ZIP
The archive that ate the world, one PK header at a time.
Where it came from
Phil Katz created ZIP in 1989 after a lawsuit with SEA (makers of ARC) — he wrote PKZIP from scratch in jail-released time, and the format's header magic `PK` are his initials. Katz's story ended tragically, but his format became the universal archive: DOS, Windows, Java JAR, Office DOCX, Android APK — all ZIP containers underneath.
How it works
A ZIP is a list of local file entries (name + compressed bytes) followed by a central directory at the end — that's why tools can list contents without reading the whole file, and why a truncated ZIP can sometimes be repaired.
Most entries use DEFLATE (the same algorithm as gzip). Entries are independent, so extraction can be lazy and parallel.
Danger notes: zip bombs (tiny archive, petabytes unpacked) and path traversal (`../../etc/passwd` names) are real attack vectors — any extractor must cap totals and sanitize paths. UWC unpacks in your browser with fflate, nothing touches a server.
Unpack ZIP archives
Drop a ZIP, browse the file list, download individual files — all client-side, no upload.