application/java-archive

Java's deployment unit since the nineties: classes, resources and an optional META-INF/MANIFEST.MF in what the specification plainly calls a zip file with conventions. That ancestry is the whole sniffing story — a JAR opens with the same PK bytes as every other zip, and only the manifest or the .class entries inside give it away, so no signature is listed here. Serve downloads as application/java-archive rather than application/zip if you want clients to treat them as runnable artifacts; the old x-java-archive spelling still appears in ancient server configs.

.war and .ear, the servlet and enterprise packagings, ride on the same type — they are JARs with stricter internal layouts.

Defined by JAR File Specification (Java SE 21) · IANA registration. Registry facts from the IANA media-types registry via mime-db.