liminfoImage Resizer
Free web tool: Image Resizer
Drop a file here, or
Choose fileJPG, PNG, WebP image files (max 50MB)
About Image Resizer
The Image Resizer tool lets you change the pixel dimensions of any image directly in your browser. Enter a target width and height in pixels, and the tool uses the HTML5 Canvas API drawImage() method to scale the image to your exact specifications. An optional aspect ratio lock automatically calculates the corresponding dimension when you change one value.
The tool reads the original image dimensions using naturalWidth and naturalHeight properties, then creates a canvas at the target resolution and draws the scaled image with ctx.drawImage(img, 0, 0, width, height). The bilinear interpolation algorithm built into the browser Canvas rendering produces smooth downscaling and upscaling results.
It supports JPG, PNG, and WebP images up to 50MB. The resized output preserves the original format (JPEG maintains JPEG, others become PNG) via canvas.toBlob(). A side-by-side preview shows the original and resized versions, and the download filename includes the new dimensions (e.g., resized_800x600.png).
Key Features
- Resize images to exact pixel dimensions by entering custom width and height values
- Aspect ratio lock that auto-calculates height when width changes and vice versa
- Canvas API drawImage() with browser-native bilinear interpolation for smooth scaling
- Displays original image dimensions (naturalWidth x naturalHeight) for reference
- Side-by-side preview comparing original and resized images with dimension labels
- Preserves JPEG format for JPEG inputs and PNG for all other formats on download
- Download filename includes target dimensions (e.g., resized_1024x768.jpg)
- Supports JPG, PNG, WebP images up to 50MB with drag-and-drop file upload
Frequently Asked Questions
How does the aspect ratio lock work?
When the aspect ratio lock is enabled, changing the width automatically recalculates the height using the formula: newHeight = Math.round((newWidth / originalWidth) * originalHeight), and vice versa. This preserves the original proportions and prevents image distortion.
What scaling algorithm is used?
The tool uses the browser built-in Canvas 2D rendering, which applies bilinear interpolation by default when calling ctx.drawImage() with different source and target dimensions. This produces smooth results for both upscaling and downscaling operations.
Can I resize an image to a larger size?
Yes, you can enter dimensions larger than the original. The Canvas drawImage() method will upscale the image using interpolation. However, upscaling beyond 2-3x the original size may produce blurry results since no new detail information is created.
Does resizing affect image quality?
Downscaling reduces pixel count, which inherently loses some detail but produces a smaller file. The Canvas bilinear interpolation minimizes artifacts. If you download as PNG, no compression artifacts are added. JPEG downloads use the browser default quality (typically ~92%).
What is the maximum file size supported?
The tool supports images up to 50MB. All processing happens locally in your browser using the Canvas API, so there is no server upload limit. Very large images may use more browser memory during canvas rendering.
Are my images sent to a server?
No. Everything runs client-side. The image is loaded via URL.createObjectURL() from your local file, resized on an HTML5 Canvas, and the result stays in browser memory. No data leaves your device.
Can I resize to specific social media dimensions?
Yes, you can enter any custom pixel dimensions. Common social media sizes include 1080x1080 (Instagram square), 1200x630 (Facebook/Twitter link preview), 1920x1080 (YouTube thumbnail), and 800x800 (product photos). Disable aspect ratio lock to use non-proportional dimensions.
What output format is used for the resized image?
The tool preserves the original format: JPEG inputs produce JPEG output (via canvas.toBlob with image/jpeg MIME type), while PNG, WebP, and other formats produce PNG output. The download filename reflects the new dimensions, e.g., resized_800x600.png.