Type “gerber viewer” into a search engine and most of the top results are websites: drag your files into the browser, see your board, done. Desktop viewers like Gerbv ask for a download and an install first. Which approach should you actually use? The answer depends on what the files are worth, how big they are, and how often you do this. This comparison works through the five differences that matter — privacy, file handling, connectivity, depth of inspection, and repeat use — and ends with a simple rule of thumb.
Privacy: where do your design files go?
This is the deciding factor for most professional work. An online viewer can only show you your board by receiving your files: you upload the complete fabrication data for the design to a third-party server, where it is processed — and, depending on the service’s policies, possibly stored, logged or retained. For an open-source hobby board, that may be an acceptable trade. For a client’s design, an unreleased commercial product, or anything under a confidentiality obligation, uploading the manufacturing files is a disclosure — the Gerber set is, in effect, the recipe for the board. A desktop viewer never raises the question. Gerbv runs entirely on your machine; the files stay exactly where they started, and there is no account, no terms-of-service change and no server breach that can expose them. If the design is proprietary, this point alone settles the comparison.
File size and the whole set, not one file
A real board is not one file. It is a set — several copper, mask, silkscreen and paste layers, plus a drill file — that only makes sense inspected together, in registration. Web viewers impose upload limits and browser-side processing limits that vary by service and are rarely generous; large, dense boards with big copper pours can render slowly or fail outright in a browser tab, and uploading a multi-file set file-by-file is fiddly. A desktop application reads the set from your disk at full speed, stacks the layers, and lets you toggle, recolour and overlay them without re-uploading anything when you change your mind about one layer. The difference is minor for a tiny two-layer board and decisive for a complex one you will inspect repeatedly during a design review.
Offline work and independence
Desktop software works where the work is: on a factory floor, in a lab, on a train, during an internet outage, or inside a company network that blocks file-upload sites outright — many corporate networks do exactly that, for exactly the privacy reasons above. An online viewer is unavailable in all of those situations, and it is also unavailable on the day the service is down, changes its limits, or shuts down. Installing a desktop viewer is a one-time, few-minutes task; after that, the tool is simply there, behaving the same way every time, which is what you want from an inspection step in a manufacturing workflow.
Depth: measuring, reporting and exporting
Browser viewers are optimised for the quick look, and their feature sets reflect it — some offer no measurement tools at all, which rules out verifying a hole size, a clearance or a board dimension. A desktop viewer like Gerbv is built for inspection depth: measurement on the displayed image, layer controls with transparency so you can see through the stack, and report windows summarising the Gerber and drill codes actually used in your files. Export matters too: Gerbv exports the stacked view to PNG, PDF, PS, SVG and DXF, which is how a check becomes a record you can attach to a review or send to a colleague — without sending them the design files themselves. If your “viewing” regularly turns into “verifying”, that depth is the difference between the two categories.
Repeat use changes the maths
The honest case for online viewers is a single, occasional look: a file someone sent you, on a machine that is not yours, where installing software is not an option and the design is not sensitive. There, a browser viewer is genuinely the fastest path from file to picture, and tools such as the Ucamco reference viewer also offer an authoritative rendering for odd files. But notice how quickly the balance tips as use repeats. The second or third time you upload the same growing file set, wait for processing, and work within a browser’s limits, the one-time install you skipped would already have paid for itself. Professionals who check boards weekly — or daily — standardise on a desktop viewer for the same reason they standardise on any local tool: speed, privacy and predictability, every time.
There is also a consistency argument that rarely gets mentioned. A desktop viewer renders your file the same way today, next month and on a colleague’s machine running the same release, so when two people disagree about what a layer shows, they can compare like with like. A web service can change its renderer, its limits or its interface at any time, silently — fine for a glance, unhelpful when you are trying to reproduce exactly what you approved last week.
The balanced verdict
Online viewers are fine — for a quick, non-sensitive look, on someone else’s machine, at a small file. Desktop viewers win for everything else: proprietary designs that must not be uploaded, large or multi-file boards, offline and restricted-network work, measurement and export depth, and any workflow you repeat. That is why this site documents Gerbv, a free, open-source desktop viewer for Windows, Mac and Linux: it removes the privacy question, costs nothing, and is built for inspection rather than first impressions. Read the full overview on our Gerber viewer page, weigh the alternatives in best free Gerber viewers, or get Gerbv itself from the download page.
Frequently asked questions
Is it safe to upload Gerber files to an online viewer?
It depends on the design and the service. Uploading means a third party receives your complete fabrication data, so do not upload proprietary or client work. For a non-sensitive file and a quick look, a reputable online viewer is a reasonable convenience.
Do desktop Gerber viewers cost money?
Not necessarily. Gerbv is free and open source under GPL-2.0-or-later for Windows, Mac and Linux, and KiCad’s GerbView is free as part of that suite. Commercial desktop viewers exist too, usually with free tiers.
Can an online viewer measure my board?
Some can, some cannot — at least one well-known browser viewer offers no measurement tools at all. If verifying dimensions matters, a desktop viewer such as Gerbv, with measurement, reporting and export built in, is the safer default.