MerlinCopy

A file copy you can trust with data that matters

Pick what to copy (files, folders or a mix) and where to. MerlinCopy looks at both ends, whether SSD, hard disk, USB drive or network share, and picks how to copy: how many files at once, how big a buffer, and whether to go through the Windows file cache. Then it copies, checks every copy against the source, and tells you how long it will really take, with the estimate getting sharper as the job runs.

Reliability comes before speed. Every file is written under a temporary name and gets its real name only when it is complete and verified, so a crash, a reboot, a full disk or a dropped network share never leaves a half-written file looking like a good one. The job stops where it was and resumes from there, mid-file for big files.

Is it for you?

It's a good fit if you move large folders to a NAS, a file server or a USB drive, migrate data between servers, or run nightly copies, and want to know that what arrived is what left. It suits admins who want a command line with exit codes for scripts as much as people who just want a progress bar they can believe.

It's probably not for you if you need a backup product with versions and retention, or two-way sync between PCs. MerlinCopy copies, moves and mirrors one way.

Features

Copying

• Copy, Sync newer, Move and Mirror. Move deletes each source file only after its copy is verified and only if the source didn't change in the meantime.
• Mirror shows you every removal first. Nothing is removed until you have seen the full list and confirmed it, and removed items are set aside in a hidden folder at the destination rather than deleted, unless you choose otherwise.
• Rules for files already at the destination: ask, overwrite, keep the newer, copy only if different, skip or rename. Nothing is overwritten without a rule you chose.
• Keeps timestamps, attributes and alternate data streams; optionally permissions. Handles long paths, sparse and compressed files, and junctions and symbolic links.
• Filters by name, folder, size and date. Presets and .mcjob files save a whole job to run again, or on a schedule.

Checking

• Verification by default: each copy is read back from disk and compared with the source before it gets its real name. A copy that doesn't match is made again. Paranoid mode compares SHA-256 of both sides.
• Pre-flight checks before anything is written: free space, file system limits, locked files, copying a folder into itself.
• Compare and dry run list what differs, and what a copy would do with each file, without copying anything.
• Every job keeps a log, and History exports a CSV of every file or an HTML report of what wasn't copied and why.

Time estimate and control

• The time left as a range with a finish time, priced from what is left (thousands of small files cost more than one big one) and learned from the copy as it runs. It remembers how fast two places were for next time.
• Pause, resume, cancel and resume later. Change the number of workers or set a speed limit while it runs, or schedule a limit for working hours.
• Jobs on different drives run at the same time; jobs on the same drive take turns.
• When done: open the folder, run a command, sleep or shut down, with a countdown you can cancel.

Command line and Explorer

• A MerlinCopy command for scripts and scheduled tasks, with documented exit codes: copy, resume, compare, analyze and run a preset.
• "Copy with MerlinCopy" and "Paste with MerlinCopy" on Explorer's right-click menu (installed version).
• Installed or portable: the portable version runs from a folder or USB stick and writes nothing outside its own Data folder.

Price

Free. No trial, subscription, account or ads.

Privacy

MerlinCopy works entirely on your PC. It doesn't phone home, check for updates, collect usage data or send anything anywhere. Its job history and speed measurements stay on your PC.

Requirements

Install

1. Download the zip, extract it, and run the setup file inside. Setup and the app are digitally signed by Virtual Merlin, Inc., so Windows shows that name as the publisher. If Windows still shows "Windows protected your PC" while the new signature builds reputation, click More info, check the publisher is Virtual Merlin, Inc., then click Run anyway.
2. Choose the extras: a desktop shortcut (off by default), the Explorer right-click entries, opening .mcjob files, and the MerlinCopy command on your PATH.
3. Drop files or folders on Sources, pick a destination, and click Analyze & Copy. Check the plan and the estimate, then click Start.

SHA-256 of the setup file inside the zip:

9C3F65A6121E07CDC7AAAC7BACF752FB759E8D730CDFB3A5506689930CBDB20A

Known limitations

• Tens of thousands of tiny files copy more slowly than with a plain copy, because each one is written under a temporary name, flushed to disk and verified. You can turn the flush or the verification off for speed.
• On Windows 11 the Explorer entries are under Show more options.
• The estimate learns as it goes and can't foresee a drive slowing down part-way through, such as an SSD whose fast cache fills up.
• A scheduled run shows a console window while it copies, and runs only while you are signed in.