Why PNG Is the Wrong Format for Photographs — The Real Cost in File Size Numbers

PNG is a genuinely excellent image format. For logos with transparent backgrounds, screenshots with text, UI elements, icons, and graphics with large solid-color regions, PNG delivers clean results at reasonable file sizes.

For photographs, it’s the wrong choice. And the mistake is more common than it should be, particularly on WordPress sites, CMS platforms where upload format defaults to whatever the source was, and anywhere a “just use the file you have” mentality prevails.

The File Size Math

Here’s what happens when you save a typical photograph—a 12 megapixel image of a person outdoors—in different formats at comparable quality:

The PNG version of a photo is typically 8–15× larger than a JPEG at the same visual quality. For a page with five images, that’s the difference between loading 5MB or 60MB of image data.

Why PNG Is Larger for Photographs

PNG uses lossless compression. Every pixel value is preserved exactly. The compression algorithm (DEFLATE) finds and encodes repeating patterns in the pixel data—which works well for images with large uniform regions (logos, diagrams, solid backgrounds) but poorly for photographs.

A photograph has high entropy—each pixel is different from its neighbors, reflecting real-world complexity in lighting, texture, color. There are almost no repeating patterns to compress. PNG can’t compress the complexity away; it just encodes it faithfully, producing a large file.

JPEG does something fundamentally different: it discards information that human vision doesn’t notice much, particularly fine detail, subtle texture variation, and high-frequency color changes. A quality-80 JPEG keeps everything that looks real to human eyes and throws away the rest. The result is 8–15× smaller than PNG with no perceptible quality difference at normal viewing sizes.

The “PNG Is Higher Quality” Misconception

PNG is lossless, JPEG is lossy—so PNG must be higher quality, right?

For graphics and screenshots, yes. For photographs displayed on screens at normal sizes, no.

The human visual system can’t perceive the 8-bit precision differences that PNG preserves over a high-quality JPEG. What you’re preserving is mathematical precision that neither displays nor print processes can render or that eyes would notice.

There are exceptions:

• Images that will be repeatedly edited and re-exported—PNG preserves the original precisely, preventing accumulating quality loss from multiple JPEG saves
• Source/master files in professional workflows—keep those as TIFF, PNG, or RAW
• Images with text embedded in them—JPEG’s compression creates visible artifacts around high-contrast text edges; PNG is better here

For finished photographs delivered to a website, social platform, email, or gallery: JPEG or WebP, not PNG.

What Happens on a Real Website

A photography portfolio or product page that uses PNG for all images loads dramatically slower than one using JPEG:

• Slower page load = higher bounce rate
• Slower page load = worse Core Web Vitals scores = lower search rankings
• Higher bandwidth costs if you’re paying for a CDN or image delivery service
• Mobile users on cellular connections experience long load times or broken images

For a product page with 8 PNG photos at 15MB each, that’s 120MB to load the product images alone. The same page with WebP images of the same photos is under 10MB.

Converting Existing PNG Photos to JPEG or WebP

If your site has existing PNG photographs that should be JPEG or WebP:

1. Export from the highest-quality original source (not re-compress the PNG, which would compound quality loss)
2. Use JPEG 80–85% for general web photography
3. Use WebP for modern browsers (better compression, same visual quality)
4. Update image references in your CMS, templates, or <img> tags

One caveat: if the PNG photo has a transparent background (an object cutout), you can’t simply convert to JPEG—JPEG doesn’t support transparency. Use WebP (with alpha channel) or keep as PNG-24 in that specific case.

The Right Format for the Right Job

The core rule: lossless for graphics, lossy for photographs. PNG has its place. Photographs aren’t it.

Convert your PNG photographs to JPEG or WebP with the free Image Compressor — choose your format and quality level, download immediately.