ZIP
Most-used archive format. Phil Katz, PKWARE, 1989 (for MS-DOS PKZIP). Per-file compression with DEFLATE. Cross-platform standard. Spec open since 1989.
JAR (Java), DOCX/XLSX/PPTX (Office Open XML), APK (Android), EPUB are all ZIP files with specific naming conventions. Compression: DEFLATE default (LZ77 + Huffman). Later additions: BZIP2, LZMA, Zstandard (in ZIP64). 4 GB limit can be bypassed with ZIP64. Competitors: 7z (better compression), tar+gzip (Unix standard), rar (proprietary). In CTF/security: ZIP bombs (42.zip → 4.5 PB), header manipulation, polyglot files.