Batch Image Resize

Proportional scaling scales by percentage or longest/shortest edge constraints, automatically maintaining original aspect ratio so images won't distort. For example, setting longest edge to 800px, the tool automatically calculates the other dimension to scale the image proportionally without exceeding 800px on the longest edge. Specifying exact dimensions directly sets target width and height, with option to lock aspect ratio. When locked, scales proportionally to maximum range within target dimensions; when unlocked, forces stretching to exact dimensions which may cause distortion. We generally recommend using proportional scaling or dimension specification with locked aspect ratio.

Theoretically there's no hard quantity limit, but actual processing capability is affected by device memory and performance. Generally, home computers can smoothly process dozens of images, and better-performing devices can handle hundreds. Since all processing completes in the browser locally, image data occupies local memory. We recommend keeping single batch processing within 50 images for optimal experience. If you have particularly large image quantities, process in batches to avoid browser lag or crashes. Processing speed is typically several to dozens of images per second, depending on image resolution and device performance.

Built-in common size presets include e-commerce main image (800x800), social square (1080x1080), landscape image (1920x1080), thumbnail (400x400), portrait image (1080x1920), etc., covering mainstream use scenarios. Each preset is labeled with applicable platform and scenario for quick selection. If presets don't meet requirements, you can also customize any width and height values to flexibly handle special size requirements. Preset sizes are periodically updated based on mainstream platform specifications to ensure coverage of the latest size standards.

Proportions are maintained by default. In proportional scaling mode, aspect ratio is automatically locked - just specify one dimension (width or height) or set longest/shortest edge constraints, and the other dimension calculates automatically so images won't distort. In specify exact dimensions mode, aspect ratio is also locked by default, scaling proportionally to maximum range within target dimensions. If you need to force stretch to exact dimensions, you can manually unlock aspect ratio, but this may cause image distortion. We generally recommend keeping aspect ratio locked to ensure visual quality, avoiding distortion effects on image quality.

Two download methods are provided. First, individual download - click each image's download button to save separately, suitable for scenarios requiring selective saving of some images. Second, package as ZIP file for one-time download of all - all resized images will be packaged into one ZIP archive, and after downloading, extract to get all images. Resized images maintain original filenames unchanged, convenient for matching in projects. Package download is especially suitable for processing large quantities of images, avoiding the tedious operation of saving one by one.

Downscaling usually doesn't noticeably affect quality because it's scaling from high resolution to low resolution with redundant pixel information. Upscaling may cause quality reduction because interpolation algorithms need to generate new pixels - the larger the magnification, the more obvious. The tool uses high-quality bilinear or Lanczos resampling algorithms to maintain quality as much as possible during scaling. For lossy formats like JPG, re-encoding will bring slight quality loss. We recommend choosing higher quality parameters when resizing to reduce loss. Lossless formats like PNG won't lose quality after resizing and re-encoding.