Compress images online, on your device

The right format depends on what the picture shows and where it will be used. A photo and a logo do not compress the same way.

If you are not sure, leave it on "Original": every image keeps its format, so there are no surprises when someone opens it.

• JPG: the format for photos. It opens everywhere, on every device and in every program. It has no transparency, and it smudges text and flat areas of colour.
• PNG: no quality loss, and transparency is kept. The right pick for a logo, a screenshot or a diagram. For a photo the file stays large.
• WebP: smaller than JPG at a comparable quality, with transparency as well. Every current browser reads it, which makes it a good format for websites.
• AVIF: usually the smallest of the four. Encoding is slower and some older software cannot open it yet. Best kept for the web, ideally with a JPG fallback.

The quality slider runs from 10 to 100. The lower the value, the smaller the file and the more visible the flaws: soft areas, blocks in gradients, fuzzy edges around text.

The three presets cover most needs. When in doubt, start from "Balanced", look at the result with the before and after slider, and go one step lower if you cannot see a difference.

• Small (55): for an image sent in a chat, a thumbnail, or an attachment that has to fit under a size limit.
• Balanced (75): the default. It suits photos on a website, in an online shop or in an article.
• Quality (90): for an image that will be printed, enlarged or edited afterwards. The saving is more modest.
• PNG has no quality setting: the tool optimises it without loss, pixel for pixel.

On many pages, images are the heaviest thing to download. A photo straight from a phone weighs several megabytes, yet it is often displayed in a box a few hundred pixels wide. The visitor downloads far more data than the page needs, and on a mobile network that costs seconds.

Google measures this with a metric called LCP, the time it takes for the largest visible element to appear, which is very often an image. It rates that time as good when it is under 2.5 seconds. Two steps usually get you most of the way there: resize the image to the size it is really displayed at, then compress it.

A lighter image also means less mobile data used by your visitors and less space taken up on your hosting.

Before you touch the quality, reduce the dimensions: that is where most of the saving comes from. A phone photo is often 4000 pixels wide, far more than a screen displays. Turn on "Resize" and enter a maximum width or height. Proportions are kept.

Here are some simple reference points. They are practical rules of thumb, not requirements set by the platforms, which recompress images in their own way in any case.

• WhatsApp and other messaging apps: 1600 pixels on the longest side is plenty for a phone screen. The app recompresses photos sent in a chat by itself.
• Instagram: photos are displayed at up to 1080 pixels wide. Uploading anything larger gains nothing.
• Link preview image (Facebook, LinkedIn, WhatsApp): 1200 × 630 pixels is the most common size.
• Website: 1600 to 1920 pixels wide for a large header image, 800 to 1200 pixels for an image inside text, 400 to 600 pixels for a product thumbnail.
• Email: 1200 pixels wide at most, so the attachment stays light.

Most online compressors upload your photos to their servers, process them there, and send the result back. This one does not: the compression program is downloaded into your browser once, then it runs on your phone or computer, much like an installed app.

In practice your images never leave your device. Nobody but you can see them, and there is nothing to delete from a server afterwards. That matters for client photos, identity documents, or pictures that have not been published yet.

It also means speed depends on your device, not on your connection. A 12-megapixel photo takes a few seconds on a recent computer and longer on an entry-level phone. AVIF needs more computing than the other formats.

The settings you choose are remembered in your browser for next time. Your images are never stored: they are gone when you close the page.