What resampling algorithm does the image resizer use?

The resizer uses Lanczos3 resampling for downscaling — the same algorithm used by Photoshop's 'Bicubic Sharper' mode — which produces the sharpest, cleanest results with minimal aliasing. For upscaling, bilinear interpolation is used, which produces smooth results without the ringing artifacts of Lanczos upscaling. Both algorithms run in WebAssembly for native performance speed.

Can I resize images while keeping the aspect ratio?

Yes — enabling the 'lock aspect ratio' option ensures that when you change width or height, the other dimension is automatically calculated to maintain the original proportions. This prevents stretching or squishing distortion. Disable aspect ratio lock only when you intentionally need non-proportional resizing, such as fitting an image to a fixed-dimension slot in a layout.

Are my images uploaded to a server when I resize them?

No. The image resizer uses the HTML5 Canvas API and WebAssembly pixel processing entirely within your browser. Full-resolution photos, which may contain EXIF metadata including GPS location and timestamp, are resized locally and never transmitted to any server. The resized output file is generated in browser memory and downloaded directly to your device.

What is the maximum image size I can resize?

The practical limit is determined by your device's available browser memory rather than a hard restriction. Most modern computers can resize images up to 50–100 megapixels (e.g., a 10,000×10,000 pixel image) without issues. Very large images — such as those from high-resolution scanners or gigapixel cameras — may require more memory than lower-end devices provide; if the browser becomes unresponsive, resize the image in smaller steps.

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FreeNo Upload

Image Resizer

Resize images to any dimension instantly. Supports all major image formats.

syncConvert animationVideo→GIF compressCompress auto_fix_highRemove BG photo_size_select_largeResize cropCrop rotate_rightRotate auto_fix_highFilter water_dropWatermark brushDraw burst_modeBatch

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Drop your image here

Set custom dimensions

JPG, PNG, WebP · Max 50MB

Quick Presets — Pick a size, then upload your image

Short Video & Portrait

Landscape Covers

Square & Other Platforms

ID Photos (300 dpi)

How to Use

upload_file

Upload your image

Select an image to resize. Supported formats include JPEG, PNG, WebP, AVIF, and HEIC. Your original stays untouched on your device.

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Set target dimensions

Enter the desired width and height in pixels. Toggle aspect ratio lock to maintain proportions or unlock for custom dimensions. Choose a preset size for common uses.

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Resize and download

Click Resize to generate the downsized (or upsized) image. Download the result — perfect for web optimization, social media, or email attachments.

What is Image Resizer?

The image resizer changes the pixel dimensions of JPG, PNG, WebP, and other raster images, allowing you to scale images up or down by exact pixel values or by percentage — with an option to lock the aspect ratio to prevent distortion. Image resizing is a fundamental operation required for preparing assets for social media platforms, app stores, email campaigns, and web layouts that specify exact image dimensions. All resizing is performed in the browser using high-quality Lanczos resampling for sharp, alias-free output.

Why use Image Resizer?

Uploading correctly sized images instead of relying on the browser or CMS to scale them down reduces bandwidth consumption, improves rendering performance, and prevents layout shifts caused by improperly sized placeholders. Browser-based image resizing requires no software installation and produces results equivalent to Photoshop's Image Size dialog, using the same bicubic-equivalent algorithms for smooth downscaling. Client-side processing keeps confidential documents, personal photos, and proprietary product images entirely private.

lockComplete privacy — Your files never leave your device or browser.
boltInstant processing — No wait times, no server queues, no upload delays.
money_off100% free — No subscriptions, no credits, no hidden fees.
person_offNo registration — Start using immediately, no account needed.
devicesWorks everywhere — Any modern browser on desktop, tablet, or mobile.

How it works

Social media managers resize images to platform-specific dimensions — 1200×630 for Facebook, 1080×1080 for Instagram, 1500×500 for Twitter headers — before scheduling posts to avoid automatic cropping by the platform. App developers prepare icon assets at multiple resolutions by resizing a master image to 512, 256, 128, 64, and 32 pixels in sequence. Bloggers resize large camera photos from 6000×4000 pixels down to 1200×800 before uploading to their CMS to save storage and reduce page load time.

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Pro Tip

Always scale down from the highest-resolution source available — downscaling is almost always higher quality than upscaling, which can produce blurry or pixelated results. When resizing for retina displays, output at 2× your intended CSS pixel size (e.g., 400×400 for a 200×200 display slot) and let CSS scale it down for sharp rendering on high-DPI screens.

Frequently Asked Questions

Downscaling (making an image smaller) generally maintains or improves perceived sharpness because the resampling algorithm averages pixel data to create a denser image. Upscaling (making an image larger) always reduces quality — the algorithm must interpolate pixel data that does not exist, resulting in blurriness or pixelation. Use a high-quality source image at the largest needed size and scale down, never up, for best results.

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