OpenAnyFile
What is a .jnlp file?
Java Web Start Launcher is a source code format developed by Sun Microsystems, first released in 2001. It is usually created by Enterprise Java apps, server consoles.
XML telling Java Web Start what to download and run. Removed from Java 11; OpenWebStart can still launch these.
File details
| Full name | Java Web Start Launcher |
|---|---|
| Category | Code |
| MIME type | application/x-java-jnlp-file |
| Signature (magic bytes) | 3C 3F 78 6D 6C (<?xml) |
| Developer | Sun Microsystems |
| Introduced | 2001 |
| Opens with | Code viewer |
| Uploaded? | No — read locally in your browser |
How to open a .jnlp file
OpenAnyFile routes .jnlp files to its code viewer, which shows the source with syntax highlighting.
- Drop your .jnlp file on the box above, click it to choose the file, or paste it with Ctrl+V.
- The real format is detected from the file's first bytes — not just its name.
- The file opens in the code viewer.
- Use fullscreen for a closer look, check its checksums, or download it back unchanged.
What works — and what does not
Works
Viewing and inspecting: the source with syntax highlighting. Size, type, signature and checksums are always shown.
Does not work
Editing and saving back. OpenAnyFile is a viewer, not an editor — for changes you still need the original app.
Is it safe to open a .jnlp file online?
Here, yes — because nothing is uploaded. Most "online viewers" send your file to their server. OpenAnyFile reads it with your browser's File API and decodes it on your own device, so there is no copy anywhere else. You can check: open your browser's network tab while opening a file — no upload appears.
Questions about .jnlp files
Can I open a .jnlp file without installing software?
Yes. OpenAnyFile opens .jnlp files in your browser using its code viewer. You get the source with syntax highlighting, with nothing installed and no account.
How do I know a file is really a .jnlp file?
Check its first bytes instead of its name. A genuine JNLP file begins with 3C 3F 78 6D 6C (<?xml). OpenAnyFile shows the detected type, so a renamed file is easy to spot.
Is my .jnlp file uploaded anywhere?
No. The file is read locally by your browser and never sent to a server — it even works offline once the page has loaded.
Does it work on phones?
Yes — on Android and iPhone, in any modern browser. You can also install OpenAnyFile as an app.
Related formats
Other formats from the same family:
Format facts checked and page updated on September 25, 2026.