Resize images by dimensions or percentage in your browser. Preserve aspect ratio, convert JPG, PNG or WebP, and download instantly.
Use this free online Image Resizer & Compressor directly in your browser. No signup required, no data leaves your device. Part of Utilier — a collection of 133+ developer utilities.
What is Image Resizer & Dimension Converter?
An image resizer changes the pixel dimensions of an image (width × height). This tool resizes JPG, PNG, GIF, and WebP images entirely in the browser using HTML5 Canvas. Upload an image, set target dimensions (pixels or percentage), maintain aspect ratio or resize freely, and download the resized result. Common uses include reducing file size for web use, creating thumbnails, or fitting images to specific dimensions for platforms (social media, print).
Pixel or percentage-based resizing: Set exact dimensions in pixels (e.g., 800×600) or resize by percentage (50% = half the original size).
Aspect ratio lock: Maintain original proportions (width:height ratio) to avoid distortion. Set width, height auto-adjusts, or vice versa.
Free resize: Unlock aspect ratio to stretch or squash images to any dimensions. Useful for fitting specific layouts.
Quality control: For JPG output, set compression quality (0-100%). Higher quality = larger file, better image. Lower = smaller file, more compression artifacts.
Format conversion: Resize and convert formats simultaneously (JPG→PNG, PNG→WebP, etc.). Output as PNG, JPG, or WebP.
Why use image resizer?
Images from cameras or design tools are often too large for web use (multi-megabyte files, 4000×3000 pixels). Resizing reduces file size and improves load times.
Reduce file size for web: Large images slow down websites. Resize to 1920×1080 or smaller for hero images, 800×600 for blog images, 400×400 for thumbnails.
No installation required: No need for Photoshop, GIMP, or desktop resizers. Works instantly in the browser on any device.
100% private: Images are processed entirely in the browser using Canvas API. No upload to servers. Safe for personal or confidential images.
Maintain quality: Unlike online resizers that re-compress heavily, this tool lets you control quality. PNG output is lossless for graphics.
Fast and simple: Upload, set dimensions, download. No complex UI or features you do not need. Perfect for quick resizes.
Mobile-friendly: Works on phones and tablets. Resize photos from your camera roll before sharing or uploading.
When to use image resizer
Use whenever you need to change image dimensions.
Optimizing images for web pages to reduce file size and improve load times.
Creating thumbnails (small preview images) for galleries or e-commerce product listings.
Reducing image dimensions before uploading to email or messaging apps (avoid attachment size limits).
Generating multiple sizes from one image (original + thumbnail + mobile version).
Downscaling high-resolution photos from cameras (24MP → web-friendly 2MP).
Preparing images for print at specific dimensions (300 DPI for print quality).
How to use image resizer
Upload an image, set target dimensions, download the resized result.
Upload an image: Click 'Upload Image' or drag and drop a JPG, PNG, GIF, or WebP file. The original dimensions are displayed (e.g., 3000×2000 pixels).
Set target dimensions: Enter width and/or height in pixels (e.g., 800×600). Or use percentage (50% = half size). Original dimensions are shown for reference.
Lock or unlock aspect ratio: With aspect ratio locked, changing width auto-adjusts height (and vice versa) to maintain proportions. Unlock for free resize.
Adjust quality (JPG only): For JPG output, set compression quality (0-100%). 80-90% is a good balance between file size and quality. PNG output is always lossless.
Preview the resized image: See the resized image before downloading. Check that dimensions and quality are correct.
Download the resized image: Click 'Download' and choose format (PNG, JPG, WebP). The resized image downloads with new dimensions.
Key features
Pixel-precise dimensions: Set exact width and height in pixels. See live dimensions as you adjust.
Percentage-based resizing: Resize by percentage (50%, 75%, 200%). Quick scaling without calculating pixels.
Aspect ratio lock/unlock: Maintain proportions to avoid distortion, or unlock to fit specific layouts.
Quality control (JPG): Set compression quality 0-100%. Balance file size vs. image quality.
Format support: Upload JPG, PNG, GIF (first frame), WebP. Download as PNG (lossless), JPG (lossy), or WebP.
100% client-side: No upload to servers. Images processed in browser with Canvas API.
Mobile support: Touch-friendly interface for resizing on phones and tablets.
Common use cases
Web image optimization: Reduce image file size for faster website loading. Resize to 1920×1080 or smaller.
Thumbnail generation: Create small preview images (200×200, 400×400) for galleries or product grids.
Social media sizing: Resize to platform requirements (Instagram 1080×1080, Facebook 1200×630, Twitter 1200×675).
Email attachments: Downscale large photos to fit email size limits (10MB → 1MB).
Print preparation: Resize to print dimensions at 300 DPI (8×10 inches = 2400×3000 pixels).
Responsive image sets: Generate multiple sizes for responsive web design (original, 1x, 2x, thumbnail).
Limited by browser memory. Typically supports images up to 50MB or 20,000×20,000 pixels.
Aspect ratio lock
Maintains original width:height ratio. If original is 16:9, resized image is also 16:9. Prevents distortion.
Free resize
Unlocked aspect ratio allows any width×height. May distort image (stretch/squash) if proportions do not match original.
Upscaling vs. downscaling
Downscaling (large → small) is lossless (no quality loss beyond compression). Upscaling (small → large) interpolates pixels and may appear blurry or pixelated.
