Two-folder merge preview
Compare incoming and destination folders for exact matches, one-sided files and same-path conflicts.
FREE · OPEN SOURCE · LOCAL-FIRST
Understand two folders.Merge without the guesswork.
Find renamed duplicates. Prevent merge mistakes.
DUPESPACE is a free, open-source folder merge preview and duplicate file tool. Find exact content under different names, files missing from either side, and same-path version conflicts. Files are read on-device and never sent to a DUPESPACE server.
0/100
Merge readiness · ExampleRelationships still unknownCompare before copying
LOCAL CONTENT ANALYSISMatching file contents
82%DESTINATION · EXISTINGINCOMING · EXACT MATCH
Beach.jpgPhotos / Travel / Beach.jpgExists
IMG_3482.jpgIncoming / IMG_3482.jpgCompare
Report.pdfDocuments / Report.pdfExists
Client-brief.pdfIncoming / Client-brief.pdfCompare
Demo · Copy avoided0.0 GB
Matching full content2Folders compared side by side
5Clear merge categories
0Files sent to a server
0Web write permission
MERGE WITH CONTEXT
A merge map for problems filenames cannot explain.
A different name can hide identical content. The same relative path can hide a different version. DUPESPACE separates both before you copy or overwrite anything.
Renamed duplicate detection
Complete content fingerprints find identical files even when the names and folder locations changed.
Purpose-aware review
Project, application and backup contexts are flagged because identical bytes can still serve different roles.
HOW IT WORKS
Compare actual content, not just names.
Choose an incoming folder and a destination. DUPESPACE narrows candidates by size and sample, then verifies complete content locally. The result separates exact matches, renamed or moved matches, new files and version conflicts.
Open merge preview- 01ChooseSelect incoming and destination folders
- 02VerifyMatch full content on this device
- 03ReviewSee the merge map and export CSV
LOCAL-FIRST PRIVACY
Your files stay on your device.
No account is required. Choosing a folder grants this tab on-device read access; files are not sent to a DUPESPACE server, and the page cannot copy, overwrite or delete them.
No server transfer. No write permission.
Only files explicitly handed to the browser file picker are available to the page. Close the tab to clear unexported in-memory results.
WHY TRUST DUPESPACE
Read the code. Verify the claims.
Clear boundaries
Web analysis is read-only. Windows protects projects, selected subfolders and at least one keeper per group.
Purpose before matching
Identical content does not prove a copy is disposable. Context and protection rules come before removal.
Free and open source
Inspect the implementation, report issues or run your own copy under the MIT License.
View source on GitHubFrequently asked questions
What does DUPESPACE do?
DUPESPACE is a free, open-source folder merge preview and duplicate file tool. The web app compares incoming and destination folders for renamed exact matches, one-sided files and version conflicts. The Windows app provides recoverable duplicate cleanup.
Can it find a file after it has been renamed or moved?
Yes. Folder merge preview verifies complete content rather than relying on a filename or relative path. Exact content at a different name or location is marked as already present; different content at the same path is marked as a version conflict.
Are similar-looking photos duplicates?
Not necessarily. DUPESPACE compares complete file content, not visual similarity. Cropping, compression, conversion or metadata changes can produce different files. Similar-photo search is not currently included.
What about identical files in separate software projects?
The browser never deletes files and flags common project contexts. Windows excludes detected projects and package folders. Rules cannot identify every custom workflow: protect important working subfolders and review each copy’s purpose.
Does browser analysis upload my files?
No. Filenames, paths, contents and comparison results are processed inside your browser, not uploaded to DUPESPACE. The web app has no permission to move or delete local files.
Does the Recycle Bin immediately free disk space?
Not necessarily. Trashed files may still occupy the original disk until its Recycle Bin is emptied. Review them first. NAS, network drives and some external devices may have different Recycle Bin support; a failure never triggers permanent deletion.
FILE INTELLIGENCE
Not another duplicate list. A merge map you can act on.
Byte equality does not prove two files serve the same purpose. DUPESPACE narrows candidates, verifies complete content, then separates version conflicts, context risks and renamed exact matches.
MERGE READINESS
24/100From unknown relationships to a reviewable map
Before comparisonMerge map ready
Renamed matches exposedVisual example not device data
CONTENT PIPELINE
Fast filtering, complete verification
The interface stays simple while multiple verification layers run locally. Bars illustrate the narrowing pipeline, not your data.
DECISION PRIORITY
Actual logicThe risky items surface first
DUPESPACE separates byte equality from purpose. The report prioritizes what needs a human decision.
Version conflictsSame path, different content: resolve first
Context reviewKeep project, app and backup copies by default
Renamed exact matchesAvoid copying again without deleting anything
FILE GUIDES
A little context makes cleanup safer.
Practical guide
How to find duplicate photos: exact matches vs similar images
Learn why identical-looking photos may be different files. Compare exact duplicates locally without uploading, review paths and organize copies without risking your backup.
Practical guideHow to clean duplicate files on Windows without breaking projects
Duplicate does not mean unnecessary. Learn a safe Windows cleanup workflow: choose folders, protect projects and backups, review copies and check the audit report.
Practical guideHow to merge two folders without duplicate files or silent overwrites
Compare two folders before copying. Find renamed exact matches, one-sided files and same-path version conflicts locally in your browser without uploading or changing files.
Practical guideWhich duplicate file should you keep? Do not rely on names or dates alone
When content matches exactly, start with protection rules, folder purpose, backup state and trustworthy timestamps. Creation time is evidence, not proof of an original.