WebP vs PNG for Comics: Which Format Gives the Best Quality-to-Size Ratio?

You open your comic folder and notice something odd: two scanned chapters of the same series, both looking identical on screen, but one is 45 MB and the other is 14 MB. The difference? One was saved as PNG, the other as WebP. If you've ever wondered why comic archives vary so wildly in size — and whether you're wasting storage on your iPhone — this breakdown will answer it.

Why Image Format Matters for Comics

Comics are image-heavy by nature. A single 24-page issue scanned at print quality can contain anywhere from 50 to 200 images, each several megabytes in PNG form. Scale that to a library of 500 volumes and you're looking at hundreds of gigabytes of storage — most of which comes down to how those images are encoded.

For comic readers, image format choice affects three things: file size (storage and transfer speed), render quality (especially for fine linework and colour gradients), and app compatibility (whether your reader can even open the file). PNG has been the default for scanned comics for decades. WebP is the newer contender, and the results aren't as simple as "newer = better."

How PNG Compression Works

PNG uses lossless compression. Every pixel in the original image is preserved exactly — no data is thrown away. The compression algorithm (DEFLATE) finds patterns in the image data and encodes them more efficiently, but when you decode a PNG, you get back a bit-perfect copy of the original.

For comics, this matters because line art has sharp transitions between black and white. Lossy formats (like standard JPEG) introduce artifacts at those edges — blurry outlines, colour fringing, noise in flat colour fills. PNG avoids all of that. The trade-off is file size: a 3000×4500 px colour scan can easily hit 8–15 MB per page as a PNG.

How WebP Compression Works

WebP was developed by Google and supports both lossless and lossy modes. In lossless mode, WebP typically beats PNG by 25–35% in file size for photographic content. For synthetic images like line art, the gap narrows — sometimes PNG is actually smaller.

In lossy mode, WebP can compress a comic scan to a fraction of PNG size while preserving subjective quality. At quality 85–90, a page that was 12 MB as a lossless PNG might drop to under 1 MB as a lossy WebP — with differences that are nearly invisible at normal reading distances on a phone screen.

The catch: lossy WebP, like JPEG, is permanently destructive. Every re-encode degrades the image slightly. And unlike JPEG, which has been supported everywhere for 30 years, WebP compatibility is still catching up — most comic readers handle it fine in 2026, but a few older tools do not.

Direct Comparison: Same Comic, Different Formats

Here's what a typical colour manga page looks like across formats (approximate values for a 2200×3200 px page):

Format	Mode	File Size	Quality
PNG	Lossless	8.2 MB	Perfect
WebP	Lossless	6.1 MB	Perfect
WebP	Quality 90	1.8 MB	Excellent
WebP	Quality 75	0.9 MB	Good
JPEG	Quality 90	2.1 MB	Excellent
JPEG	Quality 75	1.1 MB	Fair (artifacts)

For scanned black-and-white manga, WebP lossless is typically 20–30% smaller than PNG. For colour art with gradients, WebP lossy at quality 85–90 delivers the best ratio.

How BiblioFuse Handles WebP Comics

BiblioFuse natively supports WebP images inside CBZ archives on both iOS and macOS. When you open a CBZ that contains WebP pages, BiblioFuse decodes them with full hardware acceleration — no slowdown, no visual quality loss from the reader side.

The BiblioFuse web tools also let you compress CBZ archives in your browser. When you run a compress operation, the tool converts PNG pages to WebP at a quality setting tuned to preserve visual fidelity while cutting file size significantly — usually 60–80% reduction for colour scans, 30–50% for black-and-white.

All processing happens entirely in your browser using WebAssembly. Your comics never leave your device — no upload, no account, no server.

Step-by-Step: Convert Your Comic Archive to WebP

1. Go to the BiblioFuse web tool on any browser.
2. Drop a CBZ or ZIP archive onto the Compress area.
3. Adjust the quality slider — start at 85 for colour, 80 for black-and-white.
4. Click Compress. The tool processes everything locally in your browser.
5. Download the result. Open it in BiblioFuse (or any reader) to compare.

If you're unsatisfied with quality, try a higher setting. The tool is non-destructive — your original file is unchanged.

When to Stick With PNG

Lossless PNG still wins in a few scenarios:

Raw scans you plan to edit. If you're a scanlator or archivist who will run processing passes (descreen, denoise, level-adjust), always work in PNG. Running those operations on WebP lossy introduces compounded artifacts.

Line art at small file sizes. For very clean black-and-white linework, PNG's pattern-based compression can match or beat WebP lossless, especially on pages with large solid areas.

Maximum archival safety. If you want a format that will definitely be readable in 20 years with any tool, PNG is the safer bet. WebP is nearly universal now but PNG has 30 years of ubiquity behind it.

When WebP Wins

Large colour libraries. If you have thousands of colour volumes, WebP lossy at quality 85–90 cuts storage by 70–80% with no visible quality difference at typical screen resolutions. On a 128 GB iPhone, that difference is hundreds of gigabytes.

Slow transfers. Sending 50 volumes over Wi-Fi from your Mac to your iPhone? Smaller files mean faster sync. The BiblioFuse home library streaming feature benefits directly from smaller page sizes.

eReader screens. A 326 ppi iPhone display or 250 ppi iPad display cannot resolve the difference between PNG and WebP quality 90. The extra data from PNG is literally imperceptible.

Frequently Asked Questions

Does lossy compression affect reading experience? At quality 85+, no. The artifacts are below the threshold of perception at normal reading distance. Quality below 75 can show banding in gradients and softening of fine lines.

Can BiblioFuse open CBZ files containing mixed WebP and PNG pages? Yes. BiblioFuse detects each page's format independently. Mixed-format archives work correctly.

What about AVIF? Is it better than WebP? AVIF is newer still and offers even better compression ratios, particularly for photos. For comics in 2026, AVIF encoder/decoder support in reading apps is still inconsistent. WebP is the better practical choice for now.

The Practical Verdict

For an active reading library on your iPhone, WebP at quality 85–90 is the right call for colour comics — dramatically smaller, visually identical at screen resolutions. For black-and-white manga, the gains are smaller but still real. Keep a PNG master copy of anything precious; use WebP for everything you actually read.

BiblioFuse handles both seamlessly, and the web tool makes conversion a 30-second job with no software to install.