Convert between PNG, JPEG and WebP

Your files and your privacy

Your images are never uploaded. Each file is read into this browser tab, decoded and re-encoded by the browser’s own image pipeline inside a Web Worker, and handed back as a download. The page’s Content-Security-Policy restricts connect-src to this origin, so the browser itself would block an upload even if the code attempted one.

What this tool does

Convert an image from one format to another using the encoders your browser already ships with. PNG, JPEG and WebP can be written; JPEG, PNG, WebP and GIF can be read. Before anything is written, the panel states whether the conversion is lossy and what will happen to transparency.

Converting decodes your picture into plain RGBA pixels and asks a different encoder to write them out again, which means a conversion carries only what the destination format can represent. PNG is written by a lossless encoder and keeps an alpha channel. JPEG is lossy at every setting and has no alpha at all, so transparent pixels are flattened onto a background colour you pick before encoding. WebP keeps alpha but is written in lossy mode by the browser, even at quality 100. The panel names each of those consequences for the exact conversion you asked for.

How to use it

1. Choose the image, or several images, that you want to convert.
2. Pick the output format. The note under the picker describes what that encoder does with detail and with transparency.
3. If you chose JPEG, set the background colour that transparent areas will be flattened onto. It starts at white.
4. Select Convert and read the warning panel, which lists every consequence of this particular conversion.
5. Download the converted file, or a ZIP when you converted more than one.

Example use cases

• Turning a PNG screenshot into a JPEG so it fits inside a size-limited upload form.
• Producing a WebP copy of a logo that keeps its transparent background but weighs less than the PNG.
• Saving the first frame of a GIF as a still PNG for use in a document.

Supported input and output

Accepts

• JPEG, PNG and WebP, up to 40 MB per file
• GIF, decoded as its first frame only

Produces

• PNG: lossless encoder, keeps transparency, large for photographs
• JPEG: always lossy, no alpha channel, small for photographs
• WebP: lossy in the browser encoder, keeps transparency
• A ZIP named converted-images.zip for a batch

What this tool will not do

• GIF is input only. Animation is not preserved, and GIF is not offered as an output format, because a still image with a .gif extension would misrepresent itself.
• HEIC, HEIF, AVIF, TIFF and camera RAW are not accepted, because browsers cannot decode them reliably without a platform codec.
• Converting a JPEG to PNG recovers nothing. The PNG faithfully stores the pixels the JPEG already degraded, usually in a considerably larger file.
• WebP output needs a browser that can encode WebP. One that cannot reports an error rather than quietly writing a different format.
• Metadata is generally lost as a side effect of re-encoding, which is not the same thing as a guarantee that it was removed.
• Colour profiles are not carried through the canvas, so an image with an unusual embedded profile can shift slightly in colour.

Common mistakes

• Exporting a transparent PNG as JPEG and only noticing later that the transparency became a solid block of the background colour, which defaults to white.
• Expecting PNG output to shrink a photograph. Its encoder stores every pixel exactly, so the result is routinely several times the size of the JPEG it came from.
• Reading WebP at quality 100 as lossless. The browser encodes WebP in lossy mode at every setting, so detail is discarded even at the top of the slider.
• Converting an animated GIF and shipping the result as an animation: only the first frame is decoded, so the output is a single still image.

Technical notes

Decoding uses createImageBitmap, which handles every input type the browser can read and behaves identically inside a Web Worker. The bitmap is drawn once into an OffscreenCanvas and encoded by the browser through convertToBlob, with canvas.toBlob as the fallback. Because a canvas holds nothing but RGBA pixels, anything a source format carried beyond pixels survives only if the destination encoder can represent it: for a format without an alpha channel the canvas is filled with your chosen matte colour before the bitmap is drawn, which is why transparency becomes a flat colour rather than black in one browser and white in another.

Frequently asked questions

Which conversions are lossless?

Only writing to PNG, and only when you do not also change the pixel dimensions. Every JPEG export is lossy, WebP is lossy in the browser encoder at any quality, and any resize resamples the image regardless of format.

What happens to transparency when I convert to JPEG?

JPEG has no alpha channel, so every transparent pixel is filled with the background colour you choose before encoding. If you need to keep transparency, convert to PNG or WebP instead.

Can I convert HEIC photos from an iPhone?

No. HEIC and HEIF are not accepted, and neither are AVIF, TIFF or camera RAW, because a browser cannot decode them without help from the operating system. Export a JPEG from your phone first.