Quick answer: batch resize images online
To batch resize images online, drop the whole set into a browser-based resizer, choose percentage scaling or exact pixel dimensions, keep aspect ratio locked, then download the resized copies together as a ZIP. That is the safest workflow for store photos, blog images, form uploads, documentation screenshots, and social drafts because every file gets the same rule instead of being edited one by one.
The important part is choosing the rule before you click resize. A folder of 4032 x 3024 phone photos for a blog usually needs a shared width, such as 1600 px. A folder of product thumbnails may need a square crop first, then an 800 px export. A set of email attachments may only need 50% scaling so the files are easier to send. Those are different jobs, even though people describe all of them as "make these images smaller."
PhotoTools runs the resize in your browser, so the images do not need to be uploaded to a server first. You can resize a mixed batch, keep the original formats, or export the batch as JPG, PNG, WebP, or AVIF.
Start with the destination, not the file size
The best resize target is based on where the image will be used. If a 4000 px wide image appears in a 700 px content column, the extra pixels slow the page down without making the reader see more detail. If the same image is used as a full-bleed hero on a large desktop screen, a 700 px export will look soft.
Use this table as a practical starting point:
| Destination | Practical resize target | Notes |
|---|---|---|
| Blog or help-center image | 1200 to 1600 px wide | Good for most article columns and retina displays |
| Full-width hero image | 1920 to 2400 px wide | Use a wider export only when the layout really displays it that large |
| Product grid thumbnail | 600 to 1000 px on the long edge | Crop to a consistent shape first if the grid requires square cards |
| Email attachment | 1024 to 1600 px on the long edge | Small enough to send, still readable on common screens |
| Form or portal upload | Match the stated pixel requirement | If the site gives exact width and height, follow that spec |
| Social post or link preview | Match the required aspect ratio first | Crop for the shape, then resize for the platform |
| Documentation screenshot | 1200 to 1600 px wide | Keep text legible; avoid heavy JPG compression on UI screenshots |
If you do not know the exact destination yet, make two exports: one larger web version around 1600 px wide and one small thumbnail version around 600 to 800 px. Keep the untouched originals in a separate folder so you can create another size later.
Percentage scaling vs exact pixel dimensions
PhotoTools gives you two resize modes: percentage and dimensions. They solve different problems.
Use percentage scaling when the source images are different sizes and you want all of them smaller by the same amount. For example, a wedding folder might include portrait photos, landscape photos, and a few cropped details. Resizing everything to 50% keeps each image's original shape while cutting the pixel count sharply.
Use exact pixel dimensions when the destination has a known requirement. For a blog, entering 1600 in the width field and leaving height blank is usually cleaner than forcing every image to a fixed width and height. With aspect ratio locked, each image keeps its shape and the height is calculated automatically.
Be careful with exact width plus exact height. If you enter both dimensions while the images have different shapes, the tool may need to stretch or squeeze the pixels if the ratio does not match. For consistent square product images, crop to square first, then resize to 800 x 800. For mixed editorial photos, set one dimension and let the other follow.
How to batch resize PNG, JPG, WebP, and AVIF files
Here is the clean workflow inside PhotoTools:
- Open the resize tool.
- Drop the files into the upload area. You can add multiple images at once.
- Choose Percentage for proportional scaling or Dimensions for pixel targets.
- If you use dimensions, keep the link icon enabled so the aspect ratio stays locked.
- Choose the output format: same format, JPG, PNG, WebP, or AVIF.
- Click Resize all.
- Download individual files or use the ZIP button when the batch is done.
For a typical website cleanup, I would use dimensions, set width to 1600, leave height empty, keep aspect ratio locked, and export photos as WebP or JPG. For transparent logos, screenshots with sharp edges, or graphics that already use flat colors, I would keep PNG unless file size becomes a problem.
Keep aspect ratio locked unless you are deliberately changing shape
Aspect ratio is the relationship between width and height. A 4000 x 3000 photo has a 4:3 ratio. A link preview image may use a wider shape. A product thumbnail grid might require a square.
