How we rank online Gerber viewers

A Gerber viewer has one job: show you, before you pay for boards, what a manufacturer will build from your files. So we rank viewers on what helps you catch a problem, in the order it matters, and we only use facts you can check yourself on each tool's own site.

The six criteria

1. 1. File supportWhich formats does it open: Gerber RS-274X, Gerber X2, Excellon and other drill formats, ZIP packages, other CAD or manufacturing formats?
   How we check: We read the formats the tool's own page or documentation lists, and note where a format is only partly supported or labelled beta.
2. 2. Layer accuracyDoes it draw every layer as the data says, assign each file to the right layer, and let you look at layers one at a time?
   How we check: We note how the tool builds its picture (from the Gerbers, from the design source, or both) and anything its maker says about accuracy or known gaps.
3. 3. Drill and outline handlingDoes it open drill files alongside the copper, line the holes up with the pads, and show the board outline clearly?
   How we check: We check which drill formats are listed as supported and whether the outline and holes appear in the board view.
4. 4. Privacy of uploadsWhere do your files go? Are they processed in your browser, kept on a server, shared by link, or deleted at the end of the session?
   How we check: We quote what the tool's privacy policy or viewer page says about where files are processed and how long they are kept. Where it says nothing, we say so.
5. 5. Measuring toolsCan you measure distances, clearances and board size, and inspect individual objects?
   How we check: We list measuring and inspection tools the tool documents or shows in its own interface.
6. 6. Source files as wellCan the same tool open the design source (a KiCad project, Altium or EAGLE files), so you can see the schematic, nets and parts behind the Gerbers?
   How we check: We list the design formats the tool opens, and whether it shows schematic, PCB, 3D and bill of materials.

How the order is decided

What you can check depends on what you have, so the ranking starts from your situation. Every tool goes through the same three steps, worked out from its marks alone.

1. If you have the design source (a KiCad project, or Altium or EAGLE files): tools that open source files (marked Yes or Partly for source files) are ordered by that mark first, then by the other five criteria in weight order.
2. If you only have Gerbers: tools whose own pages say they open Gerber files are ordered by the first five criteria in weight order. Where two tie, the one that documents more checks on Gerber data beyond viewing (a syntax checker, attribute display, set comparison) goes first.
3. The overall list takes each tool's best position in either list. The top pick for the design-source list comes first, then the top pick for Gerbers only, and any other ties are broken by the marks in weight order.

The weight order is the order of the criteria above:

1. Can it show your board correctly? File support, layer accuracy, and drill and outline handling come first. A viewer that can't open your drill file, or draws the outline wrongly, can't help you check anything.
2. Can you trust it with the files? Your Gerbers are a full copy of the board's copper. A viewer that keeps files in your browser, deletes them at the end of the session, or keeps them private scores higher than one that says nothing.
3. Can you check details? Measuring distances, clearances and board size, and inspecting individual objects, turn a picture into a check.
4. Can it open the design as well? A viewer that also opens the source, such as a KiCad project, shows the schematic, nets and parts behind the copper. That answers questions Gerbers can't. See Gerber files versus design source files.

Each viewer's card and page shows its place in both situation lists, so you can follow the one that matches your files.

How each criterion is marked

We don't give star ratings or scores out of ten, and we don't quote user reviews or usage numbers we can't check. Prices are listed only where the tool publishes them; where it doesn't, the page says where to look.

Same rule for every tool

Every viewer here, including BoardRepo, is judged on the same six questions, with the same marks and the same three steps. BoardRepo is first in the design-source list: it and KiCanvas are the only tools marked Yes for source files, and BoardRepo's marks are higher on drill and outline handling, upload privacy and measuring. That puts it first overall. It isn't in the Gerbers-only list, because its own pages don't say it opens loose Gerber files. Its limits are stated beside it: it is not a fabrication service, and some uploads do not render fully, which is why its layer accuracy is marked Partly. With Gerbers alone, the Gerbers-only list starts with Ucamco's Reference Gerber Viewer.

Every viewer side by side

Keeping it current

Each viewer's page lists the sources its claims come from, and the date at the top of this page is when the ranking was last reviewed against them. If a tool has changed, send a correction with a link we can check.