PNG vs WebP: File Size, Quality & Transparency Compared

Laura Cummins

Jan 18, 2026 5 min read

Updated Jan 18, 2026

PNG has been the default format for transparent graphics on the web since the late 1990s. WebP, released by Google in 2010, compresses those same images 26-40% smaller without discarding a single pixel. The tradeoff is straightforward: WebP gives you smaller files, PNG gives you wider compatibility and deeper color.

PNG and WebP Side by Side

PNG uses DEFLATE compression, the same algorithm behind ZIP files. It was designed in 1996 as a patent-free replacement for GIF, and it remains the only lossless format with truly universal browser support. WebP applies VP8-based predictive coding that analyzes spatial patterns in the image data, achieving tighter compression on the same lossless content.

The difference matters most for graphics-heavy pages. A logo, icon set, or UI screenshot stored as an 800KB PNG becomes a 480KB WebP lossless file -- 320KB saved per image with no visual difference. Across a site serving hundreds of assets, that compounds into meaningful bandwidth reduction.

File Size: WebP Lossless Saves 26-40%

Google's own benchmarks put WebP lossless at 26% smaller than PNG across a diverse image corpus. In practice, the savings vary by content type. Flat-color graphics like logos and UI elements often compress 35-40% smaller. Photographic content converted from lossless PNG sees closer to 26% reduction.

For an 800KB PNG logo with transparency, WebP lossless produces a 480KB file. That 320KB difference matters when the same logo appears on every page of a site. At 100,000 monthly page views, you save 30GB of bandwidth on a single asset.

Lossy WebP pushes the savings further. A PNG with transparency that weighs 800KB can become a 260KB lossy WebP with alpha -- roughly 3x smaller. The lossy version introduces minor compression artifacts, but for web-sized thumbnails and icons, the difference is imperceptible at quality 80+.

Transparency: Both Formats, Different Efficiency

PNG and WebP both support full alpha channel transparency with 256 levels of opacity per pixel. The visual result is identical. The difference is size.

Adding transparency to a PNG increases file size substantially because the alpha channel is stored as an additional uncompressed data stream alongside the RGB data. WebP handles transparency more efficiently. Lossy WebP with an alpha channel costs only 22% additional bytes compared to the same image without transparency. PNG's overhead is far larger.

This makes WebP the clear choice for transparent web assets. Logos on dark backgrounds, product images with removed backgrounds, UI overlays -- all of these benefit from WebP's compact transparency handling.

Color Depth and Resolution Limits

PNG supports 16-bit color depth: 65,536 discrete shades per channel, totaling over 281 trillion possible colors. WebP is limited to 8-bit: 256 shades per channel, roughly 16.7 million colors. For standard web content viewed on consumer displays (which are 8-bit panels), the difference is invisible. For print production, medical imaging, or scientific visualization, PNG's extra color depth preserves data that WebP cannot store.

PNG also has no practical dimension limit -- the specification allows images up to 2^31 pixels per side. WebP caps at 16,383 x 16,383 pixels. Most web images fall well within WebP's limit, but panoramic photography, satellite imagery, and large-format print files may exceed it.

How to Convert PNG to WebP Without Quality Loss

The conversion workflow is straightforward and produces identical visual output:

1. Audit your PNG usage. Review your website assets and identify PNGs that could benefit from WebP conversion. Focus on large files first: logos, UI screenshots, and icons with transparency.
2. Compress your PNG files. Upload PNGs to LighterImage to strip unnecessary metadata and apply maximum DEFLATE compression. This gives you the smallest possible PNG as a starting point.
3. Convert to WebP lossless. Use a tool like Sharp, cwebp -lossless, or Squoosh to convert. The lossless flag ensures pixel-identical output.
4. Serve WebP with PNG fallback. Use the <picture> element so the 97% of browsers supporting WebP get the smaller file, while the remaining 3% receive the PNG.

<picture>
  <source srcset="logo.webp" type="image/webp">
  <img src="logo.png" alt="Description" loading="lazy">
</picture>

CDNs like Cloudflare and AWS CloudFront can automate this format negotiation using the Accept header, so you upload one PNG and the CDN serves WebP to supported browsers automatically.

PNG or WebP: A Decision Framework

Use PNG when...

• You need 16-bit color depth for print-quality or scientific images
• Your image exceeds 16,383 pixels on any side
• Universal 100% browser support is non-negotiable (email templates, legacy systems)
• You are archiving source files for future editing

Use WebP when...

• You are serving images on a website and want 26-40% smaller files at identical quality
• Your images have transparency and file size matters (logos, icons, product cutouts)
• You need animation support as a modern format option
• Your CDN or build pipeline supports automatic WebP conversion

See how WebP stacks up against JPG in our WebP vs JPG comparison, or explore all format comparisons.