Schedule Comparison Software for P6: What to Look for When Evaluating Your Options

If you are evaluating tools for comparing Primavera P6 schedules, you already know the basic requirement: load two XER files, see what changed. What separates the options is what they do beyond that — the depth of the comparison, the quality of the output, and how well the results hold up when they matter most.

This guide covers what to look for when evaluating schedule comparison software for a P6 environment.

1. File Format Compatibility

The starting point is whether the tool reliably handles the P6 file formats you actually use.

Primavera P6 exports schedules in two formats: XER (the native binary-text format) and XML (a structured export format). These two formats represent the same schedule data differently — date formats, relationship type codes, float values, and physical percent complete are all stored differently between XER and XML exports.

A comparison tool that does not properly normalize these differences will produce false positives — apparent changes that are actually just format artifacts, not real schedule changes.

Change Inspector normalizes all field values before comparison — stripping time components from dates, converting XML fraction-based percent complete to match XER's percentage format, resolving calendar and resource IDs to names rather than comparing raw IDs — to ensure the comparison reflects genuine schedule changes only.

2. Activity Comparison Depth

A complete activity comparison should cover more than just dates. Look for a tool that compares all of the following for each activity:

• Actual and early/late start and finish dates
• Planned and remaining duration
• Total float and free float
• Activity status and physical percent complete
• Constraint type and constraint date
• WBS assignment
• Primary resource
• Calendar assignment
• Driving path flag

Change Inspector compares 27 fields per activity pair, with suppression rules that eliminate false positives for fields that are irrelevant once an activity has started or finished — for example, early and late start dates are suppressed once an activity has an actual start recorded, because the CPM-calculated dates are no longer meaningful at that point.

3. Relationship Comparison

Logic change detection is where many basic comparison tools fall short. The relationships tab of any comparison tool should show:

• Relationships added between the two schedules
• Relationships removed
• Lag changes on existing relationships
• The predecessor ID, successor ID, and relationship type (FS, SS, FF, SF) for each changed link

This matters because logic changes are often the most consequential changes in a schedule update — they can shift the critical path without any date on any individual activity changing obviously.

One important technical detail: if a relationship type changes in P6 — for example, a Finish-to-Start relationship is replaced with a Start-to-Start — this should appear as a removal of the original relationship and an addition of the new one, not as a modification. This is how Change Inspector handles it, which accurately reflects what happened in the schedule.

4. Schedule Options Comparison

This is easy to overlook but important: two XER files can produce different float values and dates not because the schedule logic changed, but because the P6 calculation settings changed. Retained Logic vs. Progress Override, float type, critical float threshold — any of these affect CPM results.

A comparison tool that flags the P6 schedule options alongside activity changes gives you the context to explain apparent discrepancies that would otherwise look like schedule manipulation.

5. Export Quality

The comparison output needs to be useful to people beyond the scheduler. Consider:

• Owner reporting: Can the results be exported to a formatted, color-coded Excel report that a non-scheduler can read?
• Subcontractor review: Can you filter the results to show only changes relevant to a specific WBS or scope of work?
• Claims documentation: Is the output organized in a way that would hold up in a formal dispute or Time Impact Analysis?

A report that requires significant manual reformatting before it can be shared is a hidden time cost. Look for a tool whose export is ready to use directly.

6. Version History Across Multiple Updates

A single comparison between two files tells you what changed between those two dates. A project with 24 monthly updates needs something more systematic — a running record of every version, with the ability to compare any two files in the log.

Change Inspector's Schedule Log lets you catalog all schedule files for a project in chronological order, and run comparisons across any two entries in the log. The export includes the full schedule log as a CSV or Excel file for external record-keeping.

7. DCMA Health Check Integration

If your projects require DCMA compliance — or if you want to use the 14-point assessment as a general schedule quality standard — look for a tool that runs the health check alongside the comparison, not as a separate workflow.

Change Inspector's Health Check module runs the full DCMA 14-point assessment on any loaded schedule file, with adjustable thresholds to match your contract requirements. The Excel export produces a formatted scorecard with violation detail sheets for every failing check.

A Practical Evaluation Approach

When comparing schedule comparison tools, the most useful test is to run them against your own files:

1. Load two consecutive updates from a real project
2. Look at the activity count: how many changes does the tool report, and do they make sense?
3. Check the relationships tab: are logic changes surfaced clearly with full predecessor/successor detail?
4. Export to Excel: is the output ready to attach to a report without reformatting?
5. Run the DCMA health check if available: does the scorecard match your expectations for the schedule's quality?

Change Inspector offers a 30-day free trial with no credit card required. You can run all of these tests on your own P6 files and assess the results directly.