Hands-Off File Conversion on Windows: Watch Folders or Command Line?
By Jordan Blake
The short answer
There are two ways to automate file conversion on Windows. A watch folder reacts the moment a file appears, which suits a steady trickle of incoming files on a local disk. A scheduled command-line job runs at set times, which suits batches, network shares, and servers. Most teams end up using both.
You can build either pattern yourself with PowerShell and a free tool like ImageMagick, or use a converter that has both built in. reaConverter, a Windows batch converter from ReaSoft Development that handles 800+ formats, can convert files automatically as they land in a folder and also ships a command-line tool for scheduled jobs. Both features are part of reaConverter Pro.
What are the two ways to automate file conversion?
Every hands-off conversion setup is one of two patterns, whatever tool runs it.
Event-driven: the watch folder. A program asks Windows to report changes in a folder. When a new file appears, it converts that file right away. Latency is seconds. Nothing runs when nothing arrives.
Time-driven: the scheduled job. Task Scheduler starts a command at fixed times or intervals. The command looks at a folder, converts whatever qualifies, and exits. Latency is the interval you choose, from one minute to once a night.
The difference that matters most in practice is where the files live. Windows reliably reports file changes on local disks. On network shares, change notifications are much less dependable, so a watch folder aimed at \\server\share may simply never fire. A scheduled job does not depend on notifications at all; it just looks.
How do you choose between them?
Answer four questions about the workflow, and the pattern usually picks itself.
Question | Points to a watch folder | Points to a scheduled job |
Where do source files live? | A local disk on the converting machine | A network share, NAS, or another server |
How do files arrive? | One at a time, unpredictably, all day | In batches, or at known times |
How fast must output appear? | Within seconds | Within minutes or by the next morning |
Who maintains it? | Someone who prefers a settings dialog | Someone comfortable with scripts and logs |
Two situations come up constantly. A backlog of existing files is always a scheduled or one-off command-line job, because a watch folder only reacts to new arrivals. And a share that everyone uses can still get a watch folder, as long as the converter runs on the server that owns the disk, where the folder is local.
Which tools can do it?
You can assemble automation from free parts or buy it built in. The free route costs time; the paid route costs a license.
Tool | Cost | Watch folder | Scheduled job | Notes |
PowerShell FileSystemWatcher | Free, built into Windows | DIY script | Yes, with Task Scheduler | You write the error handling; bursts of files can overflow its event buffer |
ImageMagick | Free, open source | Through your own script | Yes | Huge format range for images; PDF needs Ghostscript; no CAD or GIS formats |
IrfanView | Free for non-commercial use | No | Yes, via /convert | Simple syntax; businesses need a license |
NConvert (XnSoft) | Free for non-commercial use | No | Yes | Command-line companion to XnView |
reaConverter Pro | Paid, free trial | Built in, runs as a Windows service | Yes, via cons_rcp.exe | Both patterns share one settings file; local folders only for watching |
The hidden cost of the DIY route is not the first script. It is the second year, when someone has to find out why the script silently stopped converting a third of the files.
Setting up both patterns in reaConverter
reaConverter keeps conversion settings in two portable files: a .cfg for format, destination, and naming, and an .act for edits such as resizing or watermarks. Build the job once in the interface, save both files, and the watch folder and the command line will produce identical output.
A watch folder in five steps
Open Menu → Watch folders, switch it ON, and click Add new folder.
Pick the folder to monitor. Tick Read subfolders if files arrive in a tree.
Untick Process all files without filtering to add masks. Wildcards like *.tif work, and so do regular expressions for strict naming rules.
Choose Subfolder of source folder for output. It keeps results apart from originals and avoids conversion loops.
Set the format under Save files as, load your .act file, tick Create log file, and click Create Watch folder.
The watch folder runs as a Windows service, so it keeps working with the program closed and nobody logged in.
A scheduled job for a network share
This command turns scanned TIFFs on a file server into searchable PDFs, moves finished originals out of the queue, and quarantines anything that fails:
"C:\Program Files\reaConverter\cons_rcp.exe" -source_folder "\\fileserver\scans\incoming\" -source_ext tif -dest_path "\\fileserver\scans\pdf\" -dest_ext pdf -create_searchable_pdf 1 -move_files 1 -move_files_folder "\\fileserver\scans\done\" -move_unprocessed_files 1 -move_unprocessed_files_folder "\\fileserver\scans\failed\" /hide
In Task Scheduler, choose Run whether user is logged on or not, run it under a service account with rights on all four folders, and use UNC paths rather than mapped drive letters, which do not exist outside an interactive session.
Reliability checklist for unattended conversion
The conversion step rarely breaks. The plumbing around it does. Run through this list before any job goes live, whichever tool you use.
☐ Half-copied files. Large files appear in a folder before the copy finishes. Have senders copy into a staging folder and then move files into the queue, since a move on the same volume is instant.
☐ Output loops. Never write output into the folder being watched with the same file type as the input. Use a separate output folder or subfolder.
☐ Quarantine. Move files that fail into their own folder. An empty quarantine folder is the fastest health check there is.
☐ Exit codes. Check them in your script. With reaConverter, 0 means success, 7 means there was nothing to convert, and 8 means some files failed.
☐ Overlapping runs. In Task Scheduler, set Do not start a new instance so a slow run cannot collide with the next one.
☐ Permissions. Test the exact command under the service account before scheduling it. Most first-night failures are access errors, not conversion errors.
☐ Logs that rotate. Write a log per day or per run. One endless log file is as useless as no log.
☐ A week of rehearsal. Point the job at a copy of real data for a week before it touches production folders.
Honest limitations
reaConverter Watch Folders monitor local folders only. Pointing one at a share or a mapped drive does nothing. Either install reaConverter on the file server, where the folder is local, or poll the share with a scheduled command-line job.
Automation is a Pro feature. The free Lite edition converts in batch from the interface and the right-click menu, but it has no watch folders or command line.
Windows only. There is no macOS or Linux version. Cross-platform shops may prefer ImageMagick or a similar open-source tool in a container.
Polling has a floor. Task Scheduler repeats a task at most once a minute. If you truly need faster reaction on a share, a small loop script that sleeps and calls the converter is the workaround.
DIY scripts age badly. PowerShell and ImageMagick are free and flexible, but every edge case is yours to handle and document.
FAQ
How do I automatically convert files dropped into a folder on Windows? Use a watch folder. Either script one with PowerShell's FileSystemWatcher and a command-line converter, or use a converter with watch folders built in, such as reaConverter Pro. Keep the watched folder on a local disk.
Can a watch folder monitor a network share? Not reliably. Windows change notifications are dependable on local disks only. Run the converter on the server that owns the share, or schedule a command-line job that checks the share every few minutes.
How do I run a conversion job on a server with nobody logged in? Schedule the command in Task Scheduler with "Run whether user is logged on or not", run it as a service account, use UNC paths, and hide the console window. In reaConverter that last part is the /hide switch.
How do I avoid converting the same files twice? Move each file out of the input folder after it converts, so the folder only ever holds unprocessed work. In reaConverter, -move_files does this, and -overwrite 0 skips files whose output already exists.
What should happen to files that fail to convert? Move them to a quarantine folder and alert someone when it is not empty. Leaving them in place means the job retries them on every run.
About the author
Jordan Blake writes about batch conversion and automation for the reaConverter team and maintains the guides at howto.reaconverter.com. Jordan's articles are aimed at IT generalists who keep file workflows running in offices without a dedicated automation engineer.