Quality preservation
PNG output is lossless (exact pixels). JPG re-encodes with quality setting (90% ≈ minimal loss). WebP is typically smaller than JPG for same quality.
Resampling algorithm
Uses bilinear or bicubic interpolation (browser default). Produces smooth results for most images.
Browser compatibility
Works in all modern browsers (Chrome, Firefox, Safari, Edge) with Canvas API support.
Comparison to desktop tools
Simpler than Photoshop/GIMP (no layers, filters). Faster than online tools (no upload). Perfect for quick resizes.
Common mistakes to avoid
Upscaling small images to large sizes, resulting in blurry or pixelated results
Why it happens: Image resizing can only reduce quality, not add detail. If you resize a 500×500 image to 2000×2000, the browser interpolates (guesses) pixels to fill the gaps. The result looks blurry, soft, or pixelated because no new detail is created. You cannot 'enhance' an image like in movies — upscaling does not add resolution.
How to avoid it: Only downscale images (large → small). For large prints or high-res displays, start with a high-resolution source (camera RAW, vector graphics, or original high-res image). If you must upscale, use AI upscaling tools (waifu2x, Topaz Gigapixel) that are designed for this — not simple resizers.
Resizing images without locking aspect ratio, causing distortion
Why it happens: If you resize an image from 1920×1080 (16:9) to 1000×1000 (1:1) with aspect ratio unlocked, the image stretches vertically or horizontally to fit the new dimensions. Faces appear wide, circles become ovals, text is unreadable. This is common when trying to fit images to specific platform sizes without cropping first.
How to avoid it: Always lock aspect ratio unless you intentionally want distortion. If the target aspect ratio differs from the original (16:9 → 1:1), crop the image first to the target ratio (use image cropper), then resize. Or use letterboxing/pillarboxing (add borders) to preserve aspect ratio.
Resizing images multiple times, compounding quality loss each time
Why it happens: If you resize a JPG from 2000×1500 → 1000×750, save it, then resize again to 500×375, and save again, quality degrades with each save (JPG is lossy). After 3-4 resizes, the image has noticeable compression artifacts (blocky patterns, color banding).
How to avoid it: Always resize from the original source image, not from a previously resized version. Keep the original file. If you need multiple sizes (original, thumbnail, mobile), resize each from the original, not sequentially. Or use PNG output (lossless) for intermediate sizes, convert to JPG only for final output.
Using PNG for resized photos, resulting in huge file sizes
Why it happens: PNG is lossless and produces large files for photos (often 5-10× larger than JPG). A resized 1920×1080 photo might be 200KB as JPG but 2MB as PNG. For web use, large files slow down page load times. PNG's benefits (lossless, transparency) are unnecessary for photos without transparency.
How to avoid it: Use JPG for photos without transparency (portraits, landscapes, products). Use PNG only if the image has transparency (alpha channel) or is a graphic/logo where lossless quality is critical. Set JPG quality to 80-90% for a good balance.
Not considering high-DPI displays (Retina) when resizing for web
Why it happens: High-DPI displays (Retina, 4K monitors) render at 2× or 3× pixel density. If you resize an image to 500×500 pixels and display it at 500×500 CSS pixels, it appears blurry on Retina (needs 1000×1000 actual pixels). This is common for hero images, product photos, or icons.
How to avoid it: For high-DPI displays, resize images to 2× or 3× the intended display size. If the image displays at 500×500 CSS pixels, resize to 1000×1000 (2×) or 1500×1500 (3×). Use CSS or HTML width/height to scale it down. This ensures crisp rendering on Retina screens.
Frequently asked questions
What is the difference between resizing and cropping?
Resizing changes the pixel dimensions (width × height) by scaling the entire image. Cropping extracts a portion of the image and discards the rest. Resize to make an image smaller/larger. Crop to remove unwanted areas or change aspect ratio.
Should I use PNG or JPG for resized images?
Use JPG for photos without transparency (smaller file size, faster web loading). Use PNG for images with transparency, logos, graphics, or screenshots with text (lossless, keeps text sharp). For web photos, JPG at 80-90% quality is best.
Can I upscale small images without losing quality?
No. Upscaling adds no new detail — it interpolates (guesses) pixels. Results are blurry or pixelated. For quality upscaling, use AI tools (waifu2x, Topaz Gigapixel) or start with a higher-resolution source image.
What is aspect ratio and why should I lock it?
Aspect ratio is the width-to-height proportion (e.g., 16:9, 4:3). Locking it maintains the original proportions, preventing distortion. If unlocked, the image may stretch or squash to fit new dimensions. Always lock unless you intentionally want distortion.
How do I resize for Retina displays?
Retina displays (2× pixel density) need higher-resolution images. If displaying at 500×500 CSS pixels, resize to 1000×1000 (2×) actual pixels. Use CSS or HTML to scale down. This ensures crisp rendering on high-DPI screens.
What is the best JPG quality setting for web use?
80-90% is a good balance between file size and quality. 90% is nearly indistinguishable from original. 80% reduces file size significantly with minimal visible loss. Below 70%, compression artifacts (blockiness) become noticeable.
Can I resize animated GIFs or videos?
This tool resizes static images only. For animated GIFs, the first frame is resized, but animation is lost. Use a GIF resizer (ezgif.com, GIMP). For videos, use video editing software (FFmpeg, Adobe Premiere, iMovie).