Image Resize & Compress
Resize images by width or height and optionally compress them in one browser-based tool.
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Source image
Target size
Width (px): Height (px):
Leave width or height empty to keep aspect ratio based on the other.
Format: Quality: 0.8
Preview
About Image Resizer
This image resizer lets you change image dimensions directly in your browser without uploading files to a server. It is useful for thumbnails, avatars, blog images, product images and quick content publishing tasks.
You can resize by width or height while keeping the original aspect ratio, preview the result and download the new image in one step.
How Image Resizing Works
This tool uses HTML5 Canvas for client-side image processing:
- Load: Original image is loaded into memory via FileReader API
- Scale: Canvas is resized to target dimensions
- Render: Image is drawn onto canvas at new size using browser's built-in interpolation
- Export: Canvas is exported to selected format (PNG/JPEG/WebP) with quality setting
Image Format Comparison
| Format | Compression | Transparency | Best For |
|---|---|---|---|
| PNG | Lossless | Yes (alpha channel) | Logos, screenshots, graphics |
| JPEG | Lossy | No | Photos, complex images |
| WebP | Lossy/Lossless | Yes | Modern web (best compression) |
Recommended Image Sizes
| Use Case | Recommended Size | Format |
|---|---|---|
| Avatar | 200x200 to 400x400 px | JPEG/WebP |
| Thumbnail | 200-400 px wide | JPEG/WebP |
| Blog featured | 800-1200 px wide | JPEG/WebP |
| Product image | 800-1500 px wide | JPEG/WebP |
| Full-width hero | 1920 px wide | JPEG/WebP |
| Social OG image | 1200x630 px | JPEG |
| Logo | Original dimensions | PNG |
Understanding Quality Settings
Quality controls the compression level for JPEG and WebP formats:
- 1.0 (Maximum): Minimal compression, largest file size
- 0.8-0.9 (High): Good quality, reasonable file size (recommended)
- 0.6-0.7 (Medium): Noticeable compression, smaller files
- 0.4-0.5 (Low): Visible artifacts, much smaller files
- 0.1-0.3 (Minimum): Heavy artifacts, smallest files
Why Resize Images for Web?
- Faster page loads: Smaller images download quicker, especially on mobile
- Better Core Web Vitals: Image size directly impacts LCP (Largest Contentful Paint)
- Reduced bandwidth: Lower hosting costs and CDN expenses
- Improved SEO: Page speed is a Google ranking factor
- Better UX: Users don't wait for slow-loading images
Aspect Ratio Explained
Aspect ratio is the proportional relationship between width and height:
- 1:1 (Square): 400x400, 800x800 - Avatars, Instagram posts
- 4:3: 800x600, 1024x768 - Traditional photos
- 16:9: 1920x1080, 1280x720 - Widescreen, YouTube thumbnails
- 3:2: 600x400, 900x600 - DSLR photos
When you enter only one dimension (width OR height), this tool automatically calculates the other to preserve aspect ratio.
How to Resize Images
- Upload image: Click the file input to select an image from your device.
- Set dimensions: Enter target width or height (leave one empty for automatic aspect ratio).
- Choose format: Select PNG (lossless), JPEG (photos), or WebP (modern web).
- Adjust quality: Set compression level (0.8 recommended for web use).
- Process and preview: Click "Process Image" to resize and see the result.
- Download: Click the download link to save the resized image.
Tips for Best Results
- Resize to your layout's maximum display width - no larger
- Use WebP for best compression with modern browsers
- Keep quality at 0.8 for good balance of size and quality
- For transparent images, use PNG or WebP (not JPEG)
- Consider creating multiple sizes for responsive images
Frequently Asked Questions
- How does image resizing work?
- Image resizing changes the pixel dimensions of an image. When downscaling, the browser combines multiple pixels into one using interpolation algorithms. When upscaling, new pixels are created by estimating values between existing ones. This tool uses canvas-based resizing with bilinear interpolation.
- What is the difference between PNG, JPEG, and WebP?
- PNG uses lossless compression (preserves all detail, larger files, supports transparency). JPEG uses lossy compression (smaller files, some quality loss, no transparency). WebP is a modern format offering both lossy and lossless compression with better compression than JPEG/PNG at similar quality.
- What does image quality setting do?
- Quality (0.1 to 1.0) controls compression level for JPEG and WebP formats. Lower quality = smaller file size but more compression artifacts. Quality 0.8 is a good balance for web use. PNG is lossless so quality setting has no effect on PNG output.
- Why should I resize images for web?
- Large images slow down page loads, increase bandwidth costs, and hurt Core Web Vitals scores. Resizing images to their display dimensions reduces file size dramatically. For example, a 4000px photo displayed at 400px wastes 90%+ of its data. Optimized images improve SEO and user experience.
- What size should I use for common use cases?
- Common sizes: Avatar (150-400px square), Thumbnail (200-400px wide), Blog featured image (800-1200px wide), Full-width hero (1920px wide), Product images (800-1500px wide), Social media OG images (1200x630px). Always consider your layout's maximum display width.
- Does this tool preserve aspect ratio?
- Yes. If you only enter width OR height (leave the other empty), the tool automatically calculates the missing dimension to maintain the original aspect ratio. If you enter both, the image will be stretched to fit those exact dimensions.