Open JAR files in your browser
Java code and what it needs, in one file. Open one right here to see what it is, the Java it runs on and who signed it, without running it. Nothing leaves your device.
Or drop it anywhere on this page
What you'll see
Your app opens like a folder, its files listed on the left, with a page beside them on what it is, who signed it and what it asks for.
- Its signature • Checked inside your browser
- SHA-256 • Compare it or look it up on VirusTotal
- Heads-ups • What it asks for and what runs
- Its files • Manifests open as text
About JAR
A JAR is a ZIP of compiled Java classes with META-INF/MANIFEST.MF, which names the class that starts it, the version and the other JARs it needs. Libraries often carry their Maven details in META-INF/maven/, and a fat JAR packs every library it uses inside.
A signed JAR lists each file's digest in its manifest, signs that list in a .SF file, and keeps the signature with its certificate in a .RSA, .DSA or .EC file beside it. Java checks every entry against them as it loads, so a changed class fails.
Filepeek checks the signature and every entry's digest, and says which files aren't signed. It reads the manifest, works out the Java version the classes need, and lists the JARs packed inside and the dependencies its Maven details name.
Java archive
.jar
Format
- MIME type
- application/java-archive
- Made by
- Sun Microsystems
- Released
- 1997
Inside the file
- Container
- ZIP
- Manifest
- META-INF/MANIFEST.MF
- Code
- Java class files
- Signature
- JAR signing, in META-INF
Opens in every browser
No browser opens a JAR: they download it. Filepeek opens it as a folder in Chrome, Edge, Firefox and Safari.
- YouChromeOpens through Filepeek
- YouEdgeOpens through Filepeek
- YouFirefoxOpens through Filepeek
- YouSafariOpens through Filepeek
Questions
How do I open a JAR without running it?
Drop it on this page or choose Peek a JAR. A page shows its manifest, the Java version it needs and the libraries inside, and its files are listed like a folder. Nothing runs.
Can I check a JAR's signature?
Yes. Filepeek checks the signature and its certificate, then every file's digest, and says if any file was changed or added after it was signed.
How do I look up a JAR on VirusTotal?
Filepeek works out its SHA-256 inside your browser. Look up on VirusTotal opens VirusTotal's page for that hash, and only the hash goes, never the file. Compare checks it against a SHA-256, SHA-1 or MD5 you paste.
Does opening a JAR run it?
No. Filepeek only reads it: nothing in it runs and it never leaves your device.
Can I get files out of a JAR?
Yes. Pick any file on the left to open it. Its manifest and properties open as text. In Chrome and Edge on a computer, Export extracts them all into a folder.