Resizing changes size, not composition. If you force a 4:3 image into a square by changing only dimensions, the image can look stretched. That is why the aspect-ratio lock matters. Enter one dimension, let the other calculate itself, and the photo keeps its natural proportions.
When the final destination needs a different shape, do the job in two steps:
- Crop first to the required ratio, such as square, portrait, or landscape.
- Resize the cropped copy to the final pixel size.
That small ordering detail is the difference between a clean product grid and a batch of distorted images.
Resize, compress, or convert: which one do you actually need?
People often use "resize" to mean any kind of file reduction, but three separate operations are involved.
| Job | What changes | Best for | Example |
|---|---|---|---|
| Resize | Pixel width and height | Making an image fit a layout or upload spec | 4032 px wide to 1600 px wide |
| Compress | File data or visual quality | Hitting a KB limit after dimensions are right | 1.2 MB to under 200 KB |
| Convert | File format | Browser support, transparency, or file-size strategy | PNG to WebP, HEIC to JPG |
Resize first when the image is far larger than it will be displayed. Compression should come after resizing if a site says the file must be under a certain limit, such as 200 KB. Converting format helps when the destination prefers one format over another, but it does not replace choosing the right dimensions.
Choosing the output format after resizing
The output format should match the content of the image and the place it will be used.
| Output format | Use it for | Watch out for |
|---|---|---|
| Same format | Quick batches where the current file types already work | Keeps old format choices, even if they are not ideal |
| JPG | Photos, listings, email attachments, broad compatibility | No transparency; repeated saves can soften details |
| PNG | Logos, UI screenshots, transparency, sharp edges | Can be large for photos |
| WebP | Modern websites and image-heavy pages | Older workflows or CMS tools may not accept it |
| AVIF | Aggressive file-size reduction on modern web projects | Slower encoding and weaker support in older tools |
For iPhone HEIC or HEIF files, do a quick test before processing a large batch. Some browsers can preview or decode them, and some cannot. If a HEIC file fails during resizing, convert it to JPG first, then run the batch resize.
A folder workflow that stays organized
Batch work gets messy when every export lands in the same download folder with similar names. A simple naming system helps.
Create a folder structure like this before you start:
product-photos/
originals/
web-1600w/
thumbs-800w/
upload-under-200kb/
Keep the camera originals in originals/. Run one batch for the large web version and another for thumbnails. If the site also has a strict KB limit, compress the already-resized files into the upload folder.
For filenames, keep the subject first and add the size at the end:
linen-shirt-blue-original.jpg
linen-shirt-blue-1600w.webp
linen-shirt-blue-thumb-800.jpg
That is boring in the best possible way. Six months later, you will know which file is the master and which one was made for the site.
How large should the batch be?
Because browser resizing runs locally, there is no upload queue waiting on a remote server. The limit is the memory available in your browser and device. A modern laptop can usually handle dozens of ordinary photos, but very large phone images, PNG screenshots, and AVIF exports can consume more memory than expected.
For a real folder, test three to five images first. Check the dimensions, file size, and sharpness. If the result is right, process the rest in groups of 50 to 100. For huge folders, smaller batches are easier to recover if one unusual file fails.
Do not close the tab until the ZIP has downloaded. The originals stay on your device, but the resized outputs exist in browser memory until you save them.
Quality check before uploading
Before you replace images on a website, store, or form, check a small sample:
- Open one resized photo at 100% zoom and make sure it is not blurry.
- Confirm the width and height match the destination.
- Check that transparent PNG logos still have transparency.
- Make sure screenshots with text are readable.
- Confirm the file extension matches the format the destination accepts.
- Upload one test image before processing the entire folder.
For websites, also check the page where the image appears. A file can be technically correct and still look wrong if the crop fights the layout.
Never scale small images up unless you have no choice
The PhotoTools percentage control can go above 100%, and dimensions mode can create a larger file than the original. That does not mean upscaling restores detail. Enlarging a small image forces the browser to invent pixels, which usually makes faces, text, and product edges look soft.
If a platform rejects an image because it is too small, look for the original camera file, export from the design source again, or use a dedicated upscaling workflow. For normal batch resizing, the best results come from starting large and resizing down.