Free Online Image Resizer
Updated September 2026
Resize images to exact pixel dimensions or by percentage in your browser — set width and height with optional aspect ratio lock, then download. No upload, no account required.
Verified Capabilities
Set exact width and height in pixels, with an optional aspect-ratio lock that auto-calculates the other dimension.
Resizing happens entirely in your browser via the Canvas API — no upload, no server round-trip.
Shows original and new dimensions together once you click Resize Image.
Output is always JPEG (if the source was JPEG) or PNG for every other format — WebP, GIF, and BMP inputs are converted to PNG, not preserved in their original format.
Professional image processing once required expensive desktop software. The Image Resizer handles the same job in seconds — entirely in your browser, with no file uploads to external servers.
Resize images to exact pixel dimensions or by percentage in your browser — set width and height with optional aspect ratio lock, then download. No upload, no account required. Results are immediate — no waiting, no loading screens, no account required.
Who uses the Image Resizer?
- Social media managers resizing photos to exact platform requirements (e.g. 1080×1080px for Instagram)
- Web developers shrinking large photography assets to the maximum display size before uploading to a CMS
- E-commerce sellers standardising product image dimensions to the same square format for a consistent storefront
Common uses and search terms
The Image Resizer is frequently used for: image resize, resize photo, scale image, resize image online, change image dimensions, resize photo online, image dimensions changer, resize jpg online, resize png online, reduce image pixels, image width height. Whether you need a quick result or are working through a longer project, the tool handles all common variations without any configuration.
Why use Allio Tools's Image Resizer?
Your files never leave your device — all processing is done locally using browser JavaScript APIs. The tool is completely free with no usage limits, no premium tiers, and no account required. Available in 11 languages and optimised for all screen sizes, the Image Resizer works on desktop, tablet, and mobile with no app download needed.
See also:JPG to PNG Converter · QR Code Generator · PNG to JPG Converter
How the Image Resizer works
Drag your image onto the drop zone, or click to browse and select a file.
Enter the target Width or Height in pixels — check "Maintain aspect ratio" to lock proportions.
Adjust the other dimension or let it calculate automatically.
Click Resize Image — the resized preview appears instantly.
Click Download to save the resized image. Click Clear to start over with a new file.
Tips & tricks
- Resizing requires clicking the "Resize Image" button — the preview does not update automatically as you type new width/height values.
- With "Maintain aspect ratio" checked, changing Width automatically recalculates Height (and vice versa) — uncheck it to stretch the image to arbitrary dimensions.
- Output format is JPEG only if your original file's MIME type contains "jpeg" — every other input format (PNG, WebP, GIF, BMP) is converted to PNG on output, not preserved in its original format.
- Width and Height are capped at 8,000px each — very large dimensions may be slow or trigger memory warnings in older browsers.
Frequently Asked Questions
What image formats can I resize?
The resizer accepts all common browser-supported image formats: JPEG, PNG, WebP, GIF (first frame only), and BMP. The output is always a PNG or the same format as the original, depending on the browser's canvas export settings.
Will resizing reduce my image's file size?
Resizing to smaller dimensions reduces file size proportionally — a 2000px image resized to 1000px uses roughly one-quarter the pixels, significantly shrinking the file. However, upscaling (making the image larger) increases file size and reduces quality by stretching existing pixels.
What is the maximum output size?
The tool allows output dimensions up to 8,000 × 8,000 pixels. In practice, very large outputs may be slow or cause memory warnings in older browsers. For web use, keeping images under 2,000px wide is sufficient for most displays.
Does aspect ratio lock work for custom crops?
Aspect ratio lock keeps the original width-to-height ratio when you change one dimension. To crop to a different ratio (e.g. 16:9 from a 4:3 photo), uncheck the lock and set both dimensions independently. The image will stretch — use a dedicated crop tool for non-distorted cropping.
Is my image uploaded to any server?
No. All resizing happens entirely in your browser using the Canvas API. Your image is never transmitted to a server, and nothing is stored after you close the tab.
Is my data safe when using the Image Resizer?
Completely safe. The Image Resizer processes everything locally in your browser. No input data, results, or usage information is ever transmitted to or stored on any server.
What image formats does the Image Resizer support?
The Image Resizer works with common image formats supported by your browser, including JPEG, PNG, WebP, and GIF. SVG support varies by tool. No format conversion plugin or driver is needed.
Does the Image Resizer work with large image files?
Yes. The Image Resizer processes files entirely in your browser using the Canvas API. Very large files (over 20 MB) may take a few extra seconds on older or lower-powered devices. Closing other tabs can free up memory for better performance.
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