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image Utility • Zero-Server Privacy • 100% Client-Side

Image Resizer

Resize images to exact pixel dimensions with aspect-ratio lock, and convert between PNG, JPEG, and WebP in one step.

Overview

Resize images to exact pixel dimensions, a percentage of the source, or a common preset size, and convert between PNG, JPEG, WebP and AVIF in the same step, entirely in your browser. Aspect-ratio lock keeps proportions right, a live preview shows the encoded result before you download, upscaling is called out honestly before it softens your image, and every download is verified by its actual bytes.

How It Works

Drop an image to load it; the width and height fields fill with the source dimensions. Work in exact-pixels mode by typing a width (with aspect lock on the height follows automatically) or tapping a preset such as 1920 x 1080 or 1200 x 630, or switch to percent-of-source mode and drag a scale slider with quick taps for 25 to 200 percent. Choose the output format - PNG, JPEG, WebP, or AVIF where your browser really has an encoder - and the preview pane re-renders the actual encoded result, showing its dimensions and file size. Press Resize and Download to save a file named with the target dimensions.

Step-by-Step Usage Guide

  1. Drop the image; width and height prefill from the source.
  2. Work in exact pixels (fields or presets) or percent of source.
  3. Pick PNG, JPEG, WebP or AVIF output.
  4. Check the preview size and dimensions, then Resize and Download.

Technical Specifications & Standards

Resizing draws the source into a canvas at the target dimensions with image smoothing set to high quality, then encodes at a fixed 0.92 quality for the lossy formats; PNG ignores quality because it is lossless. Downscaling by more than two times happens in repeated halvings first, which avoids the aliasing a single giant drawImage step produces. The preview is the real encoded blob, not the source image - a deliberate fix for the common resizer trap of showing the original while the download differs. Format availability is not assumed: a tiny test encode is sniffed by magic bytes, and if the browser has no encoder for a format (AVIF in most Firefox and Safari builds, for example) that option is hidden rather than silently saving a PNG under an .avif name. Two engineered limits are visible in the interface. Dimensions accept 1 to 20000 pixels, but the live preview is skipped above a 40-megapixel pixel budget, because a canvas that large can fail or hang on many devices; the download still works at any size, and the page says so. Preview re-encodes are debounced by 200 milliseconds and guarded against out-of-order completion. When the target exceeds the source in either dimension the page shows an explicit upscaling warning, because interpolation genuinely softens detail. The size report is direction-aware: upscaling, or converting a photo to PNG, can legitimately produce a larger file, and the page tells you that rather than assuming a saving.

Targeted Use Cases

  • Producing exact hero-image dimensions a design spec requires.
  • Generating a 50-percent preview from an oversized source photo.
  • Converting a screenshot from PNG to WebP or AVIF to cut page weight.
  • Making square social crops from a non-proportional source with lock off.

Notes & Gotchas

  • Keep aspect lock on unless you specifically want to distort.
  • Watch for the upscaling warning - downscaling is where resizing shines.
  • Use PNG for sharp graphics and text, JPEG or WebP for photographs.
  • Above 40 megapixels the preview turns off by design - the download is still exact.

Frequently Asked Questions

Is the preview the real output?

Yes. The preview is generated by encoding the resized canvas exactly as the download will, so its dimensions and file size are what you get.

Why is my resized file larger than the original?

Upscaling adds pixels, and converting photos to lossless PNG increases size. The page reports the direction honestly, and shows an explicit upscaling warning; switch to JPEG or WebP for photos if you want smaller.

Why is there no AVIF option for me?

Availability is tested by encoding a sample and inspecting the resulting bytes. Browsers without an AVIF encoder hide the option instead of mislabelling PNG output as AVIF.

What is the maximum size I can resize to?

The fields accept up to 20000 by 20000 pixels. Above a 40-megapixel budget the live preview is skipped to avoid exhausting canvas memory, but the download still runs.

Does resizing remove EXIF metadata?

Yes. The canvas re-encode drops EXIF, GPS and colour-profile data, and applies the rotation flag at decode time so photos come out upright - a privacy benefit for published images.