OpenAnyFile
What is a .gem file?
RubyGem Package is an app package format developed by RubyGems, first released in 2004. It is usually created by gem build, RubyGems.org.
A TAR containing metadata.gz and data.tar.gz. The outer archive is browsable here.
File details
| Full name | RubyGem Package |
|---|---|
| Category | Apps & packages |
| MIME type | application/x-tar |
| Signature (magic bytes) | 75 73 74 61 72 (ustar) at offset 257 |
| Developer | RubyGems |
| Introduced | 2004 |
| Opens with | Archive browser |
| Uploaded? | No — read locally in your browser |
How to open a .gem file
OpenAnyFile routes .gem files to its archive browser, which shows the full file list as a browsable tree.
- Drop your .gem 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 archive browser.
- 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 full file list as a browsable tree. 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 .gem 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 .gem files
Can I open a .gem file without installing software?
Yes. OpenAnyFile opens .gem files in your browser using its archive browser. You get the full file list as a browsable tree, with nothing installed and no account.
How do I know a file is really a .gem file?
Check its first bytes instead of its name. A genuine GEM file begins with 75 73 74 61 72 (ustar) at offset 257. OpenAnyFile shows the detected type, so a renamed file is easy to spot.
Is my .gem 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.