Tinker Tools

Image Resizer Instantly

Resize images to any dimension with ease. All processing is done locally in your browser—your images never leave your device.

Preview

Drop your image here or click to browse

Supports PNG, JPEG, WebP, GIF, BMP

How it works

1. Upload Image

Drag and drop or click to upload any image file. We support all common image formats including PNG, JPEG, WebP, GIF, and BMP.

Local Processing

2. Set Dimensions

Enter your desired width and height. Lock aspect ratio to maintain proportions, or unlock for custom dimensions. Choose your preferred output format.

Aspect Ratio Lock

3. Download Result

Preview the resized image side-by-side with the original and download your result in PNG, JPEG, or WebP format with one click.

High Quality

Frequently Asked Questions

What is Image Resizing?

Image resizing changes the pixel dimensions of a picture — its width and height — without altering the underlying file format. A 4000x3000 photo from your phone contains twelve million pixels. Display it in a 400x300 thumbnail on a product page and the browser still has to download all twelve million pixels, decode them, and then scale them down on the fly. That wastes bandwidth, slows rendering, and drains battery on mobile devices. Resizing ahead of time gives you an image that matches its display context exactly, so every pixel in the file earns its keep.

Pixel dimensions and DPI are two different things, and confusing them causes trouble. Pixel dimensions describe the actual grid of color data — 1920 pixels wide by 1080 pixels tall, for example. DPI — dots per inch — only matters when the image is printed on paper. A 300 DPI setting tells a printer to pack 300 pixels into every physical inch. On screen, DPI is irrelevant because monitors have fixed pixel grids. A 1920x1080 image displays identically whether its metadata says 72 DPI or 300 DPI. When you resize for the web, focus entirely on pixel dimensions. When you resize for print, multiply the desired physical size in inches by the target DPI to get the pixel dimensions you need. A 4x6 inch print at 300 DPI requires 1200x1800 pixels.

This tool resizes your images entirely inside your browser using the Canvas API drawImage() method. You pick a target width or height, the tool calculates the other dimension to preserve the aspect ratio, and then it redraws the image onto a canvas of the new size. Nothing gets uploaded to any server. Your files stay on your machine from start to finish, which matters when you are working with client photos, proprietary mockups, or anything else you would rather not send across the internet.

Key Features and Benefits

  • Aspect ratio locking — When you change the width, the height adjusts automatically to maintain the original proportions — and vice versa. This prevents the stretched or squashed look that ruins photos. If you do need a non-proportional resize — say, converting a 16:9 banner into a 1:1 square — you can unlock the ratio and crop or pad as needed.
  • Resampling algorithm selection — Different resampling methods produce different quality levels. Nearest-neighbor simply copies the closest pixel, which works for pixel art but creates jagged edges on photographs. Bilinear interpolation averages the four nearest pixels for a smoother result. Bicubic interpolation considers sixteen surrounding pixels and preserves sharper edges. Lanczos resampling uses a sinc-based windowed kernel — typically Lanczos-3 with a 6x6 pixel neighborhood — and delivers the highest quality for photographic downscaling. This tool lets you choose the method that fits your use case.
  • Preset targets for social media — Social platforms each have their own preferred image dimensions. Instagram feed posts work best at 1080x1080. Facebook shared links want 1200x630. Twitter summary cards expect 800x418. LinkedIn article covers look sharp at 1200x627. YouTube thumbnails need 1280x720. Instead of memorizing all these numbers, pick a platform preset and the tool applies the correct dimensions instantly.
  • Custom dimension input — Type in any width and height you need. Building a blog with a content column that maxes out at 760 pixels? Set 760 as the width. Preparing assets for a retina display? Double your CSS pixel dimensions — a 380px-wide element needs a 760px-wide image at 2x resolution. The input fields accept any positive integer up to 16384 pixels in either direction.
  • Real-time preview — See the resized result before you download. The preview renders at actual pixel size inside a scrollable viewport, so you can check whether text remains readable, edges stay crisp, and small details survive the scaling. If the result looks too soft, try switching from bilinear to Lanczos resampling or reducing the scale factor less aggressively.
  • Batch resizing — Drop multiple files at once and apply the same target dimensions to all of them. This is useful when you are preparing a gallery where every image needs to be exactly 1200 pixels wide, or when you are generating a set of thumbnails at 300x300 for a product catalog. The output arrives as a zip archive with each file named to match the original.

