High-quality resampling
Uses the browser's smooth, high-quality resampling so downscaled images stay crisp rather than jagged or moiré-patterned.
Image Resizer
Resize images by pixel dimensions or percentage, with aspect lock.
- Upload
- Batch upload supported · 25 MB max
- Privacy
- Nothing is uploaded
- Cost
- Free · no sign-up · no watermark
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The tool is loading its code on your device. This happens once and is cached for later visits.
Processed entirely on your device
Your file is read, transformed and re-encoded inside this browser tab using JavaScript. There is no upload endpoint — nothing leaves your machine, nothing is stored, and the result is created as a local object URL that disappears when you close the page.
Overview
About the Image Resizer
Change an image's width and height in pixels or percent, keep the aspect ratio locked, and export as PNG, JPG or WebP. Batch resize up to 20 files locally.
Resizing is the least glamorous and most impactful thing you can do to an image. Before any clever compression, matching the pixel dimensions to the actual display size removes the bulk of wasted bytes — and it is the step most people skip because their camera or screenshot tool produces whatever size it feels like.
Pixel dimensions, DPI and why DPI does not matter here
A common source of confusion: a "300 DPI" image and a "72 DPI" image with the same pixel dimensions contain exactly the same amount of data. DPI is a print instruction that tells a printer how densely to place those pixels on paper. For screens, only the pixel count matters. This resizer works in pixels, which is what every web, app and social platform actually consumes.
If you are preparing for print, work out the physical size you need and multiply by the target DPI: an A4 page at 300 DPI is roughly 2480 × 3508 pixels.
Presets and when to use them
- Social square (1080×1080) — Instagram feed, LinkedIn posts, product thumbnails.
- Story / reel (1080×1920) — vertical full-screen formats.
- Profile (400×400) — avatars; most platforms downscale aggressively so 400 is plenty.
- Email header (600–1200 wide) — email clients cap layout width around 600 CSS pixels.
- HD (1920×1080) and 4K (3840×2160) — video thumbnails and full-screen backgrounds.
Aspect ratio, and when to break the lock
Leave the lock on almost always. Unlocking it stretches the image, and human faces and product proportions are the first things to look wrong. The legitimate exceptions are deliberate design effects, or fitting an image into a fixed container where you accept distortion — in which case CSS object-fit: cover with a crop is nearly always the better solution.
Upscaling honestly
Browsers upscale by interpolation: they estimate new pixel values from their neighbours. The result is smooth but soft, and no amount of sharpening restores detail that was never captured. If you must enlarge, do it in modest steps (no more than 150–200% at a time) and expect a painterly result rather than a crisp one.
Step by step
How to use the Image Resizer
Upload the image or images you want to resize.
Enter a new width or height in pixels, choose a preset, or switch to percentage mode.
Keep the aspect-ratio lock on unless you deliberately want to stretch the image.
Choose an output format and press Resize.
Check the new dimensions and download.
Why use it
Benefits and common use cases
What this tool is good for, and what it deliberately does not try to do.
Aspect ratio protection
The lock is on by default, so entering one dimension calculates the other. Distorted, stretched images are the most common resizing mistake and this prevents them.
Presets for real targets
One-click sizes for social posts, profile pictures, thumbnails, email headers and 4K/1080p — the dimensions people actually search for.
Never upscale blindly
Enlarging beyond the original resolution is flagged, because it adds pixels that contain no new information and only softens the result.
Questions
Frequently asked questions
Short, honest answers about quality, limits and privacy.
What is the difference between resizing and cropping?
Resizing scales the whole image so everything stays in frame but each element becomes smaller or larger. Cropping removes part of the image to change its shape. To fit a square avatar from a landscape photo you need to crop; to make a large photo web-friendly you need to resize.
Does resizing reduce image quality?
Downscaling discards pixels, so some fine detail is irrecoverably lost — but the remaining image is still sharp. Upscaling is the opposite problem: the browser interpolates new pixels from surrounding ones, which produces a soft, slightly smeared result.
What size should I resize images to for a website?
Match the widest container the image appears in, multiplied by two for high-density displays. A 700-pixel content column needs about 1400 pixels; a full-width hero needs 1920–2560. Anything larger is bandwidth you are paying for and never showing.
Can I resize by percentage?
Yes. Percentage mode is useful for making a whole set proportionally smaller — for example 50% halves both dimensions and quarters the pixel count, which typically cuts file size dramatically.
Will transparency be preserved?
If you export to PNG or WebP, yes. Exporting to JPG flattens transparent areas onto the background colour you choose, because the JPEG format has no alpha channel.