Every office has that mystery: same drawing, same command, different result on two machines. Nine times out of ten, a system variable is the culprit. Here are the ones worth knowing by heart — grouped by the problem they cause.
The "why is my snapping weird" cluster
- OSNAPCOORD — controls whether keyboard coordinate input overrides running object snaps. Set to 1 (default): typed coordinates win. Set to 0: your precise keyboard entry gets hijacked by the nearest snap. Symptom: "I typed 100,100 and it went somewhere else."
- OSMODE — the numeric sum of all running snaps. Scripts that set OSMODE to 0 disable snapping entirely (useful, and the source of "my snaps vanished" panics after running someone's LISP).
- AUTOSNAP — bit-code controlling snap markers and magnet. The "magnetic pull" that helps or fights you.
The "my drawing mirrored wrong" classic
- MIRRTEXT — 1 (rare default) mirrors text physically (backwards-readable). 0 (what almost everyone wants) keeps text readable when mirroring objects. The single most common "is this a bug?" question, answered by one variable.
The "dialogs disappeared" mystery
- FILEDIA — 0 suppresses file dialogs and routes everything to the command line (a script mode nobody enables on purpose). Symptom: SAVEAS suddenly asks for the filename as typed text. Fix: FILEDIA 1.
- CMDDIA — same idea for plot dialogs. These two explain most "my AutoCAD is broken" tickets after running batch scripts.
The "dimensions drift" cluster
- DIMASSOC — 2 makes dimensions associative (they update when geometry changes). 1 = non-associative; drawings full of lying dimensions usually trace here.
- DIMSCALE / annotation scale machinery — the old-school DIMSCALE vs. annotative styles war. Mixed-scale drawings come from mixed eras of this setting.
The "file behaves strangely in the other office" cluster
- SAVEFMT / default save version — the DWG version the file saves as by default. Mixed-version offices suffer silent upgrades; check the file's actual version (the AC code in the first six bytes) before blaming geometry.
- PROXYGRAPHICS — controls whether proxy objects store display images. Explains why third-party-object drawings look fine on one machine and hollow on another.
- XREFNOTIFY — the "drawing has unreloaded xrefs" nag behavior.
The workflow-quality four
- PICKFIRST — enables noun/verb selection (select then command). 0 forces the old command-first workflow; users complain their selection "clears."
- DRAGMODE — how objects display while dragging. Set to AUTO for live dragging.
- TOOLTIPS — yes, people turn them off and forget.
- LAYOUTREGENCTL — controls whether layouts re-render on switch; performance-relevant on huge sheet sets.
How to see and reset them all
Type SETVAR, then ?, and AutoCAD lists every variable with its current value alphabetically — the full inventory, no dialogs needed. SYSVDLG gives the same in a searchable, saveable dialog.
For teams: the variables worth standardizing (MIRRTEXT, DIMASSOC, FILEDIA, OSMODE at login) belong in your template and deployment defaults, not in tribal memory.
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