Global label not connected anywhere else in the schematic

Diagnostic signature

Global label not connected anywhere else in the schematic

KiCad's Electrical Rules Checker (ERC) reports this warning when a global label appears only once in the entire schematic hierarchy, indicating it fails to form an inter-sheet connection.

What it means

A global label in KiCad establishes a logical, inter-sheet electrical connection for a specific net [1]. Because its fundamental purpose is to connect points globally across the hierarchical design, it is inherently required to be present at least twice to form a complete, valid link [1, 2]. When the Electrical Rules Checker (ERC) emits this diagnostic, it has detected exactly one instance of a global label with a specific name in the entire project [1]. This indicates that the label is acting as an orphaned terminating point rather than a valid cross-sheet link, failing to establish the intended multi-pin global connection [1].

Why it happens

This warning usually surfaces due to data entry errors, naming mismatches, or incomplete schematic capture [2]. The most frequent cause is a typographical discrepancy between intended label pairs, such as inconsistently using dashes versus underscores (e.g., VCC-PIC versus VCC_PIC) or differing capitalization [2]. It also happens when a designer deletes one end of a global connection but forgets to remove the remaining obsolete label, or simply overlooks placing the required matching counterpart on the target hierarchical sheet. Occasionally, it is triggered by incorrectly placing a global label when a local label was sufficient for a single-sheet connection.

Minimal reproduction

(kicad_sch (version 20211123) (generator eeschema)
  (paper "A4")
  (lib_symbols
    (symbol "Device:R"
      (pin passive line (at 0 0 0) (length 2.54)
        (name "~" (effects (font (size 1.27 1.27))))
        (number "1" (effects (font (size 1.27 1.27))))
      )
    )
  )
  (symbol (lib_id "Device:R") (at 100 100 0) (unit 1)
    (in_bom yes) (on_board yes)
    (uuid "00000000-0000-0000-0000-000000000001")
  )
  (wire (pts (xy 100 100) (xy 110 100))
    (stroke (width 0) (type default))
    (uuid "00000000-0000-0000-0000-000000000002")
  )
  (global_label "ORPHAN_NET" (shape input) (at 110 100 0) (fields_autoplaced)
    (effects (font (size 1.27 1.27)) (justify left))
    (uuid "00000000-0000-0000-0000-000000000003")
  )
)

How to fix it

Review the intended connectivity for the flagged net. Either correct typographical errors to match its target counterpart, add the missing label on the destination sheet, or convert it to a local label.

```S-expression
(kicad_sch (version 20211123) (generator eeschema)
  (paper "A4")
  (lib_symbols
    (symbol "Device:R"
      (pin passive line (at 0 0 0) (length 2.54)
        (name "~" (effects (font (size 1.27 1.27))))
        (number "1" (effects (font (size 1.27 1.27))))
      )
    )
  )
  (symbol (lib_id "Device:R") (at 100 100 0) (unit 1)
    (in_bom yes) (on_board yes)
    (uuid "00000000-0000-0000-0000-000000000001")
  )
  (wire (pts (xy 100 100) (xy 110 100))
    (stroke (width 0) (type default))
    (uuid "00000000-0000-0000-0000-000000000002")
  )
  (global_label "ORPHAN_NET" (shape input) (at 110 100 0) (fields_autoplaced)
    (effects (font (size 1.27 1.27)) (justify left))
    (uuid "00000000-0000-0000-0000-000000000003")
  )
  (symbol (lib_id "Device:R") (at 100 150 0) (unit 1)
    (in_bom yes) (on_board yes)
    (uuid "00000000-0000-0000-0000-000000000004")
  )
  (wire (pts (xy 100 150) (xy 110 150))
    (stroke (width 0) (type default))
    (uuid "00000000-0000-0000-0000-000000000005")
  )
  (global_label "ORPHAN_NET" (shape input) (at 110 150 0) (fields_autoplaced)
    (effects (font (size 1.27 1.27)) (justify left))
    (uuid "00000000-0000-0000-0000-000000000006")
  )
)
```

Step 1

• Examine the schematic hierarchy to find the intended destination sheet for the flagged global net.

Step 2

• Check for typographical discrepancies. If a misspelled label exists on another sheet, edit its text properties to exactly match the target net name, ensuring capitalization and punctuation are identical.

Step 3

• If the signal is genuinely meant to propagate to another sheet but the corresponding label is missing, place a new global label with the identical name on the destination sheet.

Step 4

• If the net is strictly contained within the current sheet and requires no cross-sheet routing, delete the global label and replace it with a standard local label.

Upstream references

Schematic Editor | 9.0 | English: List of ERC checks

Schematic ERC doesn't detect single global label net (#15820)