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Image Resizer & Thumbnail Generator

Processed Client Side

Resize images to any size and turn them into thumbnails — pick an exact width and height, a ready-made preset like YouTube 1280×720 or Open Graph 1200×630, a maximum dimension, or a percentage. Crop or letterbox to fit, convert the format while you are at it, and cap the file size. Everything runs in your browser, so your images are never uploaded.

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About Image Resizer

This tool runs entirely in your browser. Whatever you paste is processed on your own device and is never uploaded, logged, or sent to any server.

The Image Resizer turns a full-size photo or screenshot into whatever dimensions you actually need — an exact width and height, a ready-made preset like a 1280×720 YouTube thumbnail or a 1200×630 Open Graph image, a maximum longest side, or a plain percentage of the original. You decide how a mismatched aspect ratio is handled: crop to fill, letterbox to fit, or stretch. Because thumbnails usually need to be light as well as small, you can change the output format on the way through and cap the result at a file size like 50 KB. Decoding, resizing, and re-encoding all happen in your browser, so nothing is uploaded.

Key features

  • Four ways to size an image: exact width × height, a named preset, a maximum dimension, or a percentage
  • Fifteen presets covering website thumbnails and cards, YouTube, Open Graph, Facebook, Twitter/X, LinkedIn, Instagram (square, portrait, story), Pinterest, avatars, app icons, and favicons
  • Cover, contain, and stretch fit modes, with a transparent, white, black, or custom background behind letterboxed images
  • Reads PNG, JPG, WebP, AVIF, GIF, BMP, ICO, SVG, and iPhone HEIC/HEIF; writes PNG, JPG, WebP, or "same as input"
  • Maximum file size mode that searches for the highest quality still fitting your KB budget
  • Large live preview plus original → resized dimensions, file size, and the percentage saved
  • Batch resizing with per-file stats, a batch total, and Download all
  • Filename styles: photo-1280x720, photo-thumbnail, photo-resized, or unchanged
  • 100% client-side — your images never leave your device

How to use it

  1. Choose how you want to size the image: a preset, an exact width and height, a maximum dimension, or a percentage.
  2. Pick the fit — Cover crops to fill the box, Contain fits the whole image inside it, Stretch distorts to the exact size.
  3. Set the output format (or leave it on "Same as input"), then either drag the quality slider or switch on a maximum file size.
  4. Drop in one or more images, or click to browse.
  5. Check the preview and the size stats, then save each file or use Download all.

Tips & common mistakes

  • Cover is the right default for thumbnails: every output is exactly the size you asked for, with the overflow cropped from the centre. Use Contain when nothing may be cut off — a logo or a product shot — and accept the bars.
  • Resizing cannot add detail that was never captured, which is why "Don't enlarge images smaller than the target" is on by default. Turn it off only when you genuinely need the larger canvas.
  • Maximum file size only works for JPG and WebP. PNG is lossless and has no quality dial, so a PNG that is too heavy usually needs smaller dimensions or a switch to WebP instead.
  • WebP is the best all-round thumbnail format — typically 25–35% smaller than JPG at the same visual quality, and it keeps transparency.
  • Downscaling below half size is done in repeated halving steps rather than one jump, which is what keeps small thumbnails sharp instead of speckled.
  • Animated GIFs are resized as a single still frame — the first one.

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Frequently asked questions

8

Choose "Exact size", type the width and height in pixels, and drop your image in. Turn off "Lock ratio" if you want to set the two values independently. Every output is exactly the size you asked for — the Fit setting decides what happens to any part of the image that does not match that shape.

No. Decoding, resizing, and re-encoding all run in your browser using the canvas API, so your images never leave your device. The tool also keeps working offline once the page has loaded.

Cover scales the image until it fills the whole box and crops the overflow from the centre — nothing is distorted and nothing is left blank, which is what you normally want for a thumbnail. Contain scales it until the entire image fits inside the box, leaving bars in your chosen background colour. Stretch squashes the image to the exact box, which changes its proportions.

Yes. Switch on "Compress to size" and enter your budget in KB. The tool encodes the image repeatedly, searching for the highest quality that still fits under the limit. It works for JPG and WebP; PNG is lossless and has no quality setting to trade away. If even the lowest quality is too big, you get the smallest file it could produce and a note saying so — reduce the dimensions and try again.

It depends on where it goes: 1280×720 for a YouTube thumbnail, 1200×630 for an Open Graph or Facebook link preview, 1200×627 for LinkedIn, 1080×1080 for an Instagram square, 1080×1920 for a story, and 300×200 or 400×300 for a typical website card. All of these are one-click presets, so you do not have to remember them.

Making an image smaller discards pixels, but done properly it still looks sharp — this tool downscales in repeated halving steps, which avoids the speckled look a single large jump produces. Quality loss mostly comes from re-encoding to a lossy format, so keep the quality slider high, or use PNG or WebP, when it matters.

You can, but it will not gain detail — enlarging only interpolates the pixels that are already there, so the result looks soft. That is why "Don't enlarge images smaller than the target" is on by default. While it is on, the output is capped at the source resolution, so a small image sent to a 1280×720 preset comes out proportionally smaller rather than blurry — switch the toggle off when you need the exact preset size regardless. SVG files are the exception: they are vectors, so they always rasterize crisply at any size.

Yes. Drop in as many files as you like — each is resized with the same settings and listed separately with its own before-and-after stats, plus a total for the batch. Download all saves the whole set.