Image Resize Tool

Aspect ratio is the width-to-height relationship (e.g., 16:9, 4:3, 1:1). "Maintain Ratio" mode: when you change the width, the height adjusts automatically to preserve the original proportions — the image scales uniformly and is never distorted. "Free Resize" mode: you can set width and height independently, which can stretch or squish the image. Use Free Resize when you specifically need a non-proportional output (e.g., a square crop from a landscape image), but expect distortion unless the proportions happen to match the original.

When you resize an image to larger dimensions than the original (upscaling), the tool must invent pixels that do not exist in the source. Canvas API's default bicubic interpolation smooths between neighboring pixels, which produces a blurry result at significant enlargements. There is no way to fully recover detail that was never captured. General rule: resize down to save space, resize up only by 10-20% if necessary. For significant enlargements, use AI upscaling tools (like Real-ESRGAN or Topaz Gigapixel) that use machine learning to intelligently synthesize detail.

DPI (Dots Per Inch) is a print concept — it describes how densely pixels are packed when printing. For web and screen display, DPI is irrelevant because screens display at native pixel dimensions regardless of the DPI metadata in the file. This tool resizes to pixel dimensions; DPI metadata in the output depends on the browser's Canvas encoder (usually 72 or 96 DPI). For printing, what matters is: total pixels ÷ print size in inches = DPI. A 300 DPI print at 4×6 inches needs 1200×1800 pixels. Resize to the required pixel count, then set DPI metadata in Photoshop or GIMP if your print shop requires it.

Input: JPEG (.jpg/.jpeg), PNG (.png), and WebP (.webp). You can choose the output format independently — upload a PNG and save as JPEG, or upload JPEG and save as WebP. Format conversion considerations: JPEG to PNG increases file size (PNG is lossless); PNG with transparency to JPEG loses transparency (becomes white); PNG or JPEG to WebP typically reduces file size while maintaining quality. Choose "Keep Original Format" to output in the same format as the uploaded file.

4000x4000 pixels. This covers most practical use cases including high-DPI screen displays, large print formats at 150 DPI, and web banners. Upscaling to 4000px from a small source image will produce a blurry result. For genuinely large-format print (posters, billboards), start with a high-resolution source image that is already close to the needed pixel dimensions.

Resize when: the image dimensions are larger than they will ever be displayed (a 4000x3000 photo displayed in a 800px wide column is serving 25x more pixels than needed). Compress when: the dimensions are appropriate but the file size is too large due to high quality settings. Often you need both: resize to appropriate display dimensions first, then compress to target file size. For web images: resize to maximum display width (typically 1200-1920px for full-width) then compress to 100-300KB target.

No. All resizing happens in your browser using the HTML5 Canvas API. Your images never leave your device. This applies to the upload, the resize processing, and the download — all are local operations.