What is the JKS file format?
A .jks file is a Java KeyStore - a proprietary binary container that stores cryptographic private keys and X.509 certificates for use by Java applications. The format was introduced by Sun Microsystems as part of the Java Cryptography Architecture (JCA) in the late 1990s and is maintained today by Oracle.
Every .jks file starts with the 4-byte magic number 0xFEEDFEED, followed by a version field (typically 0x00000002). The file is big-endian and holds two entry types: KeyEntry records, containing an encrypted private key plus its certificate chain, and TrustedCertEntry records, which store certificates without encryption. A keyed SHA-1 digest at the end protects integrity - a wrong password or any tampering triggers the familiar *"keystore was tampered with, or password was incorrect"* error.
Private keys are protected by a proprietary password-based encryption (PBE) scheme built on SHA-1, which is considered weak by modern standards. The .jks format is Java-only and not readable by tools such as OpenSSL, which expect PKCS#12 or PEM instead.
Since JDK 9 (2017), Oracle deprecated .jks in favour of .p12 / .pfx, which became the new default keystore type. keytool now emits a migration warning on every JKS store it opens. The JDK's system trust store cacerts has historically shipped as a .jks file. The related .jceks variant (magic 0xCECECECE) offers stronger Triple-DES key protection but remains equally Java-specific.
Security & safety
RISK: MEDIUMA JKS file is inert data (no executable code), but it is a SECRET store: it commonly contains private keys whose exposure compromises a server's identity or an app's signing key. Treat it like a password file - never commit it to a public repo, restrict file permissions, and use a strong store password. The format's encryption is weak by modern standards, so a leaked .jks with a poor password can be brute-forced; this is a further reason to migrate to PKCS#12 and to rotate keys if a keystore is ever exposed. Files claiming to be keystores from untrusted sources should not be trusted as your trust store.
Format details
in a nutshell- Star Wars Jedi Knight game save - Some LucasArts/Raven Star Wars Jedi Knight titles used .jks for saved games; loaded inside the game, unrelated to Java keystores (the obsolete db_name).
Programs that open JKS files
Windows3 apps
keytool (JDK)
Free Run 'keytool -list -v -keystore file.jks' (you'll be prompted for the store password) to view entries; -importcert / -genkeypair to modify.
KeyStore Explorer
Open-source Open the .jks in this GUI, enter the password, and browse/edit keys and certificates without memorizing keytool syntax.
Star Wars Jedi Knight (game saves)
Paid Only relevant if the .jks is actually a Jedi Knight game save (see also_used_by) - those load inside the game, not via keytool. 
macOS2 apps
keytool (JDK)
Free Same keytool commands; install a JDK (Temurin/Oracle) and run 'keytool -list -keystore file.jks'.
KeyStore Explorer
Open-source Cross-platform Java GUI; open the .jks and enter its password to inspect/manage entries. 
Linux2 apps
keytool (JDK)
Open-source Install a JDK (e.g. Temurin/OpenJDK) and use keytool to list, import, export, or convert the keystore. Technical details
deep spec| Magic bytes | 0xFEEDFEED (FE ED FE ED) at file offset 0; identifies the file as JKS to tools and validators |
| Format version field | 4-byte big-endian integer at offset 4; value 1 or 2 (version 2 is current) |
| Byte order | Big-endian throughout the entire binary structure |
| Private-key encryption | Proprietary PBE scheme using SHA-1 as a key-derivation primitive; considered cryptographically weak by modern standards |
| Certificate storage | TrustedCertEntry records hold X.509 DER-encoded certificates in plaintext - no per-certificate encryption |
| Integrity protection | Keyed SHA-1 digest over the entire store content, derived from the store password; detects both tampering and a wrong password |
| Entry types | Two types: KeyEntry (encrypted private key + certificate chain) and TrustedCertEntry (bare certificate) |
| Entry addressing | Each entry is identified by a unique string alias; aliases are case-insensitive within a store |
| MIME type | application/x-java-keystore (Java-specific); falls back to application/octet-stream for generic handling |
| Typical file size | 1 KB - 50 KB for a few keys and certificates; up to several MB for large trust stores such as cacerts |
| Primary management tool | JDK keytool command-line utility; graphical alternative is KeyStore Explorer |
| Platform scope | Portable across any OS with a JRE or JDK, but the format is Java-specific and not interoperable with OpenSSL or other non-Java PKI tools |
| Deprecation status | Deprecated by Oracle since JDK 9 (2017); PKCS#12 is now the default keystore type and keytool warns on every JKS store opened |
| Stronger Sun variant | JCEKS (magic 0xCECECECE) - a Sun extension with Triple-DES key wrapping; still Java-only |
| System trust store | The JDK cacerts file shipped with every JRE has historically been a JKS keystore holding hundreds of root CA certificates |
| Released | 1990s, with the Java security architecture (Java Cryptography Architecture) |
| Latest version | JKS format unchanged; deprecated in favor of PKCS#12 (default keystore type since JDK 9, 2017) |
| Specification | docs.oracle.com |
JKS conversions
Community Q&A
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