The fundamental split: raster vs vector
Before comparing formats, there is one concept that explains most of the differences. Images come in two fundamentally different kinds. Raster images are made of a grid of coloured pixels, like a mosaic. Photographs are raster. If you zoom in far enough, you see the individual squares. Vector images are made of mathematical instructions — 'draw a circle here, fill it with this colour, add this line'. Because they are instructions rather than fixed pixels, vectors can scale to any size without ever becoming blurry.
JPG, PNG, and WebP are all raster formats. SVG is a vector format. That single distinction determines most of when you should use each one.
JPG: for photographs
JPG (also written JPEG) is the format built for photographs. It uses lossy compression, which means it throws away some detail the human eye is unlikely to notice in exchange for dramatically smaller files. For a photo with thousands of subtle colour gradients — a landscape, a portrait, a product shot — JPG produces a small file that still looks good.
Its weakness is sharp edges and flat colour. If you save a logo, a screenshot with text, or a diagram as JPG, you will often see faint smudges and halos around the crisp lines. That is the lossy compression struggling with hard edges. JPG also does not support transparency, so it cannot sit cleanly over a coloured background.
Use JPG when
- The image is a photograph or has photographic detail.
- You do not need transparency.
- Small file size matters more than pixel-perfect edges.
PNG: for graphics, text, and transparency
PNG uses lossless compression, meaning it preserves every pixel exactly. That makes it the right choice for images with sharp edges and flat areas of colour: logos, icons, screenshots, diagrams, and anything containing text. PNG also supports transparency, so a logo can sit over any background without a white box around it.
The trade-off is file size. For a photograph, a PNG can be several times larger than the equivalent JPG, because lossless compression cannot discard the fine detail that makes photos heavy. Using PNG for photos is one of the most common causes of needlessly slow web pages.
Use PNG when
- The image has sharp edges, flat colour, or text.
- You need transparency.
- Exact pixel fidelity matters more than the smallest file.
WebP: the modern all-rounder
WebP is a newer format designed to replace both JPG and PNG. It supports both lossy and lossless compression and handles transparency. In most cases it produces files noticeably smaller than the equivalent JPG or PNG at the same visual quality. For web use, converting images to WebP is one of the easiest ways to speed up a page without any visible loss.
The catch is compatibility. While every current browser supports WebP, some older software, email clients, and design tools do not. That is why a converter to turn WebP back into PNG is still useful — you might receive a WebP file and need it in a format an older program accepts.
Use WebP when
- The image is going on a website and page speed matters.
- You want smaller files than JPG or PNG at similar quality.
- Your audience uses modern browsers (which is almost everyone now).
SVG: for logos, icons, and anything that must scale
SVG is the odd one out, because it is a vector format. An SVG file is actually a small text document describing shapes. Because it is instructions rather than pixels, an SVG logo looks perfectly crisp whether it is displayed at 16 pixels wide in a menu or printed two metres across on a banner. It never pixelates, and the file is often tiny because describing a few shapes takes very little data.
SVG is ideal for logos, icons, and simple illustrations, but it is the wrong tool for photographs. You cannot meaningfully store a photo as vector instructions. SVG also needs converting to a format like PDF when a printer or client requires a fixed-page document rather than a web graphic.
Use SVG when
- The graphic is a logo, icon, or simple illustration.
- It needs to scale to many sizes without losing sharpness.
- The source is already vector artwork from a design tool.
A quick decision guide
- Photograph for the web → WebP, or JPG if you need broad compatibility.
- Logo or icon that must scale → SVG.
- Screenshot, diagram, or anything with transparency → PNG, or WebP for smaller size.
- Received a WebP an old program won't open → convert to PNG.
- Need a vector graphic as a fixed document → convert SVG to PDF.
Getting the format right is usually more impactful than any amount of compression. A logo saved as SVG will always beat the same logo saved as a heavily optimised JPG, and a photo saved as WebP will always beat the same photo saved as a bloated PNG. Start with the right format, then optimise within it.