What the Packer did
Dean Edwards released his JavaScript Packer around 2004. It applied two techniques: replacing repeated strings with variables and encoding the result in base62. The browser then executed a small decompression routine at load time. For its era, it produced smaller payloads than simple whitespace removal.
Why it disappeared
The decompression step added parse and execution cost on every page load. As JavaScript engines improved, parse time became a larger share of startup latency. Tools like UglifyJS and later Terser achieved comparable size reductions through dead-code elimination, mangling, and structural transforms without requiring client-side unpacking. Build pipelines also shifted toward ahead-of-time optimization.
Modern context
If you encounter Packer-obfuscated code in a legacy codebase, treat it as technical debt. Source maps and modern minification make the trade-off obsolete. The packer's website has been offline for years, and the original repository is archived.