# Error Checker

Opens via Tools › Error Checker. Also runs automatically before saving when issues are present.

Scans the entire mission for structural problems, design errors, configuration warnings, and potential issues. Results are listed by severity with a description of each problem found.

## Controls

Control | Description
--- | ---
Rerun | Runs the check again. Use this after making fixes to confirm they are resolved.
Check Potential Issues | When checked, Potential Issue entries are included in the results alongside errors and warnings. When unchecked, potential issues are silently omitted.
Apply Auto-Corrections | When checked, FRED automatically corrects issues it can resolve without user input each time a check runs. Only applies to correctable errors and warnings; Critical Errors are never auto-corrected. Auto-corrections are applied before results are displayed.
Status bar | Shows a summary of the most recent check: the total number of entries found, or No check has been run yet before the first run.

## Severity levels

Severity | Meaning
--- | ---
Critical Error | A serious structural problem that FRED cannot automatically correct. The mission may fail to load or behave unpredictably in-game. Must be fixed manually before the mission is usable.
Error | A mission design problem that must be fixed. The mission may not play correctly.
Warning | A problem that can be (or has been) auto-corrected. Review the change before saving.
Potential Issue | A situation that may be intentional but is worth reviewing. Only shown when Check Potential Issues is checked.

## What is checked

The checker inspects the following areas of the mission:

- Object list integrity and name uniqueness
- Ships — SEXPs, AI goals, anchor references, docking configuration, and loadout weapon availability
- Wings — structure, SEXPs, AI goals, anchor references, wave thresholds, and accepted orders consistency
- Player starts and player wing membership
- Waypoint path names for conflicts with object names
- Reinforcement name references
- Mission events and mission objectives — SEXP validation
- Briefings — icon ID uniqueness
- Debriefings — SEXP validation
- Asteroid field target ship name validity
- Initially-docked groups — must have exactly one non-false arrival cue
- Team loadout — weapons used in starting wings must be present in the team loadout pool

## Pre-save mode

When saving a mission that has unresolved errors, the Error Checker opens automatically in pre-save mode. In this mode three additional buttons appear at the bottom of the dialog:

Button | Description
--- | ---
Cancel | Aborts the save and returns to the editor so issues can be addressed.
Save As Is | Saves the mission despite the reported issues.
Fix and Save | Applies all available auto-corrections and then saves. Only available when Apply Auto-Corrections is checked.

## Preferences

The Check Potential Issues and Apply Auto-Corrections settings are also found in File › Preferences › Error Checker. They share the same stored value — changing one updates the other. Use Preferences to set the default behavior for all future check runs.