Image Compressor

about this tool

The browser's own encoders

There is no codec library to download. Each file is decoded — with its EXIF orientation applied, so phone photos come out the right way up — drawn onto a canvas at the chosen size and re-encoded by the browser's built-in JPEG, WebP or AVIF encoder at the quality you set, or by the lossless PNG encoder. The tool asks the browser which lossy encoders it has and greys out the ones it lacks; WebP is the default because every current browser writes it and it beats JPEG by a quarter to a third at the same quality while keeping transparency.

Files are processed one after another so a batch of forty holiday photos does not lock the page, and every option change re-runs the whole batch. Each row shows the original and new dimensions and sizes with the saving, a thumbnail, and a note when the encoder choice cost something — transparent areas becoming white in JPEG, a fallback when AVIF was asked for and the browser cannot write it.

Honesty about PNG and already-small files

PNG is lossless, so the browser's encoder cannot make a PNG smaller by discarding detail, and a file that has already been through an optimiser is frequently as small as PNG gets. A result larger than its original is not offered: the row says the original was kept, and the download and the zip contain the original. The way to shrink a PNG is to resize it, or to convert it to WebP with the format control, which keeps its transparency.

Resizing

The longest-side control fits the image within 2560, 1920, 1280 or 800 px, never upscaling, keeping the aspect ratio to the nearest pixel. This is where most of the saving usually is: a 4000 px photo shown at 800 px carries twenty-five times the pixels it needs.

Metadata

Re-encoding through a canvas drops everything but the pixels: EXIF, the camera model, timestamps, GPS location and colour profiles (the image is converted to sRGB on the way). That is a privacy feature when publishing photos and a limitation when you need the metadata kept.

Limits

HEIC and other formats the browser cannot decode are refused with a message; SVGs are pointed at the SVG optimiser. Animated GIFs lose their animation — the first frame is what a canvas sees. Encoding quality is whatever the browser's encoder does; a dedicated tool such as mozjpeg or oxipng will typically shave a further five to fifteen percent. Very large images are limited by the canvas size the browser allows, around 16 000 px a side. Nothing is stored.

To change format as well as size — WebP or AVIF usually beat JPEG at the same quality — use the image format converter. To change the pixel dimensions, image resize & crop.

questions

How does compressing in the browser work?

The image is decoded onto a canvas and re-encoded by the browser’s own JPEG, WebP or AVIF encoder at the quality you set, optionally at a smaller size. Nothing is uploaded and there is no server; the encoders are the same ones the browser uses to save images itself.

Why did a PNG get bigger, or not shrink?

PNG is lossless: the browser’s encoder cannot throw detail away, and a file already run through an optimiser is often as small as PNG gets. The tool keeps the original when a result comes out larger. To make a PNG smaller, resize it, or convert it to WebP, which keeps transparency at a fraction of the size.

What quality should I use?

0.8 is the usual web setting and looks identical to the original at normal viewing sizes. 0.9 and above is for images people will inspect closely; 0.65 is fine for thumbnails. The biggest saving is usually not quality but size: a 4000-pixel phone photo shown 800 pixels wide can lose 90% of its bytes by being resized first.

Does compressing remove EXIF data?

Yes, all of it: camera details, timestamps and GPS location do not survive re-encoding through a canvas. The image is first rotated the way the EXIF orientation tag says, so photos come out the right way up without the tag. If you need the metadata kept, this is not the tool.

Why is AVIF greyed out?

Because your browser cannot write AVIF. Chrome and Firefox can; Safari, at the time of writing, can only read it. WebP is written by every current browser and is the default here; JPEG and PNG always work.