Bulk Image Resizer

Uploading twelve-megapixel photos to a content management system or sending high-resolution product images over email wastes bandwidth and slows down every page that loads them. Most web contexts need images no wider than 1200 or 1920 pixels, yet cameras and phones produce files four to six times that size. Resizing one image at a time in an editor is manageable for a handful of photos, but when a product catalogue has 200 images or a blog migration involves thousands, the manual approach collapses under repetition.

A batch resizer that processes everything in one click and bundles the results into a ZIP eliminates the tedium entirely. The critical detail is that this tool uses the Canvas API for resizing, so no pixels leave your device. The aspect ratio of every image is preserved by fitting it within the maximum bounding box you define, which means nothing gets stretched or distorted regardless of how varied the input dimensions are.

| Feature | Detail |

| --- | --- |

| Input formats | PNG, JPG, WebP, GIF, BMP |

| Output formats | JPEG, WebP, PNG |

| Resizing method | Fit within max bounding box (aspect preserved) |

| Upscaling | Disabled — smaller images left untouched |

| Output naming | originalname-WIDTHxHEIGHT.ext |

| Delivery | Single ZIP via JSZip |

Drop multiple images onto the upload zone in any supported format.

Set the maximum width and height in pixels — each image will be scaled to fit within this box without stretching.

Choose an output format (JPEG, WebP, or PNG) and adjust the quality slider if applicable.

Click Resize to process every image using the Canvas API.

Download the resulting ZIP file and unzip it to access all resized images named with their new dimensions.

After downloading and unzipping the output, spot-check several images by opening them in an image viewer and verifying that neither dimension exceeds the maximum you set. Confirm that the aspect ratio matches the original by dividing width by height on both the source and output — the ratio should be identical. Check the file format by inspecting the extension and, for JPEG output, verify the quality by comparing file size against the original. If you set a 1920x1080 box and one of your inputs was 800x600, it should remain unchanged since upscaling is disabled.

Setting the max dimensions too small, which degrades quality on images that will be displayed at full width on larger screens.

Forgetting that upscaling is disabled — if your images are already smaller than the bounding box, they will not be enlarged.

Expecting the ZIP to preserve folder structure; the tool flattens all outputs into a single directory with dimension-suffixed names.

Choosing PNG output for photographs, which produces much larger files than JPEG at equivalent visual quality.

The tool imposes no hard file count limit — your device memory is the only constraint. A few hundred images at typical resolutions process comfortably, while very large batches may take a few seconds. The Canvas API handles the actual pixel manipulation, and JSZip assembles the output archive without any server interaction. If an input image has transparency (PNG with alpha channel) and you select JPEG output, the transparent areas will be composited against a white background since JPEG does not support alpha.

Preparing product images for an e-commerce platform that requires all uploads under 2000 pixels on the longest side.

Resizing a batch of photos from a 48-megapixel camera for use in a blog or email newsletter.

Converting a folder of PNG screenshots to JPEG to reduce total archive size before sharing with a client.

Generating thumbnail-sized versions of artwork for a portfolio gallery at consistent dimensions.

Q: Does the tool upscale small images?

A: No. The max width and height are upper bounds. Images smaller than the box are left untouched to avoid introducing blur from upscaling.

Q: How are output files named?

A: Each file uses the original base name plus the new dimensions, for example photo-1920x1080.jpg. The ZIP prevents name collisions across files.

Q: Is there a file count limit?

A: No hard limit exists. Your device memory is the practical bound. A few hundred images at typical resolutions works without issues.

Q: Why bundle results in a ZIP?

A: Downloading dozens of individual files is cumbersome. A single ZIP is faster for the browser to generate and more convenient for the user to manage.

Q: Can I lock the aspect ratio manually?

A: Aspect ratio is always preserved by default. The tool fits each image within the bounding box without stretching.

Q: What happens to transparent PNGs exported as JPEG?

A: Transparent areas are composited against a white background since the JPEG format does not support an alpha channel.

Try the Bulk Image Resizer tool. See also Image Resizer, Image Compressor, and Image Converter.