Local processing · no image upload

Bulk PNG to WebP converter

Convert static PNG assets to WebP inside your browser and keep transparent pixels in the WebP output.

BatchMint converts static PNG pixels to WebP locally and preserves the alpha channel. The result can be much smaller for some transparent assets, but lossless PNG can remain preferable for exact flat-color graphics or workflows that do not accept WebP.

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Use cases

Convert transparent product cutouts for modern storefronts
Reduce transfer size for decorative website assets
Standardize a group of static PNG files as WebP

Transparency is preserved, but edge quality still matters

WebP supports alpha transparency, so transparent pixels do not need a matte background. However, semi-transparent antialiased edges can reveal halos when displayed over a background that differs from the one used during design.

Review logos, hair, glass and soft shadows over both light and dark backgrounds before publishing.

PNG and WebP solve different problems

PNG is lossless and broadly supported by design software. The current BatchMint WebP output uses lossy quality settings with alpha, which can be effective for product cutouts but can alter tiny color details.

Keep PNG for pixel-exact UI captures, line art or archival masters.
Try WebP for detailed transparent storefront imagery.
Keep the original PNG because conversion is not a reversible archive operation.

A measured transparent-fixture result

In BatchMint's deterministic 1200×1200 transparent fixture, the unoptimized PNG was 1,541,671 bytes; OxiPNG level 2 produced 67,465 bytes and WebP quality 82 with alpha produced 80,516 bytes. This unusually compressible fixture shows why content matters and why WebP is not automatically the smallest result.

How local browser processing works

The selected PNG is decoded by the browser, transferred to a local worker as pixels, optionally resized or watermarked and encoded with the bundled libwebp-based jSquash codec. The result is returned as a browser-local Blob; the original PNG and transparent pixels are not sent to BatchMint servers.

Selected images, filenames and watermark text are not sent to a BatchMint processing server. The browser still requests the site code, styles and codec assets used on demand.

Read the complete privacy model

How to use it

Choose static PNG files and select WebP output.
Set optional maximum width, target size and watermark settings.
Process locally and review transparency against the intended background.

Sources and verification dates

Platform rules can change. Marketplace requirements below link to official pages, with the retrieval date and scope recorded for each source.

BatchMint transparent-image benchmark
Includes downloadable PNG and WebP files and exact byte counts.
JPEG, PNG, WebP and AVIF comparison
Transparency, compatibility, suitable uses and limitations.

Limitations

Animated PNG is not supported.
The current WebP path is lossy rather than a WebP-lossless control.
Publishing systems and older desktop tools can have uneven WebP support.

FAQ

Is PNG transparency preserved?

Yes. WebP supports alpha transparency and BatchMint keeps transparent pixels in the output.

Will WebP always be smaller than PNG?

No. It often helps with detailed imagery, but optimized PNG can be smaller for simple flat-color or highly compressible graphics.

Evidence and privacy

Selected image bytes, filenames and watermark text are not sent to BatchMint servers.

Read the testing methodology