Three formats cover almost every image on the web. Choosing correctly can cut your page weight in half without anyone noticing a difference in quality.
Almost every image you encounter online is a JPG, a PNG, or a WebP. They are not interchangeable. Each was designed for a different kind of picture, and using the wrong one is the single most common cause of unnecessarily heavy web pages and disappointing image quality.
JPG: built for photographs
JPG — also written JPEG — dates from 1992 and remains the default for photographic images. It uses lossy compression built around how human vision works: our eyes are far more sensitive to changes in brightness than to changes in colour, and far less sensitive to fine detail in busy areas than in flat ones. JPG throws away the information we are least likely to notice.
Strengths
- Exceptional compression for photographs and any image with smooth gradients and organic detail.
- Universal support across every browser, operating system, camera, and application.
- Adjustable quality, giving you a direct dial between file size and fidelity.
Weaknesses
- No transparency support at all.
- Visible ringing and blocking artefacts around sharp edges, which makes it poor for text, logos, and line art.
- Lossy and generational — every re-save degrades the image further.
Use JPG for photographs, hero images, product shots, and anything camera-originated. Quality 80 to 85 is the practical sweet spot; the difference from quality 100 is usually invisible while the file is a fraction of the size.
PNG: built for graphics and precision
PNG uses lossless compression, which means the decoded image is bit-for-bit identical to the original. Nothing is discarded, ever. It also supports a full alpha channel, giving you 256 levels of transparency per pixel rather than the crude on-or-off transparency of older formats.
Strengths
- Perfectly lossless — ideal for screenshots, diagrams, and any image that will be edited repeatedly.
- True alpha transparency, essential for logos and overlay graphics.
- Compresses flat colour regions and sharp edges extremely efficiently.
Weaknesses
- Very large files for photographic content — often five to ten times a comparable JPG.
- No animation in standard PNG.
Use PNG for logos, icons, screenshots, UI mockups, charts, diagrams, and anything requiring transparency or pixel-exact reproduction. Never use PNG for a photograph on a web page unless you have a very specific reason.
WebP: the modern compromise
WebP, developed by Google and now supported by every current browser, offers both lossy and lossless modes plus transparency and animation in a single format. In practice it delivers roughly 25 to 35% smaller files than JPG at visually equivalent quality, and often 20 to 30% smaller than PNG for graphics.
Strengths
- Lossy and lossless in one format, so it replaces both JPG and PNG.
- Transparency even in lossy mode — something JPG cannot do at all.
- Substantially smaller files at equivalent perceived quality.
- Supported in Chrome, Edge, Firefox, Safari, and all modern mobile browsers.
Weaknesses
- Weaker support in older desktop software and some print workflows.
- Not accepted by every platform, marketplace, or content management system.
- Less familiar to non-technical recipients receiving a file by email.
Head-to-head at a glance
- Photograph on a website: WebP first choice, JPG as the safe fallback.
- Logo with transparency: WebP lossless or PNG.
- Screenshot for documentation: PNG.
- Email attachment for a non-technical recipient: JPG.
- Print production: neither — use TIFF or a high-quality JPG at full resolution.
- Icon or favicon: PNG, generated at multiple sizes.
How to test which format wins for your image
Theory only takes you so far, because the answer depends on the specific image. A flat illustration with six colours behaves nothing like a textured landscape photograph. The reliable method is to export the same image in each candidate format and compare both the file size and the visual result side by side.
You can do this in seconds with the Image Converter, which converts between PNG, JPG, and WebP directly in your browser. Then use the Image Compressor to sweep through quality levels and find the lowest setting that still looks right at full size.
What to look at when comparing
- Edges of text and logos — the first place JPG artefacts appear.
- Smooth gradients such as skies, which can develop visible banding.
- Areas of flat colour, where lossy compression sometimes introduces subtle blotches.
- Fine repeating texture like fabric or foliage, where detail loss shows up as mush.
A word on dimensions
Format choice matters, but pixel dimensions matter more. Serving a 4000-pixel-wide photograph into a 800-pixel-wide layout wastes roughly 96% of the data transferred, and no format can rescue that. Resize images to the largest size they will actually be displayed at — allowing for high-density displays, which typically means twice the CSS dimension — using the Image Resizer before you worry about encoding.
The decision in one sentence
If the image is a photograph, reach for WebP with a JPG fallback; if it has transparency, sharp edges, or must remain pixel-perfect, reach for PNG or lossless WebP; and in every case, resize before you compress. Follow that and your images will be both smaller and better looking than the majority of what is published online.