This comparison exists mostly to prevent a category error. Gerbv and FlatCAM both open Gerber files, and lists of “Gerber software” shelve them side by side — but they do different jobs. Gerbv is a viewer: it exists so you can inspect fabrication files before they are manufactured. FlatCAM is a Gerber-to-G-code converter for CNC PCB milling: it exists so a milling machine can cut a board out of copper-clad stock by isolation routing. One answers “is this file correct?”, the other answers “machine, cut here”. Many makers legitimately use both, in sequence. If you found this page while shopping for a viewer, start with the Gerber viewer hub and the best free Gerber viewers roundup; if you mill boards at home, read on for where each tool sits in your process.
Two different outputs
Follow the outputs and the difference is unmistakable. Gerbv’s outputs are for human eyes and human correspondence: the stacked layer view itself, measurements taken on the displayed image, statistics reports about the Gerber and drill codes in use, and exports to PNG, PDF, PS, SVG and DXF that you can attach to an email or a design review. FlatCAM’s output is for a machine: G-code toolpaths that a CNC mill follows to isolate traces and cut the board free. A viewer that produced toolpaths would be a hazard; a converter you could not visually verify against the original would be a different hazard. Each tool is shaped by its output.
Where each belongs in the workflow
If you order boards from a fab house, FlatCAM has no role in your week — the fab does its own manufacturing preparation — and Gerbv is the pre-order check: open the exact ZIP, stack the layers, confirm drills register with pads, measure the outline, then send it. The pre-order checklist is written for exactly that pass. If you mill prototypes at home, the order flips: FlatCAM is your production tool, and Gerbv becomes its proofreader. Viewing the Gerber set in an independent program before converting catches the classic milling-day disasters while they are still free to fix — a mirrored bottom layer, drills in the wrong unit, a missing outline, an extra board revision mixed into the folder. Converting a bad file produces a precisely machined bad board.
What Gerbv does and does not do
Gerbv is free, open source (GPL-2.0-or-later), and runs on Windows, macOS and Linux — get it from the download page. It views Gerber RS-274X layers, Excellon drill files and CSV pick-and-place files stacked together, works entirely offline, and needs no account. Its limits are worth stating because they define the partnership: it generates no G-code and drives no machine, it has no DRC, it renders in 2D only, and it does not read legacy RS-274D files. FlatCAM, for its part, is a converter with a viewing surface for its own work — its centre of gravity is toolpaths, not inspection reports, measurement-driven verification or documentation export.
Can one replace the other?
No, in either direction. Using FlatCAM as your only Gerber viewer means checking files inside the tool whose job is to transform them — the same single-tool blind spot that makes independent verification valuable everywhere else in this craft. Using Gerbv as a milling tool is simply impossible; it will show you a beautiful, correct board and then stop, leaving the copper uncut. The tools compose instead of competing: design, export, inspect in Gerbv, then either order from a fab or convert in FlatCAM and mill. The inspection step is cheap; both manufacturing routes are more expensive than the check that precedes them.
Cost and platforms
Money does not separate these two: both are free, and FlatCAM — like Gerbv — belongs to the open-source side of the bench. Gerbv runs on Windows, macOS and Linux, so the inspection half of the partnership can live on whatever machine you design on, while the milling half naturally lives wherever the CNC machine is driven from. That split is another reason the two tools compose so well in practice: check the files at your desk, on your main computer, then carry the verified set to the workshop machine for conversion — the files the mill receives are the files a human already approved.
Verdict: a sequence, not a contest
Choose Gerbv when the task is seeing, checking and documenting Gerber files. Choose FlatCAM when the task is turning those files into G-code for your own CNC mill. Choose both — in that order — if you mill at home and would like the board you designed to be the board the machine cuts.
Frequently asked questions
Can Gerbv create G-code for my CNC mill?
No. Gerbv is a viewer — it displays, measures and reports on Gerber, drill and pick-and-place files, and exports images and DXF. It produces no toolpaths. Converting Gerber files to G-code for isolation milling is FlatCAM’s job.
Can FlatCAM replace a Gerber viewer?
Not comfortably. FlatCAM’s purpose is conversion to G-code; it centres on toolpaths rather than inspection tooling like measurement-driven verification, code statistics and documentation export. Checking the set in a dedicated viewer such as Gerbv before converting is the safer sequence.
Do I need either tool if I order boards from a fab?
You do not need FlatCAM — the fab prepares its own manufacturing data. A viewer is still worthwhile: a ten-minute check of the ZIP in Gerbv, drills against pads and outline measured, catches errors while they cost nothing.