If you're building Android or Java applications that consume zstd-compressed data, I hope this saves you a few days of debugging. implementation("com.qyntrax:unzstd:0.1.0") GitHub: https://github.com/mbobiosio/unzstd Feedback, bug reports, and contributions are always welcome. Android #Java #Kotlin #OpenSource #JVM #Zstd #Compression