The transparency problem nobody warns you about
Convert a logo from PNG to JPG on most free converters and you get a black rectangle where the transparent background used to be. That is not a bug in the file — JPEG simply has no alpha channel, so the transparent pixels have to become something, and a converter that does not ask you picks whatever its canvas defaulted to.
This tool asks. When the target format cannot store transparency, you choose the fill colour: white for documents and most upload forms, black for dark interfaces, or any custom colour to match the background it will sit on. If you would rather keep the transparency, convert to PNG, WebP or AVIF instead — all three support an alpha channel.
Which format to pick
| Format | Transparency | Relative size | Best for |
|---|---|---|---|
| JPG | No | Baseline | Photos going to forms, email, older systems |
| PNG | Yes | Much larger for photos | Logos, icons, screenshots, anything needing exact pixels |
| WebP | Yes | ~25–35% below JPG | Websites you control; the safe modern default |
| AVIF | Yes | ~30–50% below JPG | Maximum compression when compatibility is not a concern |
The short version: JPG when someone else built the destination, WebP when you did. AVIF wins on file size but encodes noticeably more slowly and is still rejected by plenty of upload forms. PNG is the wrong choice for photographs — being lossless, it can produce files several times larger than JPG for no visible benefit — but the right choice for anything with sharp edges, flat colour or transparency.
Browser support is checked before you convert
Not every browser can write every format, even when it can display it. This matters because the underlying browser API fails quietly: ask it for AVIF on a browser that cannot encode AVIF and it hands back a PNG with an AVIF-looking file name. You would only find out when the destination rejected the file.
This tool tests each format when the page loads and disables the ones your browser cannot produce. If a conversion somehow still comes back in the wrong format, it is reported as a failure rather than offered as a download.
Lossy, lossless, and why the original matters
PNG is lossless: converting to PNG never discards image data. JPG, WebP and AVIF are lossy at the quality settings offered here, which means each conversion throws away a little detail to save space.
The practical consequence is that repeated conversions accumulate damage. Taking a JPEG, converting it to WebP, then back to JPEG, then to AVIF leaves you with something visibly worse than any single conversion from the original would have produced. Whenever you can, convert from the source file rather than from a copy that has already been through the mill.
The quality setting applies only to the lossy formats. 85% is a sensible default: the difference from 95% is hard to see on a photograph and the file is substantially smaller. It is ignored entirely when the target is PNG.
Converting a batch
Drop in any mix of formats — a folder containing PNGs, JPEGs and WebP files
all at once is fine — and every one of them is converted to the single target
you picked, then returned as one ZIP. File names keep their base and get the new
extension, so logo.png becomes logo.webp.
Because the conversion runs on your own device there is no upload step, no file count limit and no queue. It also means metadata is stripped as a side effect: re-encoding through a canvas discards EXIF, so GPS coordinates and camera details do not survive the conversion. Keep your originals if you need that information later.