How to Resize Images Online

  1. 1

    Upload your image

    Drag and drop your file onto the upload area or click to open the file picker. The tool accepts JPEG, PNG, WebP, and GIF files up to 50 MB. It reads the file locally using the browser File API and immediately displays the current pixel dimensions so you know your starting point.

  2. 2

    Choose a resize method

    Select a social media preset if your target platform is in the list. Otherwise, type in a custom width or height. With aspect ratio locked — the default — entering one dimension calculates the other. If you need exact control over both dimensions, unlock the ratio and enter both values manually. Keep in mind that stretching a 1:1 image to 16:9 without cropping will distort the subject.

  3. 3

    Pick a resampling algorithm

    For photographs, Lanczos gives the sharpest results at the cost of slightly more processing time. Bicubic is a solid all-around choice and works well for most web images. Bilinear is faster but slightly softer. Nearest-neighbor is only appropriate for pixel art or when you intentionally want a blocky, retro look. The default is Lanczos — change it only if you have a specific reason.

  4. 4

    Preview and adjust

    The preview panel shows the resized output at 100% zoom. Scroll around to inspect fine details. If text or thin lines look blurry, try increasing the target dimensions slightly or switching to a higher-quality resampling method. The goal is an image that looks good at the size it will actually be displayed, not one that looks good zoomed in to 400%.

  5. 5

    Download the resized image

    Click download. The browser generates the new file on the spot using Canvas API toBlob(). The original file stays untouched in your downloads folder or wherever you sourced it. If you uploaded a batch, you get a zip file containing every resized image with its original filename plus a size suffix.

Expert Tips for Image Resizing

Always resize down, not up. Enlarging a small image forces the algorithm to invent pixels that never existed. Even Lanczos resampling cannot add real detail — it can only interpolate a smoother approximation. A 200x200 image upscaled to 800x800 will look noticeably blurry or artificially smooth compared to a native 800x800 capture. If you need a larger version, go back to the original source or use a dedicated AI upscaling tool that generates plausible detail using trained neural networks.

Resize before you compress. This order matters more than most people realize. A 4000x3000 photo compressed to JPEG quality 80 weighs about 1.2 MB. Resize it first to 1200x900 and then compress at the same quality 80, and you end up around 180 KB — an 85% reduction. The compressor has far fewer pixels to encode, so it can represent them more efficiently at the same quality setting. If you compress first and resize second, you are decompressing the JPEG, resampling the already-degraded pixel data, and then re-encoding it — introducing a second generation of compression artifacts.

Understand how the Canvas API drawImage() works under the hood. When you call drawImage(source, 0, 0, newWidth, newHeight), the browser uses its built-in resampling — usually bilinear in most implementations. Chrome and Firefox apply a stepping algorithm for large downscales, resizing in multiple 50% steps rather than jumping straight from 4000px to 400px in one pass. This multi-step approach avoids the aliasing and moire patterns that single-step downsampling can introduce. If you are building your own resizing pipeline, consider replicating this stepped approach or using OffscreenCanvas for better performance on background threads.

Account for device pixel ratios when sizing images for the web. A CSS pixel is not the same as a physical pixel on high-density screens. An iPhone with a 3x display renders a 300px-wide CSS element using 900 physical pixels. If you serve a 300px-wide image, the device stretches it 3x and it looks soft. Serve a 900px-wide image and it appears crisp. The common approach is to generate images at 1x, 2x, and sometimes 3x sizes, then use the HTML srcset attribute to let the browser pick the right one. For most websites, 2x is the practical sweet spot — it covers retina laptops and mid-range phones without the file size penalty of 3x assets.

Related Tools

Image Compressor

Reduce file size after resizing for the smallest possible output

Thumbnail Size Calculator

Find the right thumbnail dimensions for your platform

Social Image Size Guide

Look up the exact pixel requirements for every major social platform

Resizing is the single most effective way to reduce image weight for the web. A properly sized image — one whose pixel dimensions match its display context — eliminates wasted data before compression even begins. Pair resizing with compression and you can turn a 5 MB camera photo into a 120 KB web asset that loads in under a second on a 3G connection. Add a thumbnail calculator and social media size guide into your workflow and you will never have to guess dimensions again. Every step runs in your browser, so your files remain private and your workflow stays fast.

Recommended Tools

Image Compressor

Compress images with adjustable quality. Reduce file size while preserving visual quality.

Color Converter

Convert colors between HEX, RGB, HSL, and HSB formats with a live color preview.

Color Contrast Checker

Check WCAG color contrast ratios between text and background for accessibility compliance.