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Image Resizer

Resize images to exact dimensions in your browser. Supports PNG, JPG, and WebP output. Maintains aspect ratio optionally. No upload — files stay on your device.

Drop an image here or click to browse

PNG · JPG · WebP · GIF · BMP

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Image resizing is the process of resampling an image to a different pixel dimension. When reducing dimensions (downscaling), multiple source pixels are combined into each output pixel using an interpolation algorithm. The browser's Canvas API uses bilinear interpolation for drawImage() operations, which balances quality and performance for typical web image sizes. Upscaling interpolates new pixels between existing ones, which softens the image; downscaling generally produces sharper results.

Web performance depends heavily on serving images at the appropriate resolution. An image displayed at 800×600 pixels but stored at 4000×3000 pixels transfers 25 times more data than necessary. Google PageSpeed Insights and Lighthouse's 'Properly size images' audit penalizes pages that serve oversized images. Resizing images to their display dimensions before upload reduces page weight and improves Core Web Vitals metrics, particularly Largest Contentful Paint (LCP).

This tool resizes images in the browser using the HTML Canvas API — drawImage() scales the source to the target dimensions during rendering, and toBlob() exports the result at the requested quality and format. The aspect ratio lock calculates the missing dimension automatically when only one is specified, preventing unintentional stretching. Output formats include PNG (lossless), JPG (lossy, smaller for photos), and WebP (modern, 25–34% smaller than JPG at equivalent quality).

Common Use Cases

Optimizing images before uploading to websites and CMSes

Photos from modern smartphones and DSLR cameras are typically 12–48 megapixels (4000–8000 pixels wide), but most web pages display images at 400–1200 pixels wide. Uploading the full-resolution original wastes storage and bandwidth. Resizing to the display width before upload reduces file size by 80–95% for typical photos. This is the single most impactful image optimization step for web performance, reducing both storage costs and page load times.

Creating correctly sized social media images

Each social media platform enforces specific image dimension requirements: Instagram posts are 1080×1080 (square) or 1080×1350 (portrait); Twitter/X cards are 1200×628; LinkedIn company posts are 1200×627; Facebook Open Graph images are 1200×630. Resizing a source photo to the exact required dimensions prevents platform auto-cropping from cutting out important content and ensures the image displays sharply at its intended size.

Generating thumbnails and preview images from originals

Content management systems, image galleries, and e-commerce platforms serve different image sizes for different contexts: large originals for detail views, medium sizes for listing pages, and small thumbnails for grid views. When a CMS doesn't automatically generate thumbnails, manually resizing originals to thumbnail dimensions produces the small preview images needed for fast-loading gallery pages and product grid displays.

How to Use

  1. Drop or click the upload area to open an image from your device.
  2. Enter the desired width and/or height in pixels.
  3. Enable Lock Aspect Ratio to automatically adjust the other dimension proportionally.
  4. Select the output format — PNG for lossless quality, JPG for smaller file size, WebP for modern browsers.
  5. Click Download to save the resized image. No files are uploaded to any server.

Common Image Dimensions

Format Comparison