Watch a folder and auto-compress every screenshot

Set up a watch-folder automation once and never compress a screenshot by hand again. 1FileTool's Folder Monitor watches a folder while the app is open, and every new file that lands there gets run through a tool you pick — here, Compress Image.

What you'll need

• 1FileTool 1.10.0 or later on macOS (Apple Silicon or Intel), Windows, or Linux.
• A folder to watch — for this tutorial, the folder your screenshots land in.

The ZIP has three synthetic PNG screenshots (Screenshot 2026-09-26 at ….png, 2–3 MB each, the size real Retina-class captures reach). Drop them in your watched folder one at a time to see the automation fire.

The monitor writes compressed_<name>_<timestamp>.png to your output folder and leaves the original untouched — no rename, no overwrite. And the basics are all free: plain "run this tool on new files" monitors need no Pro. (Conditions, rename-and-sort Smart rules are the Pro tier.)

Steps

1. Open Folder Monitor

Launch 1FileTool and click Folder Monitor in the sidebar's Automation group. The page shows your monitor stats — unread events, active monitors, last activity — and a Create Monitor card.

2. Pick the folder

Under Folder, click the picker button and choose the folder to watch — for this tutorial, the one where your screenshots land (or a scratch folder holding the sample PNGs).

3. Keep the type on Tool

Leave Type on Tool — a monitor can also run a saved Recipe or an Organize action, but a single tool is all this job needs.

4. Choose Compress Image

In the Tool dropdown, pick Compress Image — "Compress new images with the default quality settings." Its accepted extensions include .jpg .jpeg .png .webp .gif .tif .tiff .heic .heif, so PNG screenshots qualify.

The same dropdown has 30+ other options — compress PDFs, convert HEIC, mute videos — for whatever folder job you have in mind.

5. Create the monitor

Click Create. The monitor appears in the list as Watching, with a file counter and last-run time.

6. Drop a screenshot in

Copy Screenshot 2026-09-26 at 09.14.22.png into the watched folder. Within a few seconds the monitor fires and the compressed copy appears in your output folder.

The result

After the drop:

• ~/Documents/1FileTool/compressed_Screenshot …_1790395910439.png — a compressed copy lands in the output folder.
• The monitor row shows Processed 1 file(s) with the last-run time, and the event appears under Recent Activity ("Saved compressed_…png").
• The original screenshot stays exactly where you put it.

Monitors run while 1FileTool is open — close the app and watching pauses. And each file the monitor processes counts individually toward the free plan's 8 files per day.

If it didn't work

• Nothing fired. Folder Monitor only picks up files that arrive after the monitor is created — files already in the folder are skipped. Drop a fresh copy in. The app also needs to be open; monitors don't run in the background.
• "Paused" at the daily limit. When the free tier's 8 processed files are exhausted for the day, the monitor pauses itself and resumes tomorrow — or Pro removes the cap.
• Wrong file types. The monitor only runs on the extensions its tool accepts — Compress Image won't fire on a .pdf or .mov.
• Two compressed copies. Two monitors can watch the same folder — check the monitor list and delete the duplicate.

Try next

Want to see the compression itself? Try it on an image in the browser:

Related

• Folder Monitor reference
• Free vs Pro
• Output folder and Replace source
• Compress Images tool page