Update PCB from Schematic changes trace widths?

Hi - I’m a relatively new user of KiCAD, using 7.0.8. I’m working on my first non-trivial project - 4 layer board, a few hundred components, diff pairs, etc. Previous employer had me using Altium Designer (10), now I’m learning KiCAD.

I’ve run across something that I don’t understand and didn’t find in docs or forum posts; I suspect it’s been addressed, but at the moment I’m baffled, and hope someone recognizes what I’m doing wrong that causes the issue.

With design nearing completion, I made some some changes to the schematic that required Update PCB from Schematic. Before the update I had to fix a duplicate designator that got flagged - I did not reannotate the schematic using the dialog, just changed one of the designators to an unused value (on schematic and PCB) to fix the issue, then was allowed to update PCB from Schematic. Yay, no errors or warnings, but when the PCB updated it changed every trace on the board to my default trace width. I had updated the board several times from schematic early in the process, and it had not changed any trace widths…
Undo wouldn’t undo the changes. So I now seem to have only unpleasant choices, I can use a backup and lose hours of work, or I can manually update a significant percentage of my trace-widths manually. I’d sure like to figure out what I might have done that caused the mass-change in track widths.
What are the possibilities? I’m fairly sure that Update PCB from Schematic was the last operation done before the widths changed but it could have been something else… accidentally hit a keyboard shortcut (oof), or something else that I just haven’t learned yet in KiCAD.
As a new forum user, I can’t post anything more than text yet. Any constructive suggestions would be appreciated!


What you do can depend on what you did and what you want to do…

If ALL the Tracks on a particular layer are to be changed to the same width’s:

Hide all the other layers it makes selection easier) then, window-box select all the Tracks, Right-Click>Properties> set the desired widths.

If trouble selecting them, do them in smaller groups. Practice on a couple of them.

If the Properties does not list in the pop-up when right-click, it must have also grabbed a non-track item (such as a hidden anchor point or Pad - SEE the Red Crosses in screenshot below). You can Shift and select the track(s), too…

If you have Track widths defined in the Track’s panel, you can select them in the same properties panel.

And, if wanting different Track widths, select the one’s you want to change to perticular width…

Below shows three items that prohibit Properties from listing when selecting mixed items)

I have never experienced a situation where Update PCB from Schematic changed the width of tracks already on the PCB. KiCad does have a bunch of options to change the track width of existing tracks, but KiCad only does so when it it told to do so. Using Update PCB from Schematic often is also a normal workflow. If this action triggered the track width change, then I suspect it is a bug.

Thank you, BlackCoffee, your suggestions will certainly help me get my track widths reset to appropriate values.

Thank you Paulvdh - I may indeed have done something else on the accidental or dumb side. I just don’t know what. I will read through docs on the various ways to change the width of existing tracks.
Prior to the minor schematic changes (which prompted the upodate PCB from Schizmonic) I had been using Net Inspector to verify connections to my ground/earth/power planes. There’s no way i could have missed the trace width changes during that process. Whatever it was, there was no warning like “are you sure you want to change every non-default track width in your project, on four layers of the PCB to 0.2mm?”
I remain baffled, but at least I have some reading to do - maybe something will ring a bell.


What is your definition of “my default trace width”?

The usual workflow is to set up a few net classes, and use the parameters of those net classes for the tracks.

I also had a look at: PCB Editor / Preferences / Hotkeys and did a search for track.

There is a Change Track Width, that does not have a default key, but from it’s descripton it only works on a selection.

Also, when you have a few tracks selected, the u key expands the selection to select more track segments of the already selected nets. There are some other ways too to help with selection. And once you have a selection of (only) tracks, then you can press e to edit their properties, and that menu also has several options for changing the with of the selected tracks.

The only option I know to change the width of all tracks (without selecting them first) is with PCB Editor / Edit Track and Via Properties

Well I thought I had set Board Setup/ design rules / netclasses, Default to a track width of 0.2mm (because I have 300 coonnector-pads on my board that require 0.2mm or smaller tracks. But when i look there now, it is still set to the program default of 0.25mm.
The only place I’ve found 0.2mm in my setup in design rules / Pre-defined sizes.
It is one of the track widths that I can quickly select on the fly with keyboard shortcuts W and shift-W. I wonder if I hit some keyboard shortcut by accident. Or if my cat walked on my keyboard again…

These screenshots may help

Click to setup the widths…

Hover the mouse for this info…

Set the widths
Screen Shot 2023-11-28 at 10.29.19

good timing BlackCoffee - I just looked up how to use netclass controlled sizes and widths. I used similar features in AD10, but it’s been a few years, and the UI is WAY different. Still getting used to what KiCAD can and cannot do. (And seemingly does on its own - though I know it had to be something that I somehow did, in actuality.


You have promoted yourself, in this forum, to basic level by spending time reading posts. You are now able to post as you wish :smiley:

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I don’t think I know of a mechanism that would cause your trace widths to change just by updating the PCB from schematic.

Can you try updating to 7.0.9 and check if it still happens in that version? If so, it might be worth a bug report if you can attach the project (check the box to make it a confidential issue if the project needs to be kept off the public bug tracker)

I understand that it happened once and no one knows how to repeat it. So I don’t expect it is possible to check if it still happens.

If it happens again I will try to establish what immediately precedes the issue, and if it’s not an ID10T interface issue, it will submit a bug report, for sure. Thank you all for your input. I’m now being less lazy about regular cross-updating, and need to read about using the rescue saves. Thank you all for your help.

KiCad also makes automatic backups in the [Project]-backups directory. (I should have mentioned that earlier).

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