Converting image formats in the browser
A browser ships exactly three image encoders: JPEG, PNG and WebP. For those three, this tool decodes your file, draws it onto a canvas at its native resolution, and asks the browser to re-encode it. For GIF, BMP, TIFF and ICO there is no browser encoder to ask, so this tool writes those formats byte by byte itself. Either way, no server is involved and nothing extra is downloaded.
Because the work happens locally, there is no upload wait and no size cap beyond what your device's memory allows. It also means your images never touch a third party's disk, which matters for anything you would not post publicly.
Choosing a format
JPG is lossy and universally supported. It is still the right choice for photographs destined for software that predates the modern formats, but it cannot store transparency and it degrades every time it is re-saved.
PNG is lossless and supports transparency. It excels at screenshots, diagrams, logos and pixel art — anything with flat color and hard edges. It is a poor fit for photographs, where it often produces files several times larger than JPG.
WebP supports both lossy and lossless modes plus transparency, and typically lands 25–35% smaller than an equivalent JPG. It is the pragmatic default for web delivery today.
GIF, BMP, TIFF and ICO are here for the software that still expects them. GIF is capped at 256 colours, so it suits flat graphics rather than photographs. BMP and TIFF are written uncompressed and will come out considerably larger than the source. ICO cannot store a side longer than 256px, so larger images are scaled down and the tool says so.
AVIF can be read here but not written. No browser exposes an AVIF encoder, so no client-side tool can honestly offer it as an output — producing one needs a multi-megabyte encoder download, which would undercut the point of a tool that loads instantly. Drop an AVIF in and convert it to anything else; you just cannot convert to it.
Quality settings and generation loss
The quality slider maps to the encoder's own quality parameter for the lossy formats. PNG ignores it entirely, because lossless compression has no quality dial — only a speed/size tradeoff the browser handles internally.
Each lossy re-encode discards a little more information, and that loss compounds. Converting JPG to WebP and back to JPG will look worse than either single conversion. Where possible, convert once from the highest-quality original you have rather than chaining conversions.
When to use a converter
- Shrinking page weight by moving site images from JPG or PNG to WebP
- Producing a JPG for a system that rejects newer formats
- Turning a screenshot into PNG so text stays crisp
- Flattening a transparent PNG onto white for a printed document