Compress an image without uploading it

Need an icon rather than a smaller photo? The favicon generator cuts one image into favicon.ico and every PNG size browsers ask for — in your browser too.

Getting a smaller file without a worse image

Two things determine the size of an image file, and only one of them is the quality slider:

• Dimensions matter more than quality. Halving the width and height quarters the pixel count. A 4000px photo displayed in a 800px column is carrying sixteen times more data than it can show. Resizing first is almost always the bigger win.
• Quality has a floor of diminishing returns. Between 100 and about 80 you lose file size and almost no visible detail. Below roughly 60 the artefacts become obvious, especially around text and sharp edges. 80 is a good default.

For a photograph on a web page, 1920px wide at quality 80 in WebP is a reasonable target and will usually land somewhere between 100 and 300 KB — often a tenth of what came off the camera.

AVIF and JPEG XL: the two smaller formats

AVIF, built from the AV1 video codec, typically produces a photograph around half the size of a JPEG and noticeably smaller than WebP at the same visible quality. Every current browser displays it and Google indexes it for image search, so it is safe to publish on its own. The trade is encoding time: it searches hard for the smallest file, so a large photo takes a second or two here rather than being instant.

JPEG XL matches AVIF on ordinary photographs and does better at high quality, carries transparency, and loads progressively. Its weakness is reach: Safari has displayed it since 2023 and Chrome has only recently followed, and Google's list of indexable image formats does not include it. Publish it as the first source in a <picture> element with an AVIF or JPEG fallback, never alone.

The quality slider means the same thing for every format here. AVIF's encoder counts on a different scale from JPEG's, so the page translates — 80 on the slider asks AVIF for the fidelity JPEG gives at 80, rather than AVIF's own 80, which is far finer and would make files no smaller than WebP's. The resizer covers what the two formats mean for search in more detail.

Common questions

Is my image uploaded anywhere?

No, and this is the main reason to use this page rather than most alternatives. The image is decoded, resized, and re-encoded by your own browser — with the canvas API for JPEG, PNG, and WebP, and with WebAssembly encoders running on your device for AVIF and JPEG XL. It is never sent to a server, which means it cannot be stored, scanned, or leaked, and the page keeps working with no network connection once the encoders you use have loaded.

Which format should I choose?

For the smallest photograph that every current browser can show, AVIF — typically around half the size of a JPEG and noticeably smaller than WebP at the same visible quality, at the cost of a second or two to encode. WebP is the instant, safe choice, roughly 25 to 35 percent smaller than JPEG. JPEG XL compresses as well as AVIF and better at high quality, but not every browser displays it yet, so publish it only alongside a fallback. Keep PNG for flat-colour graphics such as logos and screenshots of text, and use JPEG only when something downstream cannot read anything newer.

Why did my file get bigger?

Usually because it was already well optimised, or because it is a flat graphic being re-encoded as a photograph format. Re-encoding always loses a little and occasionally costs more than it saves. The comparison is shown before you download, so you can see it happen and keep the original instead.

Does compressing twice halve the size again?

No, and it will visibly degrade the image. Lossy compression discards detail permanently, so a second pass throws away information from an already-reduced version rather than from the original. Always compress from the original file.

Why does AVIF or JPEG XL take a moment to compress?

Because no browser can write either format itself, so this page brings its own encoders — the open-source Squoosh codecs, compiled to WebAssembly and run in a background thread on your device. AVIF in particular searches hard for the smallest file at a given quality, which is where its savings come from and why a large photo takes a second or two. The encoder downloads the first time you pick the format, not before.

Why can I not use a HEIC photo from my iPhone?

Browsers cannot decode HEIC, so there is nothing this page could do with it. On an iPhone you can change Settings, Camera, Formats to Most Compatible to capture JPEG instead, or share the photo in a way that converts it — sending it to yourself in most apps produces a JPEG.