Raster vs. vector: the fundamental split
Every image format is either raster (a grid of pixels, each with a fixed color — PNG, JPEG, WebP, GIF) or vector (mathematical shapes and paths — SVG). Raster images have a fixed resolution; scale one up and it blurs or pixelates, because there's no more detail to reveal, only the existing pixels stretched. Vector images are resolution-independent — an SVG icon rendered at 16px or 1600px is recalculated from the same underlying math, so it stays crisp at any size. This is why icons and logos belong in SVG, and photos belong in raster formats — a camera photo has no underlying "shapes" to vectorize.
Lossy vs. lossless compression
Within raster formats, compression falls into two categories:
- Lossless (PNG, GIF, WebP-lossless): the decompressed image is pixel-for-pixel identical to the original. Ideal for screenshots, text, logos, and anything with sharp edges or flat color regions, where lossy artifacts (blurring, ringing) would be visible.
- Lossy (JPEG, WebP-lossy): compression discards information the algorithm judges "less visually important" (typically high-frequency detail), producing much smaller files at the cost of some quality loss. Ideal for photographs, where the human eye is less sensitive to the exact discarded detail.
Format by format
PNG — lossless, supports full 8-bit alpha transparency, no quality degradation on repeated saves. Best for screenshots, UI graphics, and anything needing a transparent background. Larger files than JPEG for photographic content.
JPEG — lossy, no transparency support, adjustable quality/size tradeoff. Best for photographs where file size matters more than pixel-perfect fidelity. Repeated edit-and-resave cycles compound quality loss (generation loss) since each save re-compresses.
WebP — Google's format supporting both lossy and lossless modes, plus alpha transparency in both. Typically 25–35% smaller than an equivalent-quality JPEG (lossy mode) or PNG (lossless mode), which is why it's become the default choice for web delivery. The tradeoff is historically weaker support in some older tools/browsers, though modern browser support is now near-universal.
SVG — vector, XML-based, infinitely scalable, and editable as text (you can hand-write simple SVGs). Ideal for icons, logos, and illustrations built from shapes rather than continuous-tone photography. Not suitable for photographs — there's no efficient way to vectorize a photo's pixel-level detail.
| Format | Type | Compression | Transparency | Best for |
|---|---|---|---|---|
| PNG | Raster | Lossless | Yes (full alpha) | Screenshots, UI graphics, logos |
| JPEG | Raster | Lossy | No | Photographs |
| WebP | Raster | Both | Yes | General web delivery (replaces PNG/JPEG) |
| SVG | Vector | N/A (math, not pixels) | Yes | Icons, logos, illustrations |
Common mistakes
- Saving a photo as PNG "for quality." PNG's lossless compression doesn't help a continuous-tone photo the way it helps flat-color graphics — the file balloons in size for negligible visible benefit over a high-quality JPEG or WebP.
- Repeatedly re-saving a JPEG during edits. Each save re-compresses and discards more detail (generation loss); keep a lossless master (PNG or the original) and only export to JPEG once, at the end.
- Trying to scale up a raster image and expecting it to stay sharp. Upscaling a raster image invents new pixels via interpolation; it can't recover detail that was never captured. Only vector formats scale losslessly.
- Using SVG for photographs. Vector formats represent shapes, not continuous pixel detail — a "vectorized" photo is either a poor approximation or secretly just an embedded raster image inside the SVG wrapper.
FAQ
Is WebP always better than PNG and JPEG?
For file size at equivalent visual quality, yes in most cases — the main reason to still choose PNG/JPEG directly is compatibility with older tooling or specific pipeline requirements, which is increasingly rare.
Can I convert a raster image to SVG and get a scalable version?
Only via "vectorization," which traces shapes/edges and is an approximation — it works reasonably for simple logos and icons, but not for photographs, where it either fails or just embeds the raster data.
Why does my PNG look fine but the file size is huge?
PNG's lossless compression doesn't reduce photographic detail — a photo saved as PNG keeps every pixel's original color information, so file size stays close to the pixel-count × color-depth, unlike JPEG or WebP which actively discard imperceptible detail.
Does converting JPEG to PNG restore lost quality?
No — once JPEG's lossy compression discards detail, converting to a lossless format afterward just locks in the already-degraded image at a larger file size; it can't recover the original data.
Convert between PNG, JPEG, WebP, and more directly in your browser with the Image Converter — no upload required.