Compare
Comparison mode lets you import two Gerber packages and analyze the differences between them. This is useful for verifying design revisions, checking ECO changes, or auditing supplier-provided files against your source.
Creating a compare project
Compare projects are local-only — they are stored in your browser and cannot be created inside a Team. From the home page, click New Compare Project. You are prompted to import two file sets:
- Packet 1 – the reference (original) design
- Packet 2 – the revised or alternate design
Each packet can be a ZIP file or individual Gerber/drill files.
Layer matching
Gerbtrace automatically matches layers between the two packets by file name and layer type. If automatic matching produces incorrect pairings, you can manually re-match layers.
Identical file detection
Before running any visual comparison, Gerbtrace computes a SHA-256 hash of each file. Identical layers are flagged as unchanged so you can focus on the differences.
Quick comparison summary
The sidebar includes a compact change summary:
- Routing changes – changed copper, outline, drill, or inner layers
- Assembly changes – changed solder mask, silkscreen, or paste layers
- Only Packet 1 / Only Packet 2 – layers that exist only in one packet
- Matched / Identical counts – quick confidence check
Comparison modes
Side by Side
Two canvases with synchronized pan and zoom. Scrolling or panning on one side mirrors the other for direct visual comparison.
Overlay Toggle
Both versions on the same canvas, blinking between them at a configurable speed. Effective for spotting subtle geometry shifts or moved pads.
Pixel Diff
Pixel-by-pixel comparison:
- Red – pixels only in Packet 1 (removed)
- Green – pixels only in Packet 2 (added)
- Gray – identical pixels
Text Diff
Line-by-line source comparison of raw Gerber text, similar to a code diff viewer. Useful for understanding exact command-level changes.
Alignment
If the two packets use different coordinate origins, use the alignment tools:
- Pick a reference point on Packet 1 (e.g., a pad or fiducial).
- Pick the corresponding point on Packet 2.
- Gerbtrace aligns the coordinate systems.
This is especially important for pixel diff mode where small offsets produce false positives.