Resize JPG, PNG, and WebP images to an exact width and height, right in your browser. Lock the aspect ratio, or jump straight to a social media or video preset like HD, 4K, or Twitter.
Drag and drop an image here, or click below to browse. JPG, PNG, and WebP supported.
Every image on a web page costs bytes to download and pixels to decode, and shipping an image far larger than it will ever be displayed is one of the most common, easily avoidable sources of page bloat — a 4000-pixel-wide photo squeezed into an 800-pixel-wide thumbnail slot forces every visitor's browser to download and decode four to five times more pixel data than will ever actually be shown. Resizing an image to the dimensions it will genuinely be displayed at, before uploading it to a website, CMS, or app, is one of the simplest and highest-leverage image performance optimizations available.
Beyond web performance, resizing matters constantly outside of code too: fitting a photo into a specific social media platform's recommended dimensions so it isn't awkwardly cropped or padded, preparing a thumbnail at an exact pixel size a video platform requires, or simply making a photo small enough to attach to an email or message with a size limit. Having exact, precise control over target width and height — rather than a vague 'small/medium/large' setting — matters whenever a destination has a specific pixel requirement.
This tool works by decoding your uploaded image and drawing it onto an in-memory HTML canvas element sized to your target width and height — the browser's own image-drawing routine handles the actual pixel resampling as part of that draw operation, using the same high-quality image scaling algorithms your browser already relies on whenever it renders any image at a size different from its native resolution. Once drawn, the canvas is re-exported as a new image file at the requested format, entirely through standard, well-supported browser APIs (Canvas and the File/Blob APIs) with no server round-trip or third-party service involved.
Setting imageSmoothingQuality to 'high' (which this tool does by default) instructs the browser to use its best available resampling algorithm rather than a faster, lower-quality one, trading a small amount of processing time for a cleaner result — this matters most when scaling up, where resampling quality has the biggest visible impact on the final image's sharpness and lack of visible aliasing artifacts.
Aspect ratio is simply the proportional relationship between an image's width and height, commonly expressed as a ratio like 16:9 (widescreen video) or 1:1 (square). Preserving aspect ratio when resizing means the resized image is a uniformly scaled version of the original — every part of the image shrinks or grows by the same factor in both directions, so nothing looks stretched, squashed, or distorted. Breaking aspect ratio (setting a width and height combination that doesn't match the original proportions) instead stretches the image non-uniformly, which is occasionally exactly what you want (forcing a photo into a fixed banner slot, for example) but usually produces a visibly distorted result for anything with recognizable shapes, like faces or straight architectural lines.
This is precisely why the Lock aspect ratio toggle exists as the default-on behavior in this tool: for the overwhelming majority of resizing tasks — shrinking a photo for a thumbnail, preparing an image for a specific max-width constraint — you want the proportional, non-distorting version, and having the height field auto-calculate as you type a width (or vice versa) removes the need to do that arithmetic yourself or accidentally introduce visible distortion.
For web page content images, resize to the largest size the image will actually be displayed at across your site's responsive breakpoints — oversizing 'just in case' defeats the purpose, while undersizing means the image will look soft or pixelated when a wider layout tries to display it larger than its native resolution. For social media, matching the platform's specific recommended dimensions (which is exactly what the built-in presets target) avoids the platform's own automatic cropping or letterboxing behavior, which can otherwise unpredictably cut off part of your image or add unwanted padding.
For video thumbnails and video-adjacent graphics, the HD and Full HD presets match the two most common video resolution standards, ensuring your thumbnail's aspect ratio lines up cleanly with the video player it will sit next to. When in doubt about an exact target size, err toward resizing to a modestly larger size than you think you need rather than smaller — a slightly oversized image can always be displayed a bit smaller with no quality loss, while an undersized image can't be enlarged back to full sharpness once it's been shrunk.
Image Resizer changes an image's pixel dimensions. These related image tools cover other common parts of an image-preparation workflow.