Image Resizer

What is Image Resizer?

Free online image resizer. Resize JPEG, PNG, WebP images to any dimension in your browser. No upload to server. Maintain aspect ratio option. Browser-based image tools — no upload to servers, all processing done locally. TekPulse's Image Resizer is completely free — no signup, no ads in results, and no data stored on our servers.

How to Use Image Resizer Online

1. Upload an image by dragging it onto the drop zone or clicking to browse
2. Enter the desired width and/or height in pixels
3. Toggle "Lock Aspect Ratio" to maintain proportions when resizing by only one dimension
4. Preview the resized image before downloading
5. Download the resized image — it is processed entirely in your browser, never uploaded

Image Resizer Formula & Calculation

When 'Lock aspect ratio' is checked, changing the width automatically recalculates height (and vice versa) using the original image's width:height ratio, preventing the stretching or squashing that happens when dimensions are set independently. The actual resizing is done by drawing the source image onto an HTML5 canvas at the target dimensions (ctx.drawImage), which uses the browser's built-in image resampling (effectively bilinear/bicubic interpolation) to compute each new pixel as a weighted blend of the nearest original pixels — this is what keeps resized images looking smooth rather than blocky.

Example: An original image at 4000×3000px resized to width 800px with aspect ratio locked computes height = 3000 × (800 ÷ 4000) = 600px, preserving the exact 4:3 ratio. The canvas is then re-exported via toBlob() at your chosen format and quality.

Key Factors That Affect Your Result

1. Aspect ratio lock — Unlocking it lets you set width and height independently, but any mismatch with the original ratio will distort the image (stretched or squeezed) — only disable it intentionally, e.g. to force a square thumbnail.
2. Output format — JPEG and WebP support a quality slider (lossy compression) for smaller files; PNG is always lossless, so the quality slider has no effect and file sizes stay larger, especially for photographic content.
3. Upscaling vs. downscaling — Downscaling (making an image smaller) generally looks sharp since you're discarding detail; upscaling (making it larger than the original) can't add detail that wasn't there and will look visibly softer or blurrier the more you enlarge it.
4. Preset sizes — Common targets like 1920×1080 (Full HD), 1280×720 (HD), and small square thumbnails match typical use cases (wallpapers, video thumbnails, profile pictures) without needing to calculate dimensions manually.

Why Use TekPulse Image Resizer?