Convert PNG to WebP

The case for converting a PNG to WebP

A PNG is lossless, which is excellent for the image and poor for the file size. A logo or a screenshot saved as PNG can be several times larger than the same content in WebP, and for a page with a lot of graphics that difference is the whole story. WebP gives both lossless and lossy options with a real alpha channel, so a transparent PNG can usually become a much smaller transparent WebP with no visible change.

NoteWebP lossless is smaller than PNG for most content, but not universally. A simple image with very few colours can be nearly the same size in both.

Lossless or lossy, and the choice that matters for text

This is the decision JPG conversion does not offer, and it is the main reason to convert a PNG rather than keep it. Lossless WebP preserves every pixel, so a diagram or a logo is unchanged, and it is still usually smaller than PNG. Lossy WebP is much smaller again but discards detail, which is fine for a photograph and wrong for text, where it introduces ringing around the glyph edges. For anything with text in it, use lossless.

• Logo, icon, or diagram: use lossless WebP. No visual change, smaller file.
• Screenshot with small text: use lossless. Lossy will fringe the text.
• Photograph: lossy WebP, balanced quality, and a much smaller file.
• Flat colour graphics: lossless avoids banding that a lossy setting would create.

Where PNG is still the better answer

Two situations argue for keeping the PNG. The first is a destination that rejects WebP, such as some email clients, older publishing tools, or a print supplier. The second is a need to edit the file again, because editing a lossy WebP repeatedly compounds the loss and a PNG master does not. Neither is a strong reason to keep PNG as the web format, but both are enough to say that the conversion is not automatically an improvement.

• The destination does not accept WebP. Send the PNG instead.
• You need to edit the image further. Work from a PNG master.
• You need a file for a print supplier. PNG is more likely to be accepted.
• Otherwise, WebP is a good default for the web.

A note on odd dimensions and older bugs

Very small images, exactly 1 pixel wide or tall, and a few other edge cases have historically been handled inconsistently by WebP encoders. Those are corner cases rather than a practical concern for photographs and graphics, but if a conversion produces a visibly broken result on a tiny image, re-exporting it slightly larger usually resolves it. For anything else, the standard path works reliably.

• Normal images convert correctly.
• A 1 pixel wide or tall image is a known edge case in some encoders.
• Re-export slightly larger if a tiny image looks broken.
• This is rare and specific to very small images.