.jks

What is a .jks file?

JKS is Java's certificate and key storage format — a password-protected repository used by Java applications and servers.

Use caution
Type Security
By Sun Microsystems (now Oracle)
MIME application/x-java-keystore

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What is it

JKS is Java's answer to "where do I keep my certificates?" It's a password-protected binary file that stores multiple certificates and private keys, each identified by an alias. Java application servers (Tomcat, JBoss, WebSphere), Android apps, and any JVM-based service that needs TLS typically uses a JKS file.

The keytool command (included with every JDK) manages JKS files: creating keystores, importing certificates, generating key pairs, and listing contents. The command syntax is verbose (`keytool -list -v -keystore server.jks -storepass changeit`) but reliable. Every Java developer has typed these commands at some point.

JKS is being superseded by PKCS#12 (.p12) as the default keystore format in newer Java versions. Java 9+ uses PKCS#12 by default for new keystores. For existing JKS files, conversion is straightforward: `keytool -importkeystore -srckeystore old.jks -destkeystore new.p12 -deststoretype PKCS12`.

Technical details
Full Name
Java KeyStore
MIME Type
application/x-java-keystore
Developer
Sun Microsystems (now Oracle)
Magic Bytes
FE ED FE ED
Safety
.jks requires caution. Contains certificates and potentially private keys. Password-protected. Handle with the same care as P12/PFX files.
What opens it
keytool (JDK CLI)
FREE Windows / Mac / Linux
KeyStore Explorer
FREE Windows / Mac / Linux
FAQ
How do I view the contents of a JKS file?
`keytool -list -v -keystore server.jks` lists all entries with details. KeyStore Explorer (free GUI) provides a visual interface for browsing and managing JKS contents.
Should I use JKS or PKCS#12?
PKCS#12 (.p12) for new projects — it's the standard across platforms and the default in modern Java. Convert existing JKS to P12 with keytool -importkeystore.
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