PNG to WebP: When It Helps and When It Doesn't

PNG is everywhere on the web. It's the default for screenshots, the standard for transparent UI assets, and the natural fallback any time someone says "I need a clean export."

It's also surprisingly fat. A 1920×1080 screenshot can easily be 1–2 MB as PNG, and that's just for one image. WebP supports the same things PNG does (lossless compression, transparency, sharp edges) and routinely produces files 30–60% smaller.

So the question is: should you just convert all your PNGs to WebP?

Not quite. Here's how to think about it.

What WebP gives you that PNG doesn't

Three things, all useful:

1. Lossy with transparency. PNG only does lossless compression, so transparent UI assets stay big. WebP supports lossy + alpha, which can shrink a transparent button from 80 KB to 12 KB with no visible quality drop.
2. Better lossless compression. Even in lossless mode, WebP usually beats PNG by 20–30% on the same image. The encoder is just newer and smarter.
3. Lower decode cost. WebP is fast to decode. Browsers handle WebP without the historical performance hits some older PNGs caused.

When WebP wins

• UI screenshots and design exports. Almost always smaller. A 200 KB PNG screenshot becomes a 60 KB WebP at lossless quality, or a 25 KB WebP at quality 85.
• Buttons, icons, and decorative assets with transparency. This is where the gains are largest: PNGs with alpha are the worst case for PNG's compression model and the best case for WebP's.
• Photo-style content currently shipped as PNG. People sometimes ship PNG photos because they want zero compression. WebP at quality 90 still looks identical to the eye and is 70–80% smaller.

When PNG is fine to keep

• Tiny images, under ~5 KB. WebP's per-file overhead can make a 2 KB favicon larger as WebP than as PNG. The savings show up on bigger files.
• Anything you're shipping to a non-web context. Native macOS apps, Windows installers, Android resource bundles. Many of these still expect PNG, and the format is universally supported in design tools.
• When the source has been optimized already. A PNG that's already been run through pngcrush or oxipng with palette quantization may be roughly the same size as a WebP. The savings are biggest on raw, unoptimized PNGs.
• When you want lossless preservation forever. PNG is mature and decoded by everything. If this image is going in a long-term archive, the universality is worth a few extra kilobytes.

When you should be cautious

• Anything legal, medical, or evidentiary. A medical scan or a screenshot for a legal record shouldn't go through any lossy step. Keep PNG, or convert to lossless WebP only.
• Pixel art and small graphics. Lossy WebP introduces subtle blurring around hard edges, which is the entire point of pixel art. Use lossless WebP, or just keep the PNG.
• Images with embedded text rendered as part of the image. Lossy compression breaks text edges first. Keep PNG, or convert lossless.

How much smaller will it actually be?

Some real numbers from typical web assets:

The 64×64 icon shows the small-image case where the savings are minimal. Everything else shows the typical 30–80% reduction.

A practical rule

If a PNG is larger than ~50 KB and is being shown on the web, convert it to WebP. The savings are almost always worth it.

If it's smaller than that, or if it's part of a non-web pipeline, leave it. The compression gains aren't worth the extra format in your build.

Compatibility

In 2026, WebP is supported by every browser anyone is actually using. Safari, Chrome, Firefox, Edge, all natively. The format has been universal since 2020. You don't need a <picture> fallback for WebP unless your audience is genuinely on browsers older than five years.

Convert PNGs to WebP in your browser with OmegaPix's PNG to WebP converter. The conversion runs in WASM in your browser tab, no upload, no waiting in someone's queue. Drop a PNG (or a folder of them), pick a quality, download the WebPs.