Image Resizer
Resize images by exact pixels or percentage. Lock aspect ratio to avoid distortion. 100% browser-based — your images stay private.
Drop image here or click to upload
JPG, PNG, WebP — max 20 MB
How to Use
Frequently Asked Questions
What is aspect ratio lock?▼
It auto-adjusts height when you change width, keeping the image proportional.
What output formats are available?▼
Choose between JPEG, PNG, or WebP output.
What is the maximum size?▼
Up to 10,000 × 10,000 pixels.
Everything About Image Resizing
Optimize web display with correct resolution and size settings. SNS, print, and web recommended sizes fully explained.
Image Size and Web Display Basics
Image "size" has two meanings: pixel dimensions (width × height) and file size (bytes). Both matter for web performance. High-pixel images take longer to display, and are wasteful when shown in small areas on the page.
Responsive Image Size Guide
- Hero image: 1920×1080px (Full HD) or 2560×1440px (2K)
- OGP/Social share: 1200×630px (Facebook/Twitter standard)
- Blog thumbnail: 1280×720px (16:9) or 1200×900px (4:3)
- E-commerce product: Minimum 800×800px. For zoom support: 2000×2000px
- Avatar/Profile: 400×400px or more (square)
Recommended Sizes by Platform
1600×900px(16:9)1080×1080px(1:1)1080×1920px(9:16)1200×630px(1.91:1)1200×627px(1.91:1)1280×720px(16:9)Image Resizing Best Practices
When resizing images, choosing the right resampling algorithm for the use case matters as much as the resize itself. Lanczos is commonly used for downscaling; bicubic interpolation for upscaling.
Maintaining Aspect Ratio
Resizing while maintaining aspect ratio prevents distortion. For example, resizing 1920×1080px (16:9) to 960px width automatically gives 540px height. Sometimes intentional cropping is needed for specific aspect ratios.
Retina Display Support
Apple MacBook and iPhone Retina displays have 2-3× pixel density. For sharp web display, provide images at 2× size and display them at half size with CSS. The srcset attribute can automatically serve the right image size per device.
Downscale only (upscaling degrades)
Cannot exceed original pixels. Use SVG for unlimited scalability
Lock aspect ratio when resizing
Many tools fix ratio when holding Shift while dragging
Provide 2x images for Retina
srcset="img.jpg 1x, img@2x.jpg 2x" for auto-switching
300DPI+ required for print
A4 print requires minimum 2480×3508px