Diff thousands of files between two product versions

Step 1: Organize both file setsSharePointOneDrive

Create two clearly named folders (e.g., "v1-release" and "v2-release") with matching internal structure, so a file in one has an obvious counterpart in the other.

Cowork needs that unambiguous before/after pairing to compare against, and a mismatched folder structure is the easiest way to get a diff report full of false "new file" or "removed file" flags.

Step 2: Set Cowork loose on the comparisonCopilot Cowork

This is the kind of large-scale, long-running comparison Cowork is built for — thousands of files compared end-to-end without a human doing the diffing by hand.

Prompt idea:

Compare every file in the "v2-release" folder against its counterpart in "v1-release." Group the changes into: content changes, new files, removed files, and formatting-only changes. Flag anything that looks like an unintentional regression.

Step 3: Review the grouped summary, not every fileCopilot Cowork

The value here is the grouping — spend your review time on the "content changes" and "possible regressions" buckets, not skimming every file yourself.

Step 4: Spot-check a sample from each groupSharePointOneDrive

Pull a handful of files from each category and confirm the classification is accurate before trusting the full report.

Check the work

• Spot-check files from each change category to confirm they're classified correctly.
• Confirm the file counts add up to the actual size of both folders — nothing silently skipped.
• Treat "possible regression" flags as a starting point for investigation, not a final verdict.

Source: Microsoft, "Copilot Cowork is now generally available" (June 2026)