KiCad "Track width" DRC error: track narrower than the rule
KiCad design rule check (PCB) message: Track width (track_width in kicad-cli reports).
What it means
A track is narrower (or wider) than the track width rule that applies to it. The limit comes from the board minimum, the net class or a custom rule. Widen the track, or fix the rule if the limit is wrong for that net.
Common causes
- Tracks drawn with a custom width smaller than the board minimum, often to squeeze between fine-pitch pads.
- A custom rule with a minimum or maximum width for certain nets (for example power nets that must be wide).
- A net class changed after routing.
How to fix it
- Select the tracks and use Edit → Edit Track & Via Properties to set the width, or "Use net class values".
- Where a track must neck down at a fine-pitch pad, write a custom rule that allows the narrower width only inside that footprint's area.
- Use the trace width calculator to size current-carrying tracks before you set the net class width.
Where the setting lives
Board Setup → Design Rules → Constraints → Minimum track width; Board Setup → Net Classes; Board Setup → Custom Rules.
What fabs need
JLCPCB lists 0.1 mm (1–2 layers) and 0.09 mm (4+ layers) as standard minimum trace width; PCBWay lists 0.1 mm.
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Checked against KiCad 10's source and documentation. Last reviewed 2026-11-07.
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