Free GenCAD viewer (.cad, .gcd)

Is your .cad file a GenCAD file?

The .cad extension is used by several unrelated programs, including general drawing software and a Samsung boardview format. A GenCAD file is text and starts with a $HEADER section that contains the line GENCAD 1.4. Open it in a text editor without saving to check.

You do not have to know in advance. TRACE identifies a file by its content, not by its extension. It tells a GenCAD .cad apart from a Samsung CAD .cad (selected real exports checked), and it says so when a file matches none of its formats.

What TRACE reads from a GenCAD 1.4 file

• Sections from $HEADER to $SIGNALS: parts, pins, pads, nets (signals) and the board outline. GenCAD is validated with real files.
• Units from the UNITS header: MM, INCH, THOU or MIL, and USER units (25.4 divided by the given divisor).
• Sides: LAYER TOP and BOTTOM; SHAPE MIRRORX, MIRRORY, MIRRORXY and FLIP select the padstack layers.
• Pads: ROUND and RECTANGLE pads keep their exact size. Other pad shapes are drawn as their bounding rectangle.
• Outline: the outer closed board contour. Cutouts are reported as a warning, not drawn.

Limits

• Only GenCAD 1.4. A file that declares another version is refused with a message that GenCAD 1.4 is required.
• Before any pin is created, TRACE checks the expanded size of the board: up to 250,000 components, 1,000,000 pins and 8,000,000 placed outline, body and pad-corner points.
• A file may hold up to 8,000,000 lines within the 64 MiB file limit.
• TRACE does not edit GenCAD files and does not convert them to other formats.

How to get a GenCAD file

Many PCB design tools can export GenCAD 1.4. TRACE also reads selected native Allegro and Mentor Neutral layouts, ODB++ models and IPC-2581 exports. For unsupported variants, request a GenCAD export from the original design tool; the support table gives each reader's exact limits.

If the design comes from KiCad or EAGLE, you do not need GenCAD at all: TRACE opens KiCad boards and EAGLE boards directly, with their schematics.

Open a GenCAD file in TRACE

1. Download TRACE: a portable Windows EXE, the experimental macOS build for Apple silicon, or the experimental Linux packages (.deb and AppImage).
2. Press Ctrl+O (Cmd+O on a Mac) and choose the .cad or .gcd file, or drag it into the window.
3. Press Ctrl+F and search for a part, a value, a package or a net. Click a net to highlight all its pins and list the connected parts.
4. Switch between the top and the mirrored bottom side, rotate (R), fit the board (F) and measure between two pins (M).

Add the schematic PDF and your notes

Attach the board's schematic PDF and datasheets in the Documents tab. TRACE searches their text, and exact board references found in the text link to the parts on the board. For a scanned PDF, choose Recognize text to run bundled English OCR offline. Progress and Cancel are available; recognized words carry confidence marks and only exact, sufficiently confident board references become links.

Notes on a part or a pin keep your measured voltage or resistance. They follow the board file by its content, so renaming the file keeps them. The getting started guide shows each step.

Common questions

Is it really free?

Yes. TRACE is MIT-licensed open source, with no account and no telemetry.

Does it open other boardview formats?

Yes, see how to open a .brd file and how to open a .bvr file. Several classic boardview formats are still drafts tested with synthetic files only; the format table says which. The comparison lists other boardviewers too.

Product names are trademarks of their owners. They are used here only to identify file formats and programs; TRACE is not affiliated with any of them.

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