Image Converter

Which format should you actually pick?

For photographs going onto a website, WebP is the default worth reaching for. It is roughly a quarter to a third smaller than JPEG at the same visual quality, supports transparency, and works in every browser released since 2020. The only reason to avoid it is a destination that rejects it.

For anything that has to be accepted by an unknown system — an upload form, a printer, an older content management system, a government portal — JPG remains the safe floor. It has been universally supported since 1992 and nothing refuses it.

For screenshots, logos, diagrams, and anything with hard edges, flat colour or transparency, PNG is correct. Lossy compression is designed for the smooth gradients of photographs; applied to a screenshot full of small text it produces visible halos around every letter.

AVIF is smaller still than WebP, but browsers can currently decode it without being able to encode it through the canvas API, so this tool reads AVIF and does not yet write it.

Understanding the quality slider

The slider only applies to lossy formats — JPG and WebP. PNG is lossless, so there is no size-versus-fidelity dial to turn, which is why the control greys out when you select it.

Quality is not a percentage of anything meaningful; it is a knob on the encoder's aggressiveness. As a rough guide: 95 and above is visually indistinguishable from the source and produces large files; 85 to 92 is the sweet spot for most photographic work; 75 to 85 is fine for web images viewed at normal size; below 70, artefacts become obvious on skin tones, skies and gradients.

Content matters more than the number. A photograph of foliage hides compression noise beautifully. A flat blue corporate background shows banding at settings where a landscape looks perfect. If a specific image matters, convert it twice at different settings and compare.

Transparency, and where it goes

PNG, WebP, AVIF and GIF all support an alpha channel. JPG does not, and never will — the format has no way to represent it.

When you convert a transparent image to JPG, every transparent pixel has to be given a colour. This tool composites onto white, which is the sensible default and matches what most people expect. It is also irreversible: once flattened, the transparency cannot be recovered from the JPG.

That is worth remembering when converting a logo. A cut-out logo saved as JPG will have a white rectangle around it, which looks wrong on any coloured background. Convert logos to PNG or WebP instead.

Everything runs on your device

Conversion uses the browser's own image pipeline: the file is decoded into an off-screen canvas and re-encoded in the target format. That is the same code path used to render every image on every web page you visit, so it is fast and thoroughly tested.

Because it is local, there is no upload, no queue, and no file size cap beyond your available memory. Speed depends on your hardware rather than on server load, and a batch of fifty images is processed one at a time so that memory use stays flat rather than growing with the batch.

The practical way to verify the claim: load this page, disconnect from the network, and convert something. It keeps working, because there was never anything to send.