Resize Images in Your Browser
Drop an image above to open the resize controls. Set your target dimensions in pixels or scale by percentage. Supports all common formats including PNG, JPEG, WebP, and more. Aspect ratio is maintained by default, so your images stay proportional. Pick an output format and download the result. Nothing leaves your machine.
How Image Resizing Works
Resizing a raster image means changing its pixel grid from one set of dimensions to another. This is a non-trivial operation because the source and target grids rarely align pixel-for-pixel. The algorithm must decide what color each pixel in the new grid should be, a process called resampling.
Interpolation methods
When the target dimensions do not map cleanly onto the source, the resizer must interpolate between existing pixel values.
Nearest-neighbor picks the closest source pixel. Fast but jagged. Only useful for pixel art at exact integer multiples.
Bilinear interpolation averages the four nearest source pixels, weighted by distance. Smoother than nearest-neighbor but can soften fine details.
Bicubic interpolation considers the 16 nearest source pixels (a 4x4 grid) and fits a cubic function through them. This is what most image editors and this tool use. It preserves sharpness better than bilinear and handles gradients cleanly. The Canvas API’s imageSmoothingQuality: "high" setting enables this.
Downscaling vs. upscaling
Downscaling is the forgiving direction. You are removing pixel data, and interpolation blends neighboring pixels smoothly. A 4000x3000 photo downscaled to 1200x900 will look sharp because there is more source data than the target needs.
Upscaling works in reverse: the algorithm must fabricate pixel data that was never captured. A 200x200 thumbnail stretched to 800x800 will look soft regardless of the interpolation method. Bicubic handles this better than bilinear, but stay under 150-200% if you need the result to look clean.
Aspect Ratio
Aspect ratio is the proportional relationship between width and height. A 1920x1080 image has a 16:9 ratio. Changing one dimension without adjusting the other distorts the image: faces stretch, circles become ovals, text warps.
This tool locks aspect ratio by default. Enter a width and the height calculates automatically. Unlock it only when you intentionally want to change the proportions, which is rare outside of specific design requirements.
When resizing for a platform with fixed dimensions (Instagram square at 1080x1080, Twitter header at 1500x500), you may need to crop or pad the image. Resizing alone cannot change a 4:3 photo into 1:1 without distortion or content loss.
Common Use Cases
Thumbnails and previews
Most web applications need images at multiple sizes: a 1200px hero image, a 400px card thumbnail, and a 100px cart icon, all from one source file. Serving the appropriately sized version avoids forcing the browser to download and downscale a large file on every page load.
Social media dimensions
Each platform has preferred image sizes: Open Graph previews at 1200x630, Twitter cards at 1200x675, LinkedIn posts at 1200x627. Uploading an image at the correct dimensions prevents the platform from cropping unpredictably or adding black bars.
Email optimization
Email HTML has no responsive image support in most clients. Images render at their native pixel dimensions or at the container width, whichever is smaller. Resizing to exactly 600px wide (the standard full-width email content) keeps file sizes low and rendering predictable.
Retina and high-DPI displays
Retina screens display at 2x or 3x density. An image displayed at 400px CSS width needs to be 800px or 1200px in actual pixels to look crisp. Resize your source to 2x the display dimensions, then set explicit width/height attributes in HTML.
Pixel Dimensions vs. Percentage Scaling
Pixel dimensions are absolute. Set 1200x800 and the output is exactly that, regardless of the input size. Use this when you know the exact dimensions you need, like platform-specific sizes or layout constraints.
Percentage scaling is relative. Setting 50% on any input halves both dimensions. This is practical when batch-resizing images of different sizes and you want them all reduced by the same factor, such as generating smaller versions of a photo gallery.
Tips for Choosing Dimensions
Use dimensions that are multiples of 8 or 16 when targeting JPEG or WebP output, since both formats compress in 8x8 blocks. Non-multiples of 8 still work, but the encoder pads the edge blocks.
For web use, 2560px is a practical maximum width. It covers 2x resolution on a 1280px viewport (standard laptop). Resizing a 6000px camera photo down to 2560px cuts file size dramatically while preserving enough detail for any screen.
For file format guidance after resizing, the Image Converter handles conversion between PNG, JPG, WebP, and more. To embed resized images directly in code or stylesheets, the Base64 Encoder converts any image to a data URI.