How to Bulk Resize Many Images at Once

To bulk resize images, open Resize Image, add up to 50 files in one go, type one width, and click Resize. Every image comes out at that width with its own height, and the set downloads as a single zip. The resizing runs in your browser, so the images are never uploaded.

How to bulk resize images, step by step

1. Add the images. Open Resize Image and drop the files on it, or click to pick them. It takes JPG, PNG, WebP and other common image types, up to 50 files per batch and 50MB per file.
2. Type the width in pixels. The box starts at 1920. Leave "Lock aspect ratio" ticked and the height fills itself in.
3. Read the "New size" line. It shows the output size next to the original. It describes the first image in the batch only.
4. Click Resize, then download. The button reads "Download 4 files (.zip)", or however many you added, and saves babapic-resized.zip.

What happens to images of different shapes?

Each image gets the width you typed and keeps its own proportions. A landscape photo and a portrait photo leave the batch equally wide and unequally tall, and neither is stretched. This is what three of the four files in our test batch did at a width of 800:

One thing on the result screen can mislead you. It reports a single size for the whole batch, taken from the first image. Ours said "Resized 4 files to 800 × 600px" while the portrait file inside the zip was 800 x 1200. The files are right; the summary line only knows about one of them. If aspect ratio is a new term, that guide explains why the heights differ.

How to give every image the same height

To match heights across a batch, type the height, then delete the number in the width box. The second half matters. With the lock on, typing a height fills in a width worked out from the first image, and the batch then follows that width. Empty the width box and the height becomes the rule for every file.

In our run, a height of 500 with the width cleared gave 667 x 500, 333 x 500 and 500 x 500 from a landscape, a portrait and a square. With the width left in, the same three came out 667 pixels wide and 500, 1001 and 667 tall.

Can you force one exact width and height?

Yes. Untick "Lock aspect ratio" and type both numbers, and every file comes out at exactly that size. Anything with a different shape is stretched to fit, so a portrait squeezed into 800 x 800 looks squashed. That setting suits a batch that already shares one shape, such as a set of screenshots or photos from one camera held one way.

For a mixed batch that has to end up one shape, crop before you resize. How to crop a photo covers that step.

What if some images are smaller than the target?

A fixed width enlarges anything narrower than it. In the batch above, the 400 x 300 image was doubled to 800 x 600, and enlarging adds no detail, only softness. Check the batch for small files before you pick a number, or let each image scale against its own size.

Resize by Percentage does the second. It has one box, marked from 1 to 500 and starting at 50. At 50% our 2000 x 1500 photo became 1000 x 750, the 1000 x 1500 portrait became 500 x 750, and the 400 x 300 image became 200 x 150. Nothing is enlarged unless you type a number above 100. Resize an image without losing quality goes through the other ways a resize costs detail.

What is in the zip?

The zip holds the resized files under the names you started with, with one exception: HEIC and HEIF photos come back with a .png ending. Three details are easy to miss:

• Every file is saved as PNG data, whatever it was before. beach.jpg comes back as beach.jpg with a PNG inside. Browsers and most viewers open it normally, and a transparent PNG stays transparent.
• The batch can weigh more than the originals. PNG is lossless and heavy for photographs. Our four test files totalled 315KB going in and 1.22MB coming out, with one of them enlarged.
• Names must be unique. Two files that share a name take the same slot in the zip, so only one survives. Rename duplicates before you add them.

To get small JPGs back, unzip the folder and drop the files into Compress Image. It also takes a batch and returns a zip, and it re-encodes a file named .jpg as a real JPEG at the same pixel size. In a separate test, three PNG files named .jpg, each 800 pixels wide, went from 1.29MB to 219KB at its default quality.

More than 50 images?

Run them in groups of 50 or fewer. If you select more, the tool keeps the first 50 and drops the rest, and the page does not tell you which were left out. The panel just reads "50 images". Sorting a big folder into numbered subfolders first makes it easy to see what has been done.

On a Mac, Preview can also resize a selection of images together. The steps are in how to resize an image on a Mac. Not sure which width to type? How to resize an image lists sensible sizes for the web, email and upload forms.

FAQ

How many images can I resize at once?
Up to 50 per batch, each up to 50MB. There is no cap on how many batches you run.

Do bulk-resized images keep their file names?
Yes, apart from HEIC and HEIF photos, whose names end in .png afterwards. The contents are PNG data even when the name ends in .jpg.

Are my photos uploaded when I resize in bulk?
No. Each image is redrawn at the new size on your own device, and the zip is assembled in the browser too.

What happens if one file in the batch fails?
The rest still finish. The result screen adds a note saying how many files couldn't be processed and were skipped.

Can I bulk resize to a percentage instead of pixels?
Yes. Resize by Percentage takes the same 50-file batch and scales each image by the same share of its own size. Resize an image by percentage explains when that beats exact pixels.