jCopy and Fix - documents that open on Windows.

Two things go wrong, every time

Neither is your fault, and neither is fixed by copying more carefully. They are both side effects of how macOS writes to a stick formatted for Windows.

The hidden files

macOS attaches invisible housekeeping information to every file it creates. A USB stick formatted for Windows has nowhere to store it, so the Mac writes it into a companion file named ._ plus the original name. macOS hides files that start with a dot. Windows does not.

The result is a second, broken copy of every document sitting next to the real one. Open the wrong one and Word, Excel or Acrobat reports a damaged file. jCopy and Fix removes each companion file straight after the document is copied, so the stick arrives clean.

The dates

An ordinary copy stamps today's date on everything it writes. On Windows, "Date created" is a column people sort by - so twenty years of documents collapse onto a single day, and finding the current version of anything becomes guesswork.

jCopy and Fix reads the date from inside each document and writes it to the copy:

• Word, Excel and PowerPoint - from the document properties Office stores inside the file
• PDF - from the document information the PDF carries
• Everything else - from the file's own modification date

Each file gets its last-modified date, or its created date if it was never modified. Both the "Date created" and "Date modified" columns on Windows are set, because either one may be what you sort by.

Two modes

The details that bite

• Names Windows refuses - characters like : ? * " < > |, names ending in a dot or a space, and reserved words like CON and LPT1 are renamed, and every change is listed in the report
• Case-only duplicates - a USB stick treats Report.pdf and report.pdf as the same file, so an ordinary copy silently loses one. jCopy and Fix keeps both
• Mac clutter left behind - .DS_Store files, existing ._ files, and Word's ~$ lock files never reach the stick
• Wrong-format sticks caught early - if the stick is formatted for Macs only, Windows cannot read it at all. jCopy and Fix says so before you copy anything, rather than after
• Re-copying is safe - running it again over the same folder refreshes the stick instead of piling up duplicates

Careful by default

A hidden file is only deleted when its contents confirm what it is - a file of your own that merely happens to be named ._notes.txt is left alone and reported as skipped. Trash and system folders are never touched. After each date is written it is read back off the disk, and any that did not take is reported rather than assumed.

Who it's for

System requirements

• macOS 26 or later
• Apple Silicon or Intel processor
• A USB stick formatted as exFAT (or FAT32) - the formats Windows can read

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