Definition

Printer G-code commonly uses a semicolon for the rest of a line as a comment. CNC dialects may also use parentheses, while some controllers define special active-comment forms. Syntax therefore depends on the interpreter; text that looks harmless in one dialect may have a special meaning in another.

Slicers write feature labels, layer markers, estimated time, filament usage, profile names and thumbnails as comments. This can enrich analysis, but it is optional producer-supplied evidence. It can be absent, stale, edited or formatted differently, and it does not prove the printer's live firmware, material or state.

What matters in practice

Commands and annotations differ

Removing an ordinary comment should not change printer motion, while removing a command does.

Formats are producer-specific

TYPE, FEATURE, layer and filament fields vary across slicers and versions.

Useful but not authoritative

Metadata can support estimates and labels without proving runtime hardware or safety.

Example in G-code

Feature and usage annotations

; generated by ExampleSlicer
;TYPE:WALL-OUTER
G1 X40 Y20 E1.2
; filament used [mm] = 1234

The semicolon lines name a producer, a feature and declared usage; only G1 commands the visible move.

What this viewer can show

In this viewer

The viewer parses tested comment signatures for move types and declared estimates, then keeps calculated and declared evidence separate. Unknown comments remain source text; metadata never overrides explicit motion without a documented rule.

Primary sources

This explanation uses firmware documentation and details visible in G-code. Your printer's settings still determine what the machine does.