Batch resize, convert, and shrink without quality loss.
Add images, set a target width or file size, and pick an output format. Each file is re-encoded locally, so originals are never modified and nothing leaves your machine.
Drop in JPEG, PNG or WebP files. They are decoded in the tab and never uploaded. Batch as many as you like; each is processed independently.
The height follows automatically to preserve the aspect ratio, so nothing is stretched. Two thousand pixels on the long edge is generous for screen use; twelve hundred is plenty for a website; six hundred is right for an email signature or a thumbnail.
Quality applies to lossy formats and trades file size against artefacts. Around eighty is the usual sweet spot for photographs. Format converts between JPEG, PNG and WebP.
Each file reports the size saved. Originals on disk are never modified — the tool produces new files and leaves your source images alone.
JPEG works by converting the image into frequency components and discarding the high-frequency detail your eye is least sensitive to. At quality ninety the discarded detail is invisible. At fifty it shows as blocking around sharp edges and mottling in smooth gradients like skies. The compression is applied to eight-by-eight pixel blocks, which is why the artefacts are square. Because information is genuinely thrown away, saving a JPEG repeatedly degrades it each time — always re-encode from the original, never from a previously compressed copy.
PNG is lossless: the pixels you put in are the pixels you get out. It compresses by finding patterns, which works brilliantly on flat colour and sharply defined edges and badly on photographic noise. A screenshot, a logo, a diagram or anything with transparency should be PNG. A photograph as PNG is typically three to five times larger than the same image as a good-quality JPEG with no visible benefit.
WebP does both: lossy compression that is roughly a quarter smaller than JPEG at the same visible quality, and a lossless mode that beats PNG. Every current browser supports it. The reasons not to use it are older software and some desktop applications and printers that still do not read it. For a website, WebP is the right default. For a file you are emailing to someone whose software you do not know, JPEG remains the safe choice.
Shrinking an image is not a matter of throwing away every other pixel. Doing that — nearest-neighbour sampling — produces jagged edges and destroys fine detail, because a single surviving pixel has to stand in for the several it replaced without knowing anything about them. Proper downscaling averages each output pixel from the block of input pixels it covers, so detail is condensed rather than discarded, and the result stays smooth. The browser canvas used here applies smoothed resampling by default, which is why a photograph reduced to a third of its size still looks sharp rather than aliased. The visible consequence is that downscaled images often benefit from a touch of sharpening afterwards, since averaging softens edges slightly — something worth doing in an editor if the image is going to be printed.
Pixel dimensions are what matter for screens; the DPI number stored in a file is a print instruction and has no effect on how an image displays. A photograph shown across a typical laptop screen needs about sixteen hundred pixels wide, doubled for a high-density display. A phone-width image needs about eight hundred. Anything beyond that is downloaded and thrown away by the browser, which is the single most common cause of slow pages.
Either it was scaled up, which cannot add detail, or the target width is smaller than the size it is being displayed at. Match the target to the largest size the image will actually appear.
Quality set too low for that image. Smooth gradients are the hardest case for JPEG. Raise quality to eighty-five or higher, or use WebP which handles gradients better at the same size.
JPEG has no transparency and fills it with white. Keep transparent images as PNG or WebP.
Usually converting a photograph to PNG, or raising quality above the original. Re-encoding a JPEG at quality ninety-five when it was saved at eighty adds size without recovering anything.
The source had an embedded colour profile that is not carried through re-encoding. For most photographs the shift is imperceptible; for colour-critical work, resize in software that manages profiles.
Browsers cannot decode HEIC. Set the phone to Most Compatible in the camera settings so it saves JPEG, or export the photograph as JPEG first.
Professional editors give you control over resampling algorithms, colour management, sharpening after resize, and export presets you can save. For work where output quality is the product, use them. For getting a folder of photographs under two megabytes, they are enormous overkill.
Preview on macOS and Photos on Windows both resize adequately and are already installed. Neither handles a batch as conveniently, and neither converts to WebP.
Image compression sites are the most numerous category of free web tool, and many are genuinely good. All of them require uploading your photographs. For holiday snaps that hardly matters; for photographs of people, documents, or anything commercially sensitive, doing it locally is the better habit.
ImageMagick and its relatives will batch-process thousands of files with precise control, and if you are doing this regularly they are the correct answer. They need installing and learning.
JPEG, PNG, and WebP in both directions. WebP usually gives the smallest file at the same visible quality.
Scaling down is effectively lossless to the eye. Scaling up cannot add detail that was not captured, so it will look softer.
Orientation is applied and the rest of the metadata, including location, is stripped by default.