Image Resizer
Resize images by pixels or percentage in your browser — lock the aspect ratio, pick your format, and download instantly. No upload, no sign-up.
About this tool
Change image dimensions effortlessly. Drop any image, pick pixels or percentage, lock the aspect ratio, choose JPEG/PNG/WebP output, and download the result — all in your browser, no files ever leave your device.
How to use it
Quick steps to get the most out of this utility.
- 1
Upload your image
Drag and drop or click to browse. Supports JPG, PNG, WebP, GIF, BMP, and AVIF up to 50 MB.
- 2
Set dimensions
Choose Pixels or Percent mode. Enter width/height or pick a preset (50%, 75%, 100%, 150%, 200%).
- 3
Pick format and quality
Keep the original format or convert to JPEG, PNG, or WebP. Adjust quality for JPEG/WebP output.
- 4
Download
Click Resize Image, then download your resized file. See original vs. new dimensions and file size.
Why image resizing matters
Every website, social platform, and app has specific dimension requirements for images. Uploading an oversized photo wastes bandwidth and slows load times — a 5472 × 3648 iPhone shot is 20 megapixels, but most web layouts need only 1920 px wide. Conversely, upscaling a tiny thumbnail destroys sharpness. This tool lets you set any target dimension, lock the aspect ratio so nothing looks stretched, and choose the resampling algorithm that best preserves quality.
As a concrete example: a 5472 × 3648 JPEG from a smartphone (roughly 3.5 MB) resized to 1920 × 1280 with Lanczos3 resampling produces a 280 KB file — 92% smaller — with no visible quality loss when displayed on a website. The same image resized to 50% (2736 × 1824) still looks crisp and weighs just 900 KB, making it ideal for email attachments or blog posts.
Resize vs. resample — what is the difference?
Technically, resizing changes an image's pixel dimensions, while resampling determines how the new pixel values are computed. Every resize operation involves resampling — you cannot change pixel count without deciding how to fill in or discard pixels. This tool uses Lanczos3 resampling, which examines a 3×3 neighborhood around each pixel to compute the output. Compared to naive bilinear or nearest-neighbor interpolation, Lanczos3 preserves edges, reduces aliasing, and produces results comparable to desktop software like Photoshop or GIMP — with no quality compromise.
The tool also applies an unsharp mask (amount 80, radius 0.6, threshold 2) after downscaling to counteract the natural softening that occurs when pixels are averaged together. The result is sharper, more detailed output than most browser-based resizers that skip this step.
Why no-upload matters for image resizing
Photos you resize often contain personal content — family faces, home interiors, ID documents, private screenshots, or medical records. Upload-based resizers send your original file to a remote server for processing, and you have no audit trail, no retention guarantee, and no way to verify the file was deleted afterward. This tool runs entirely inside your browser tab. Zero bytes of your image leave your device. The JavaScript code runs locally, produces the resized file, and streams it straight to your download folder.
| Feature | This tool | Upload-based tools |
|---|---|---|
| Privacy | 100% client-side | Images sent to a server |
| Speed | Instant (no upload) | Upload + process + download |
| Data retention risk | None | Server logs, CDN caches |
| Resampling quality | Lanczos3 + unsharp mask | Varies (often bilinear) |
Frequently asked questions
Is my image uploaded to a server?+
No. The entire resize runs in your browser using JavaScript. Your image never leaves your device, never touches our servers, and is never logged or stored anywhere.
What image formats are supported?+
JPG, PNG, WebP, GIF, BMP, and AVIF. The tool auto-detects the format — just drop any image file. You can also choose the output format (JPEG, PNG, or WebP) regardless of the input format.
What is the maximum file size?+
You can resize images up to 50 MB. Files over 25 MB will show a warning since processing may be slower on mobile devices due to memory limits per browser tab.
Will this work on mobile?+
Yes, on modern mobile browsers (Chrome, Safari, Firefox). Very large images (>25 MB) may be slower on phones due to per-tab memory constraints. For best results on mobile, resize to a smaller dimension first.
What is the difference between resizing and resampling?+
Resizing changes the pixel dimensions (width and height) of an image. Resampling is the algorithm that determines how new pixel values are calculated. Every resize involves resampling — this tool uses Lanczos3, which looks at a 3×3 neighborhood of pixels to produce the highest-quality output, significantly better than basic bilinear or nearest-neighbor methods.
What quality does Lanczos3 resampling give?+
Lanczos3 is a high-quality resampling filter that preserves sharpness, reduces aliasing, and minimizes visual artifacts. It is the same algorithm used in professional tools like Photoshop. You get crisp edges, smooth gradients, and no visible pixelation — even when downscaling by more than 50%.
Can I unlock the aspect ratio to stretch or squash the image?+
Yes. By default the aspect ratio is locked so your image stays proportional. Click the lock icon (🔗) to unlock it, then set any width and height independently. Lock it again to return to proportional scaling.
Does the resize tool work on phones and tablets?+
Yes. The tool runs entirely in your browser using Web Workers, so it works on any modern phone or tablet. For very large source images (e.g. 8000×6000), the processing time will be longer on lower-powered devices. Setting a smaller target dimension helps.
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