Batch Image Resizer

What Can the Batch Image Resizer Do?

The online batch image resizer is a free tool based on the Canvas API that lets you batch resize multiple images locally without uploading them to a server. It supports three scaling modes: by pixels, by percentage, and preset sizes, with aspect ratio preservation and custom output format and quality.

Core Features

• Batch Processing: Select multiple images and resize them all at once
• Three Modes: By pixels, by percentage, or preset sizes
• Maintain Ratio: Automatically calculate aspect ratio to prevent distortion
• Multiple Formats: PNG, JPG, WebP or keep original format
• Adjustable Quality: JPG/WebP output quality 1-100
• Batch Download: Download all processed images with one click

How to Use

1. Click to select or drag and drop multiple images
2. View the selected image list
3. Choose resize mode (pixels/percentage/preset)
4. Set target size and output parameters
5. Click "Start Processing"
6. Preview results, download individually or batch

Use Cases

Case 1: E-commerce Image Processing

Batch resize product images to uniform dimensions meeting e-commerce platform requirements, such as Taobao 800×800, Amazon 1000×1000.

Case 2: Website Image Optimization

Batch downsize website images to appropriate dimensions, reducing file size and improving page load speed and user experience.

Case 3: Social Media

Batch resize photos for different social platform requirements, such as WeChat avatars, Weibo images, Instagram squares.

Technical Background

Image resizing uses resampling. Downsampling uses bilinear interpolation or Lanczos algorithm; upsampling beyond 2x typically causes blurriness. Canvas API defaults to bilinear interpolation, with imageSmoothingQuality set to high for better results. Maintaining aspect ratio is a fundamental principle to prevent distortion. JPG format suits photographs, PNG suits images with transparency, and WebP is a modern format offering both small size and good quality.

FAQ