Every image on your website is a tradeoff between three things: file size, visual quality, and compatibility. Pick the wrong format and you're shipping 10× the bytes for the same picture — which means slower pages, worse Core Web Vitals, and a lower Google ranking.
In 2026 the practical choice has narrowed down to three modern formats: WebP, PNG, and AVIF (with legacy JPEG hanging around as the fallback). Here's the plain-English breakdown of each — with real numbers — so you never pick the wrong one again.
The one-sentence summary
- WebP — the best default. 25–35% smaller than JPEG, supports transparency, works in every modern browser.
- PNG — lossless and pixel-perfect, but huge. Reserve it for logos, screenshots, and text.
- AVIF — the smallest files of all, but encodes slower and has slightly newer browser support.
Size: the numbers that actually matter
Let's start with the same 2.1MB JPEG photograph and see what happens when we re-save it in each format at equal visual quality:
| Format | Typical size | vs. JPEG |
|---|---|---|
| JPEG (baseline) | ~2.1MB | 100% |
| WebP | ~186KB | −91% |
| AVIF | ~102KB | −95% |
That's not a typo. A single photo that starts at 2.1MB drops to under 200KB as WebP and just over 100KB as AVIF — at a quality level most people can't distinguish from the original.
The reason comes down to how each format compresses. I've written a full side-by-side of WebP vs PNG and AVIF vs WebP vs JPEG if you want the deep detail, but the short version is:
- PNG is lossless. It stores every pixel exactly, which is why a photograph (full of gradients and fine color detail) barely shrinks at all. A 4MB photo stays ~4MB as PNG.
- WebP and AVIF are lossy — they discard data the human eye won't miss, tuned to how we actually perceive images.
That one difference — lossless vs. lossy — is behind 90% of the "which format?" confusion.
When to use each format
PNG: when every pixel has to be exact
PNG's lossless guarantee makes it unbeatable for screenshots, logos, icons, UI elements, and anything with text or hard edges. Lossy formats introduce slight "ringing" artifacts around high-contrast boundaries, which is why a logo saved as JPEG or lossy WebP looks soft around the edges.
The tradeoff is size: a 2.5MB PNG screenshot is common. Before shipping PNGs, always run them through a lossless optimizer — it re-encodes the file more efficiently with zero pixel change, typically saving 20–60%. My comparison of WebP vs PNG covers exactly when PNG's lossless guarantee is worth the extra bytes.
WebP: the modern default for almost everything
Developed by Google, WebP is the "best of both worlds" format: lossy compression that's 25–35% smaller than JPEG at the same quality, plus transparency support (which JPEG lacks) and a lossless mode.
Browser support passed 96% years ago — every modern browser renders it. For photos, product images, and even graphics with transparency, WebP is the safe, high-impact default. If you've got a library of PNGs or JPEGs, converting them is the single fastest page-weight win you'll find.
AVIF: smallest, but newer
AVIF (AV1 Image File Format) produces the smallest files — roughly 30–50% smaller than JPEG and another 20–30% smaller than WebP. A 2.1MB JPEG becomes about 102KB.
The tradeoffs: it encodes noticeably slower (a few hundred milliseconds per image), and while Chrome, Firefox, and Safari all support it, that support is a bit newer than WebP's. For a build pipeline where you convert once and cache forever, AVIF wins. For one-off conversions, WebP is usually the more practical choice. The full AVIF vs WebP vs JPEG breakdown explains when each wins.
JPEG: the compatibility fallback
JPEG has 100% universal support and refuses to die for exactly that reason. But it's the largest of the lossy formats. In 2026, you should only reach for JPEG when you genuinely need to support very old browsers — otherwise WebP or AVIF is strictly better.
How to convert between formats (in your browser, no upload)
You don't need Photoshop or a server to switch formats. A browser-based tool can convert everything locally — your images never leave your device, and there's no account or upload queue:
- Convert PNG to WebP — the biggest single win for photo-heavy pages
- Convert WebP to PNG — when you need pixel-perfect back
- Convert WebP to JPG — for maximum compatibility
- Convert AVIF to WebP — shrink further or maximize support
- Convert to WebP — the catch-all converter
Here's the flow I'd recommend for any website:
- Pick the format — photos and most graphics → WebP; logos/screenshots/text → PNG; absolute smallest in a pipeline → AVIF.
- Resize to what you actually display — a 4000×3000 photo only needs to be 1200–1600px on the web. Resizing first often cuts 70%+ before any compression.
- Convert and compress — let the tool handle the quality tradeoff. For photos, 75–85% quality is the "sweet spot" where nobody notices the difference.
If you want the complete decision framework, start with my guide to the best image format for the web — it walks through every format with real numbers.
The bottom line
The format wars are over, and the winner is situational: WebP for almost everything, PNG for pixel-perfect graphics, AVIF for the smallest possible files. Pick based on what the image is, not on habit — and your pages get smaller and faster for free.
I built CompressFast to do all of this in the browser: no upload, no account, 100% local. Drop in up to 30 images, pick your format, and download a ZIP of the results.
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