What is the FZ file format?
A .fz file is a Fritzing Sketch File - the native project format of Fritzing, an open-source electronics design application aimed at prototypers and hobbyists. The file stores a complete circuit sketch in plain-text XML (UTF-8), describing component placement and wiring across three parallel design views: breadboard, schematic, and PCB layout.
Internally, the document uses a <module> root element carrying a fritzingVersion attribute that records which version of the application last saved it. Part instances appear under <instances>, each containing per-view geometry, connection data, and component properties. Because .fz references parts by library ID rather than embedding them, a file may not render correctly without the matching Fritzing parts library installed.
For sharing, Fritzing wraps the .fz together with any custom parts (.fzp definitions and .svg visuals) and Arduino sketches (.ino) into a .fzz ZIP archive - the recommended distribution format. The .fz itself carries no compression or encryption and typically ranges from a few kilobytes to a few hundred kilobytes, depending on circuit complexity.
The format is supported on Windows, macOS, and Linux through the official Fritzing application. Its plain-text XML structure also allows inspection or manual editing in any standard text editor.
Security & safety
RISK: LOWA .fz is a plain XML document with no executable code, so it is safe to open and inspect. The only practical hazard is that a Fritzing sketch can reference an attached Arduino sketch (.ino) - review any bundled code before flashing it to hardware. Download Fritzing only from fritzing.org or its official GitHub; some third-party 'fz openers' are adware bundles.
Format details
in a nutshell- Casio synthesizer voice data - Older .fz files were sample/voice banks for Casio FZ-1/FZ-10M samplers - unrelated to Fritzing.
- FileWrangler / Frozen-Bubble level data - Legacy uses of .fz by FileWrangler compressed files and the Frozen Bubble game's level format.
Programs that open FZ files
Windows2 apps
Fritzing
Paid File → Open and select the .fz. Fritzing is now a small paid download (pay-what-you-want, from €8) but source is free to build. 
Notepad / any text editor
Open-source Open the .fz to read its XML (parts, connections) - inspection only, no rendering. 
macOS1 app
Linux1 app
Fritzing
Paid Install from fritzing.org or distro repos and open the .fz; source is on GitHub to compile free. Technical details
deep spec| Format type | Plain-text XML (UTF-8), uncompressed |
| MIME type | application/x-fritzing-fz |
| File signature | No binary magic bytes; file begins with the XML declaration <?xml … ?> followed by a <module> root element |
| Root XML element | <module> carrying a fritzingVersion attribute that records the Fritzing app version which last saved the file |
| Design views encoded | Three simultaneous views per circuit - breadboard, schematic, and PCB layout - each stored within every part instance |
| Part referencing model | Parts referenced by library ID only; custom part definitions are not embedded inside the .fz file |
| Instance data structure | Each <instance> holds per-view geometry (x/y position, rotation), connection wire data, and component properties |
| Compression | None - the .fz is uncompressed XML; its distributable counterpart .fzz wraps it inside a ZIP archive |
| Typical file size | A few KB to a few hundred KB depending on circuit complexity (geometry and references only; part data not embedded) |
| Board and view settings | Stores board geometry and per-view display settings such as grid size, zoom level, and pan offsets alongside part instances |
| Parts library dependency | File may fail to render correctly without the Fritzing parts library containing the part IDs referenced in the sketch |
| Shareable packaging | .fzz bundles the .fz with custom .fzp part files and .ino Arduino code for complete, self-contained portability |
| Relationship to .fzz | The .fz is the inner document inside every .fzz archive; .fzz carries ZIP magic bytes (50 4B 03 04), distinguishing it from the plain-XML .fz |
| Supported platforms | Windows, macOS, Linux - via the official Fritzing application or any XML-capable text editor for inspection |
| Released | 2009 (Fritzing 0.x; .fz is the early uncompressed sketch format) |
| Latest version | Sketch format tracked by the fritzingVersion attribute (Fritzing 1.0.x as of 2024) |
| Open standard | Yes · royalty-free |
| Specification | github.com |
FZ conversions
Community Q&A
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