What is this calculator?
Converts a JPEG, PNG, or WebP image to WebP in your browser. WebP typically produces noticeably smaller files than JPEG or PNG at equivalent visual quality, while still supporting transparency — which is why it has become the default choice for web imagery.
Use it when:
- You are optimising images for a website and want smaller files.
- You need a smaller file that still has an alpha channel, which JPEG cannot provide.
- You are batching assets into a single modern format.
Intended for: Web developers and content authors optimising page weight.
How is this calculated?
- The file you choose is read only for its type and name — nothing is uploaded, and the image itself never leaves your device.
- The tool validates that the source format is supported and that the requested output format and quality are valid together, producing a deterministic conversion plan: output format, quality, output file name, and the transparency and metadata policies that will apply.
- The output file name is derived from the source name with its extension replaced, so the result is predictable rather than randomly named.
- Your browser then decodes the image, draws it to a canvas at its original dimensions, and re-encodes it in the target format using its own built-in encoder.
- Because the image is decoded to raw pixels and re-encoded, the output carries only pixel data — embedded metadata such as EXIF is not preserved.
Example
Converting a 2.4 MB `banner.png` with transparency to WebP at quality 0.92.
- PNG is a supported source and WebP supports alpha, so transparency is preserved.
- The output name becomes `banner.webp`.
Result: `banner.webp` with transparency intact, typically a large size reduction against the PNG — the exact figure depends on the image content.
Frequently asked questions
How much smaller is WebP in practice?
For photographs, commonly 25–35% smaller than JPEG at similar quality. For graphics with flat colour and transparency, often dramatically smaller than PNG. The saving depends entirely on the image.
Is WebP supported everywhere?
By every current major browser. Very old browsers and some desktop applications still do not read it, so keep a JPEG or PNG fallback if you must support them.
What does the quality setting actually do?
It controls how aggressively a lossy encoder discards detail. Values around 0.8 to 0.92 are usually indistinguishable from the original at a fraction of the size; below about 0.7, compression artefacts become visible around edges and in flat areas.
Is my image uploaded anywhere?
No. The image is decoded and re-encoded by your own browser. It is never transmitted to a server, and nothing is stored after you leave the page.
Assumptions
What this calculator takes as given:
- Conversion happens entirely in your browser; the image is never uploaded to or stored on a server.
- Pixel dimensions are preserved exactly — the tool changes the format, not the size.
- The quality setting applies only to lossy encoders (JPEG and WebP); PNG is always lossless.
- Encoding uses your browser's own image encoder, so the exact output bytes can differ slightly between browsers.
Limitations
What this calculator cannot know or does not model:
- Metadata such as EXIF, GPS coordinates, and colour profiles is not carried over — useful for privacy, but a loss if you needed it.
- Resizing, cropping, rotation, and other edits are outside the tool's scope.
- Animated images are converted as a single still frame.
- Very large images may exhaust browser memory, since decoding happens in the page.
- The final file size depends on your browser's encoder and cannot be predicted before encoding.