Upload an image and resize it to custom dimensions.
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What is the Image Resizer?
An image resizer is a tool that changes an image's pixel dimensions (width and height) while maintaining quality through resampling. It mathematically interpolates pixels to either reduce the image size (downsampling) or enlarge it (upsampling). Resizing differs from cropping because the whole image is preserved—nothing is cut out—and the aspect ratio can be locked or changed freely depending on your needs.
How it works
When you upload an image, the resizer reads its current dimensions and colour data. You specify new dimensions—either exact pixels, a percentage scale, or by locked aspect ratio. The tool then applies an interpolation algorithm (usually bicubic or bilinear) to blend existing pixels into the target grid. For smaller outputs, multiple pixels are averaged; for larger outputs, colours are estimated between existing pixels. The result is resampled image data, which is then encoded back into your chosen format (JPG, PNG, WebP, etc.) and ready to download.
Examples
Input
Result
Notes
Original: 3000×2000 px JPG; target: 1200×800 px
Output: 1200×800 px JPG (40% of original size, ~50 KB if original was ~500 KB)
Common for web use. Smaller file size loads faster; quality remains sharp at this scale.
Original: 800×600 px PNG; target: 400×300 px with locked aspect ratio
Aspect ratio lock ensures no stretching or distortion; useful for thumbnails or consistent layouts.
Original: 600×400 px; target: 120% scale
Output: 720×480 px (scaled by 20% larger)
Scaling by percentage is quicker than calculating new pixel dimensions manually, especially for batch jobs.
How to use the Image Resizer
Upload your image (JPG, PNG, WebP, GIF, etc.) by clicking the upload area or dragging it in.
Enter your target width and height in pixels, or select a preset (Instagram, Twitter, email header, etc.).
Toggle 'Lock Aspect Ratio' if you want proportions to scale automatically and avoid stretching.
Choose output format and quality (JPG quality 80–90% is a good balance of file size and visual quality).
Click 'Resize' and the tool processes your image instantly.
Download the resized image or copy it to clipboard if your tool supports it.
Benefits
No software installation—works entirely in your browser on any device.
Batch resize multiple images at once by uploading them together.
Preserve or adjust aspect ratio to avoid distortion or force square/specific shapes.
Reduces file size dramatically; a 3000×2000 px photo typically shrinks from 2–5 MB to 100–300 KB when resized to 1200×800 px.
Instant preview before download so you can adjust dimensions without re-uploading.
Supports all common formats (JPG, PNG, WebP, GIF) and lets you convert during resize.
Tips & common mistakes
Common mistakes
Upsampling (enlarging) small images too much; quality degrades noticeably above 150% scale. Always start with high-res originals.
Forgetting to unlock aspect ratio when the target dimensions differ; the image stretches weirdly if forced into wrong proportions.
Choosing maximum JPG quality (100%) when 80–85% is visually identical but half the file size; over-quality wastes bandwidth.
Resizing once then re-resizing multiple times; each resampling adds blur. Do final resize in one step from the original.
Tips
For web, aim for max dimension 2560 px; most users' screens won't show sharper detail, and file sizes stay manageable.
When uploading to social media, check platform specs first: Instagram square posts are 1080×1080 px, story is 1080×1920 px, feed carousel is 1080×1350 px.
JPG is best for photos; PNG for graphics and transparency; WebP for web (25–35% smaller than JPG at same quality).
If your tool has a 'smart crop' or 'face-aware' resize, enable it for portraits—prevents heads from being cut if aspect ratio changes.
Frequently asked questions
Why does my image look blurry after resizing?
Upsampling (enlarging) a small image causes blur because the tool must guess colours for new pixels. Always resize from a large original image. If you must enlarge, use 'Smart Sharpen' or a tool designed for upsampling.
What's the best quality setting for JPG?
80–85% quality is imperceptible to the human eye but cuts file size in half vs. 100%. Use 90% if you need extra sharpness (e.g. product photos); use 70% only for thumbnails or previews.
Should I resize before or after cropping?
Crop first to remove unwanted areas, then resize. This ensures you're resizing only the final composition and not wasting pixels on unwanted edges.
Can I resize GIFs or videos?
Static GIFs yes; animated GIFs and videos require different tools that preserve frame sequences. Some batch resizers handle animated GIFs if they keep all frames.
What does 'lock aspect ratio' mean?
When locked, if you change width, height auto-adjusts to match the original proportions. Unlocked lets you set any width/height freely, which may stretch or squash the image.
Can I batch resize 100 images at once?
Most browser-based tools handle 5–20 at once before slowing down. For bulk jobs (100+), use desktop software like ImageMagick (command line) or Lightroom (GUI), or upload to a service with batch queueing.