How to Batch Resize Hundreds of Photos at Once

Resizing one photo is trivial. Resizing four hundred from a holiday, a property listing or a year of site photographs is a different problem, and it is where people end up either paying for software they will use once or doing it individually for an entire evening.

Both desktop platforms can do it with tools that are already there or free from the maker. Neither is obvious, which is why the task has a reputation it does not deserve.

Before you start: copy the originals

Batch operations are fast and irreversible. A setting typed into the wrong box applies to every file before you have finished reading the dialog.

Copy the folder. Not move — copy. Work on the duplicate and keep the originals untouched until you have checked the output. This takes a minute and prevents the single worst outcome in this entire article.

The other reason to keep originals: resizing down is a one-way operation. The discarded pixels are gone, and no amount of upscaling brings back the detail.

Decide the target first

Resizing to the wrong size and doing it again is worse than taking a minute to think, because each pass costs quality on a JPG.

Work in pixels on the long edge, and let the tool scale the short edge to match. That handles portrait and landscape photos in one pass, which “resize everything to 1600 × 1200” does not — it either distorts the portrait shots or leaves them an unexpected size.

For print, the long-edge number is not a useful starting point. Start from the printed dimensions and the required resolution instead, which is the arithmetic covered in what 300 DPI actually means.

Windows: PowerToys Image Resizer

Microsoft PowerToys is a free utility set published by Microsoft. Image Resizer is one of its modules and it adds a right-click entry to File Explorer.

1. Install Microsoft PowerToys from the Microsoft Store or from Microsoft’s own download page.
2. Confirm Image Resizer is enabled in the PowerToys settings.
3. In File Explorer, select the photos. Ctrl+A selects a whole folder.
4. Right-click → Resize pictures. On Windows 11 this may sit under Show more options.
5. Choose a preset or Custom, set the dimensions, and check the Fit behaviour.
6. Click Resize.

Three settings worth understanding before you click:

Fit, Fill or Stretch. Fit scales the image so it sits within your dimensions and preserves the aspect ratio — this is the one you want. Fill crops to fill the box. Stretch distorts, and exists for reasons nobody can explain.

Only shrink larger pictures. Tick it. Without it, a photo smaller than the target gets upscaled, which adds file size and removes sharpness.

Overwrite the original files. In the advanced settings. Leave it off. With it off, you get new files with a size suffix and your inputs survive a mistake.

Hundreds of files take a couple of minutes. Progress appears in a small window and it processes several at once.

Without PowerToys

If you cannot install software, Windows has no built-in batch resize. The practical alternatives are to use our image compressor, which handles a set of files in your browser with nothing uploaded, or to script it. A for loop over ImageMagick is the standard answer if you are comfortable at a command line.

macOS: Preview, and nothing else needed

Preview handles multi-file resizing natively, which almost nobody knows.

1. Select every photo in Finder. Cmd+A for a whole folder.
2. Right-click → Open With → Preview. They open in one window.
3. In Preview, show the sidebar (View → Thumbnails) and press Cmd+A to select all the thumbnails.
4. Tools → Adjust Size.
5. Set the units to pixels, enter the long-edge value in Width or Height as appropriate, and leave Scale proportionally ticked.
6. Tick Resample image.
7. Click OK, then File → Save.

Preview applies the change to every selected image. The mixed-orientation problem applies here too: entering a width resizes landscape photos correctly and makes portrait ones taller than intended. Sort by orientation and do two passes if the folder is mixed.

Preview saves over the open files, so the copied-folder rule matters particularly here.

Automator and Quick Actions

For a resize you will do repeatedly, build it once.

Open Automator, create a Quick Action, set it to receive image files from Finder, and add the Scale Images action. Prefix it with Copy Finder Items so the originals survive. Save it with a name, and it appears in Finder’s right-click menu under Quick Actions from then on.

This gives you the PowerToys experience on macOS, built once in about five minutes.

Traps worth knowing about

Orientation flags. Phone photos are often stored in the sensor’s native orientation with a metadata flag saying “rotate this 90 degrees when displaying”. A batch tool that strips metadata without baking the rotation into the pixels leaves a third of your photos sideways. Both tools above handle this correctly; some older utilities do not, so check a portrait shot in the output.

Metadata. Resizing usually drops EXIF data, including GPS coordinates. This is often desirable — see removing EXIF data from photos — but if you rely on capture dates for organising a library, check whether your tool preserves them.

Progressive quality loss. Each JPG save re-encodes. Resizing an already resized folder compounds the damage. Always resize from the originals, which is the other reason to keep them.

File size is not dimensions. A resized photo may still be too large for a specific limit, because resizing and compressing are separate operations. Reducing an image for an upload limit covers the size side, and how to compress images covers doing both in the right order.

What to expect

Four hundred photos at 4000 pixels, resized to 1600, typically drop from several gigabytes to a few hundred megabytes and take two to five minutes to process. The saving is large because file size scales with the square of the dimensions — going from 4000 to 1600 pixels removes roughly 84% of the pixel data before compression does anything.

The honest limit is that no batch tool makes judgements. It applies one setting to every file, so a folder containing both wide landscapes and tight portraits gets treated identically. For a set where individual framing matters, batch resizing gets you most of the way and a handful of files still need attention.