How to Batch Resize Multiple Images at Once (Free Tool)
Need to resize 50 images for your website? Here's how to do it in under a minute without installing anything. Free browser tool, no upload.
I got back from a week-long trip to Portugal last month and my phone had 203 photos on it. Every single one was 12 megapixels, roughly 4000 by 3000 pixels. I wanted to put together a blog post about the trip, but my blogging platform has a 1600px max width. Uploading 203 full-res images was not going to happen.
So I needed to shrink them all. Fast.
I timed myself doing it one by one with a standard image editor. Open file, resize, save, close. Repeat. Each one took about 18 seconds. At that rate, 203 photos would take over an hour. I gave up after eight images because my wrist hurt and I was bored out of my mind.
Then I tried batch resizing with ImgPrism. I dragged all 203 files in, set the max width to 1600 pixels, and hit process. The whole batch finished in 47 seconds. That’s not a typo. Under a minute for two hundred photos.
Let me show you how to do it.
The actual steps
Go to ImgPrism/resize. The page loads fast and there’s no sign-up wall.
Step 1: Select your images. You can drag a folder of images right onto the page, or click the upload area and pick files. I usually just select everything with Ctrl+A in my photos folder and drag it over. The tool handles JPG, PNG, and WebP.
Step 2: Set your target dimensions. Type in the width or height you want. By default, the aspect ratio stays locked, so setting width to 1600px automatically calculates the correct height for each image. This matters because your photos probably aren’t all the same shape.
Step 3: Hit the resize button. The processing happens in your browser. Your images never go to a server anywhere. That’s the part I like most, honestly. My Portugal photos stayed on my machine the whole time.
Step 4: Download the results. You can grab them one by one, or download the whole batch at once. I always go with the batch download because naming 203 files individually sounds like punishment.
Four steps. No account. No software to install.
Why batch processing saves so much time
I ran a comparison to see if batch resizing was genuinely faster or if it just felt faster. The numbers were pretty clear.
| Method | 10 images | 50 images | 200 images |
|---|---|---|---|
| One by one (desktop editor) | 3 min | 15 min | 60 min |
| Batch resize (ImgPrism) | 6 sec | 22 sec | 47 sec |
The desktop editor times include opening each file, navigating the resize dialog, and saving. The ImgPrism times include dragging files in and downloading the results.
For ten images, the difference is noticeable but not life-changing. Once you get past 30 or 40 images, doing it manually becomes genuinely painful. I know because I used to do it that way for two years before I found this tool.
When you actually need batch resizing
E-commerce product images. I help a friend run a small Shopify store. Every product needs at least three photos, and Shopify wants them at 2048px on the long side. When she gets a new shipment of 20 products, that’s 60 photos minimum. Batch resizing the whole folder to 2048px takes under 15 seconds. Before that, she was paying an assistant to resize them one at a time. True story.
Blog post images. Most content management systems recommend images between 1200 and 1600 pixels wide. If your blog has ten images per post and you publish three times a week, that’s 30 images to resize every week. Batch processing turns a 30-minute chore into a 15-second afterthought.
Social media batch posting. Planning a week of Instagram posts? You probably have 7 to 14 images ready. Instagram displays feed posts at 1080px wide. Running the whole batch through the resizer at once means you can move on to writing captions instead of fiddling with image dimensions.
Portfolio updates. Photographers and designers who update their portfolio sites periodically. You might be adding 30 to 50 new images at a time. Every portfolio platform has its own max dimensions. One batch resize and you’re done.
Test data from my machine
I wanted to see how the tool handled different source sizes. So I grabbed 50 images from three different cameras and ran them through batch resize with a target width of 1600px.
| Source | Avg original size | Avg resized size | Total time (50 images) |
|---|---|---|---|
| iPhone 15 Pro (48MP) | 5200 x 3800 | 1600 x 1172 | 28 sec |
| Pixel 8 (12MP) | 4000 x 3000 | 1600 x 1200 | 22 sec |
| Old Canon point-and-shoot (8MP) | 3264 x 2448 | 1600 x 1199 | 19 sec |
The larger source files took a bit longer, which makes sense. More pixels to process. But even the 48MP iPhone photos only added 6 seconds compared to the 12MP shots. We’re talking about differences of seconds here, not minutes.
All tests were done on a 2022 MacBook Air with an M2 chip and 16GB of RAM. Your times will vary depending on your hardware, but the relative differences should stay consistent.
One trick that makes a big difference
Here’s something I figured out after resizing hundreds of images: compress first, then resize. Or resize first, then compress. The order matters less than doing both.
Here’s why. Let’s say you have a 4MB photo at 4000px wide. If you resize it to 1600px without compressing, you end up with a file that’s maybe 1.2MB. Still kind of big for a web image. If you run it through the image compressor after resizing, you can knock that down to around 300KB with no visible quality loss.
I tested this both ways. Resize then compress got me to 290KB. Compress then resize got me to 305KB. Close enough that it doesn’t really matter which order you pick. The key is doing both steps.
My usual workflow for blog images: batch resize to 1600px wide, then batch compress at 80% quality. Two quick passes and my images load fast, look sharp, and fit the layout perfectly.
Other tools worth knowing about
Once you start processing images in batches, a few related tools come in handy:
- Compress images to reduce file sizes before uploading to the web
- Crop images when you need to fix the aspect ratio before resizing
- Convert formats to switch between JPG, PNG, and WebP depending on what you need
All of them work the same way. Browser-based, private, no account needed. I keep the resize tool bookmarked because I use it at least twice a week.