Folder Comparison Deep Dive — Detect Every Difference Between Cloud Storage Locations

March 11, 2026 · 4 min read

Senior Engineer

You ran a backup last week. Did every file make it? Are the sizes correct? Is anything missing? The only way to know for sure is to compare the source and destination file by file. That's what Folder Comparison does.

Folder Comparison is one of RcloneView's most valuable features. It compares two storage locations — any combination of local, NAS, and cloud — and shows you exactly what's different. Missing files, size mismatches, date differences, and files unique to one side are all clearly identified.

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One-click jobs: Copy · Sync · Compare
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Works with Google Drive, OneDrive, Dropbox, S3, WebDAV, SFTP and more

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What Folder Comparison Shows

File categories

After comparing two locations, files are categorized:

Match — File exists in both locations with the same size and modification time. ✅
Left only — File exists only in the source (left side). May need to be copied.
Right only — File exists only in the destination (right side). May be an orphan or extra copy.
Different — File exists in both locations but differs in size or date. May need to be updated.

When to Use Folder Comparison

1) After backup — verify completeness

After any Copy or Sync job, compare source and destination:

All match? → Backup is complete.
Left only files? → These weren't backed up. Investigate why.
Right only files? → Files deleted from source but still in backup (expected with Copy jobs).

2) Before sync — preview changes

Before running a Sync job, compare to see what will change:

Left only → Will be copied to destination.
Right only → Will be DELETED from destination (Sync only!).
Different → Will be overwritten.

This is like a visual dry run.

3) After migration — confirm nothing is missing

After migrating from one cloud to another:

Compare old cloud vs new cloud.
Every file should be "match" or "right only" (already at destination).
Any "left only" files were missed and need re-transfer.

4) Regular audits — detect drift

Even with scheduled syncs, things can go wrong silently. Monthly comparisons catch:

Failed transfers that weren't reported.
Rate-limited files that were skipped.
Corrupted files (different sizes).
OAuth tokens that expired mid-job.

Practical Examples

Compare Google Drive and S3 backup

Source: Google Drive (primary). Destination: S3 (backup).

Expected results after a healthy backup:

Most files: Match ✅
Some "left only": Files added to Google Drive since last backup (will be copied next time).
Few "right only": Files deleted from Google Drive but retained in backup (this is good — your backup preserved them).

Compare two NAS volumes

Left: NAS Volume 1 (active data). Right: NAS Volume 2 (mirror).

Any difference indicates the mirror is out of sync. Fix immediately.

Compare before decommissioning a cloud account

Before canceling Dropbox:

Compare Dropbox vs Google Drive (where you migrated data to).
Ensure zero "left only" files (everything from Dropbox is on Google Drive).
Only then cancel Dropbox.

Comparison Options

Check methods

Size — Compare file sizes. Fast but doesn't catch bit-level corruption.
Modification time — Compare timestamps. Useful for detecting updated files.
Checksum — Compare file hashes (MD5, SHA1). Slowest but most thorough. Catches bit-rot and corruption.

For critical data, use checksum. For routine checks, size + modification time is sufficient.

Performance tips

Large directories (10,000+ files) — Comparison may take several minutes. Be patient.
Cross-cloud comparison — Requires listing both clouds. Use --fast-list for efficiency.
Narrow the scope — Compare specific subdirectories instead of the entire cloud for faster results.