What's the difference between Excellon and Gerber?

Gerber describes the copper, mask, silkscreen and paste artwork — everything that's painted onto the PCB. Excellon describes the drill bit, hole positions and route paths the CNC machine has to perform. They travel together as a fabrication package.

What units are the diameters in?

Excellon files declare their units inline (M71 = metric, M72 = inch, or an explicit METRIC / INCH header). We respect whatever the file says and let you toggle the displayed table between millimetres and inches.

Where do slot routes show up?

Excellon `G85` slot moves are rendered as elongated holes in the SVG. They count toward the hit total but you'll see the slot shape in the drill map, not just a point.

I have a whole fabrication package — should I use this viewer?

For a single .drl / .xln file, yes. If you have a zipped fab folder containing copper, mask, outline and drill files, open it in the Gerber viewer instead — that composites the drill file on top of the board render.

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Open Excellon files

PCB drill/route files with tool table and hit map.

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About Excellon

PCB drill/route files with tool table and hit map.

Excellon files describe the drill and route operations a CNC machine performs on a fabricated PCB. Each file starts with a tool table (which size of bit corresponds to which tool number) followed by a sequence of X/Y hits. We parse the header to surface the tool table with diameters and hit counts, then render the actual hole positions as an SVG so you can sanity-check that every footprint you expected is being drilled at the right place.

FAQ

What's the difference between Excellon and Gerber?: Gerber describes the copper, mask, silkscreen and paste artwork — everything that's painted onto the PCB. Excellon describes the drill bit, hole positions and route paths the CNC machine has to perform. They travel together as a fabrication package.
What units are the diameters in?: Excellon files declare their units inline (M71 = metric, M72 = inch, or an explicit METRIC / INCH header). We respect whatever the file says and let you toggle the displayed table between millimetres and inches.
Where do slot routes show up?: Excellon `G85` slot moves are rendered as elongated holes in the SVG. They count toward the hit total but you'll see the slot shape in the drill map, not just a point.
I have a whole fabrication package — should I use this viewer?: For a single .drl / .xln file, yes. If you have a zipped fab folder containing copper, mask, outline and drill files, open it in the Gerber viewer instead — that composites the drill file on top of the board render.

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