How this tool works
The image is drawn onto a canvas and re-encoded in the format you choose. Because it is a re-encode rather than a rename, the result is a genuine file of that type — which is the difference between converting an image and changing its extension, and the latter produces a file that many programs will refuse to open.
Before anything is written, the browser is asked whether it can actually encode the chosen format, and told plainly if it cannot rather than being allowed to fall back silently. That check matters for AVIF in particular, which Chrome and Edge can produce and Firefox and Safari cannot: without it the canvas quietly returns a PNG and hands you a PNG named with an AVIF extension. Formats without transparency are flattened onto white first, so a transparent background does not come back black.
Choosing a format
- JPEG for photographs, PNG for graphics: JPEG discards detail the eye is poor at noticing, which suits continuous tone and ruins flat colour with sharp edges. PNG keeps everything and supports transparency.
- WebP is the safe modern choice: smaller than both at comparable quality, with transparency, and supported by every current browser. AVIF is smaller again but cannot be created in every browser.
- Converting to a lossless format does not restore quality: a JPEG turned into a PNG keeps every artefact the JPEG already had, in a much larger file. The detail is gone and cannot come back.
- Quality below about eighty starts to show: the setting affects lossy formats only. Around eighty to ninety is where most photographs sit; far below that the artefacts become visible in flat areas.