What this error means
A no-connect flag (the X placed with the Q key) only means something when it sits on a pin. For each flag, ERC collects everything on the flag's resolved net: symbol pins (a stack of pins at one point counts once) and labels of any kind — local, global, or hierarchical. If both sets come back empty, the flag marks nothing, and ERC reports the flag itself.
Three placements are accepted without a warning: a flag on a pin whose electrical type is Unconnected, a flag directly on a hierarchical sheet pin or hierarchical label, and — in KiCad 10 only — a flag at the end of a bare wire stub whose sole link to the schematic is a hierarchical sheet pin or label.
The flag is electrically inert either way; it never changes the netlist. The warning exists because a flag that marks nothing usually means some pin is sitting unmarked, reporting its own violation.
Common causes
1. The symbol moved or was deleted; its flags stayed
A no-connect flag is its own schematic item anchored to a position, not a property of the pin under it. Move a symbol to make room, or delete and replace it, and every flag it had stays floating at the old pin locations. This is the common case.
2. The flag never landed on the pin's connection point
The flag has to sit exactly on the small circle at the free end of the pin. Dropped on the pin's body, its name, or a point the pin end doesn't actually occupy (typical when the symbol itself sits off the 50 mil grid), it attaches to nothing — and the pin it was meant to cover reports "Pin not connected" separately.
3. You flagged an unused sheet pin through a wire stub in KiCad 9
In 9.0, a no-connect at the end of a short wire off a hierarchical sheet pin still warns; only a flag placed directly on the sheet pin is accepted. KiCad 10 accepts the stub form too.
How to fix it
Delete the stray flag
- Click the flagged X (Esc first to get the selection tool) and press Delete.
- Re-run ERC (Inspect → Electrical Rules Checker); the flag's marker goes with it.
Use when: The flag is leftover clutter from an earlier edit. Before deleting, glance around for a pin nearby that was supposed to carry it.
Move the flag onto the pin end
- Zoom in until you can see the connection point — the small circle at the free end of the pin.
- Drag the flag onto that point; on the default 50 mil grid it snaps.
- If it will not land, the symbol is off grid: select it, right-click → Align Items to Grid, then place the flag.
- Re-run ERC and confirm the pin's own "Pin not connected" violation cleared with it.
Use when: You meant to mark a real pin as intentionally unconnected and the flag missed it.
In KiCad 9, flag the sheet pin itself
- Delete the wire stub between the hierarchical sheet pin and the flag.
- Place the no-connect directly on the sheet pin's connection point.
Use when: An unused hierarchical sheet pin is flagged through a short wire and you are on 9.0. On 10.0 the stub form is accepted and nothing needs to change.
When it’s safe to exclude
Excluding is defensible here in a way it rarely is: a dangling flag has no electrical effect, so this warning is about hygiene, not correctness. But the fix is one click on one item, and the warning's real value is the pattern it exposes — a dangling flag next to a "Pin not connected" error means you believed a pin was covered when it is not. Delete the flag rather than excluding the marker (right-click → Exclude); if you want the whole class quieter, downgrade it in Schematic Setup → Electrical Rules → Violation Severity, knowing what it would have said.
Gotchas
- No-connect flags do not travel with the symbol they cover. Every move or delete-and-replace of a symbol quietly orphans its flags, which is why this warning tends to show up in batches after a cleanup pass.
- This warning and "Pin not connected" often arrive as a pair pointing at the same spot: the flag missed the pin, so the flag dangles and the pin goes uncovered. Fixing the placement clears both.
- Pins with electrical type Unconnected need no flag — the symbol author already declared them unconnected. A flag on one is accepted silently, but it is doing nothing.
Version notes
- KiCad 10.0: A flag at the end of a bare wire stub off a hierarchical sheet pin or label no longer warns; 9.0 accepts the flag only when placed directly on the sheet pin.
Minimal reproduction
Press Q and drop a no-connect flag on empty grid space — or delete a symbol that had flagged pins and leave the flags behind — then run ERC:
[no_connect_dangling]: Unconnected "no connection" flag
; warning
@(116.84 mm, 88.90 mm): No Connect
The checked-in file data/erc/samples/no_connect_dangling.kicad_sch
reproduces this with two embedded one-pin symbols wired pin to pin (a
quiet, valid net) and one no-connect flag floating above the wire. The
two lib_symbol_issues warnings about the missing repro library are
an artifact of the self-contained file, not part of this error.
Deleting the no_connect element drops the report to those two
warnings, which is fix #1 in miniature. Verified with kicad-cli sch erc under 9.0.1 and 10.0.6.
Related errors
- A pin with a "no connection" flag is connected
- Pin not connected
- Wires not connected to anything
- Symbol pin or wire end off connection grid
FAQ
Does a dangling no-connect flag actually affect the netlist?
No. A no-connect flag only suppresses unconnected-pin checks on the pin it sits on; one sitting on empty space changes nothing in the netlist or the board. The risk is bookkeeping: a pin somewhere may be missing the flag you thought you placed.
Why won't the no-connect flag attach to my pin?
The flag has to land exactly on the pin's connection point, the small circle at the pin's free end. Use the default 50 mil grid, and if the circle sits between grid points, the symbol itself is off grid — select it and use right-click → Align Items to Grid, then place the flag on the pin end.
I put a no-connect on an unused hierarchical sheet pin and ERC still complains. Why?
KiCad 9 accepts the flag only when it sits directly on the sheet pin; a flag at the end of a short wire stub off the pin warns until KiCad 10, which accepts the stub form. If it still warns on 10, the stub has picked up a label or a pin, which cancels the exemption.