Almost every image headed for the web needs two things done to it: a format change and a size reduction. A four-megabyte phone photo uploaded as-is makes the page crawl, and a logo that needs transparency turns black the moment you save it as JPG.
This tool does both on a browser canvas. It reads PNG, JPG, WebP, GIF, AVIF and SVG, writes PNG, JPEG or WebP, resizes by width, height or percentage, and trims file size with a quality slider. Nothing is uploaded, so scanned contracts and internal material are safe to work with.
How to use
- Add an image — Click the dashed area to choose a file or drag one in. The original dimensions and file size appear immediately. The image is decoded in browser memory and never sent anywhere.
- Choose an output format — WebP is the most efficient if the goal is a smaller file. Use PNG or WebP when you need transparency, and JPEG when it is a photograph and maximum compatibility matters. Choosing JPEG reveals a background colour picker for filling transparent areas.
- Resize — Resize by width, by height, to fit a box, or by percentage. Body images on the web rarely need more than 1200px wide, and thumbnails are fine around 400px. Fit in box scales down to fit inside your dimensions while preserving aspect ratio, and never scales up.
- Set quality and download — Moving the quality slider recomputes the file size live. Watch the preview on the right for visible degradation as you go, then download. The filename keeps the original name with the new extension.
Frequently asked questions
What quality setting should I use?
For photographs, somewhere between 75% and 85%. That range cuts file size substantially with degradation most people will not notice. Above 90% the file grows without a visible payoff.
It depends on the image, though. Wide gradients and screenshots containing text show banding and fringing much earlier, so those often need 90% or more. Dragging the slider while watching the preview zoomed in is the only reliable way to decide.
I converted a PNG to JPG and the background turned black.
JPEG has no alpha channel, so transparent pixels have to be filled with something — and with nothing specified, that something is usually black.
Selecting JPEG here reveals a background picker that defaults to white. Set it to match your page background and it will look natural. If you genuinely need transparency, use PNG or WebP instead; WebP supports alpha at a fraction of PNG's size.
My converted file is bigger than the original.
A few situations cause that. Converting an already-compressed JPEG to PNG inflates it considerably, because PNG is lossless — PNG is simply the wrong format for photographs.
The reverse also happens: a simple graphic or logo saved as JPEG can grow. JPEG is tuned for images where colour varies smoothly, and handles flat areas with hard edges inefficiently. Photographs want JPEG or WebP; logos and icons want PNG or WebP.
Can I convert several images at once?
One at a time, currently. Everything runs in browser memory, and loading several large images simultaneously can hang or crash the tab, so intake is deliberately limited to a single file.
For a batch of dozens, a CLI tool fits better — ImageMagick (magick mogrify -resize 1200x -quality 82 *.jpg) or sharp. This tool is built for tuning a handful of images while looking at them.
Concepts worth knowing
Lossless versus lossy
PNG is lossless, so the original pixels survive exactly. Save and reopen it any number of times and nothing changes. JPEG and lossy WebP instead discard detail the eye is unlikely to notice in order to shrink the file.
The crucial difference is that loss accumulates. Opening a JPEG, editing it and saving again throws away a little more each round, and the image degrades steadily. Keep working files in PNG or their original format and convert to JPEG once, at the end, right before publishing.
How much smaller WebP actually is
At equivalent quality, roughly 25–35% smaller than JPEG, and dramatically smaller than PNG. It supports transparency while still offering lossy compression, so it covers both PNG's alpha channel and JPEG's compression ratio.
Compatibility is largely a solved problem: every major browser supports it, including Safari since version 14. What remains is everything that is not a browser — some email clients, older image editors and certain messaging app previews still handle WebP poorly. Choose based on where the image is going.
Prepare images at twice the display size
Retina displays paint one CSS pixel with two or more physical pixels, so an image displayed at 600px looks soft if you export it at 600px.
The usual answer is to export at double the display size. Doubling both dimensions quadruples the pixel count, though, so pair it with a slightly lower quality setting. The eye tolerates compression artefacts better than it tolerates insufficient resolution, which makes a large image at lower quality generally preferable to a small one at high quality.