JPG vs PNG: Which Image Format Should You Use?

If you have ever wondered whether to save an image as JPG or PNG, you are not alone. These two formats dominate the web, yet they behave very differently under the hood. Choosing the wrong one can mean unnecessarily large files, visible compression artifacts, or a broken transparent background. This article explains the technical difference in plain language so you can make the right call every time.

The Core Difference: Lossy vs Lossless

JPG (also written JPEG) uses lossy compression. When you save a JPG, the encoder discards some image data — specifically, subtle color transitions that the human eye is least sensitive to. The result is a much smaller file, but the original pixel data is permanently altered. Each time you re-save a JPG you lose a little more quality, a process sometimes called "generation loss."

PNG uses lossless compression. Every pixel is stored exactly as it was captured. The file is larger than an equivalent JPG, but it can be decompressed back to a perfect copy of the original. There is no generation loss — you can open and re-save a PNG indefinitely without degrading it.

Transparency: A Decisive Factor

PNG supports an alpha channel, which controls the transparency of each pixel from fully opaque to fully invisible. This is essential for logos, icons, UI elements, and any graphic you want to place on top of a different background. JPG has no transparency support at all — transparent areas are filled with a solid color (usually white or black) when you save as JPG.

File Size in Practice

For a typical full-color photograph (3000 × 2000 pixels), a high-quality JPG at 80% quality might be around 1–2 MB, while the same image saved as PNG could be 8–15 MB. The gap narrows for images with flat colors, sharp edges, and few gradients — a screenshot of a webpage or a diagram might only be 20–30% larger as PNG than as JPG.

The reason is that PNG compression works by finding repeated patterns in the pixel data. A photograph has millions of subtly different color values, so repetition is rare and the lossless algorithm cannot shrink it much. A screenshot with large solid-color regions has enormous amounts of repetition, so PNG compresses it very efficiently.

When to Use JPG

• Photographs and realistic images with smooth color gradients
• Hero images, banners, and backgrounds on websites
• Social media profile photos and cover images
• Scanned documents that contain photographs
• Any situation where file size matters more than pixel-perfect accuracy

When to Use PNG

• Logos, icons, and illustrations with transparent backgrounds
• Screenshots and screen recordings
• Images with text, sharp edges, or flat areas of color
• Graphics you will edit and re-save multiple times
• Images where absolute color accuracy is required (e.g., product photography retouching)

Quality Settings and Compression

JPG encoders expose a quality slider, typically 0–100. A setting of 75–85 is a sweet spot for most web use: the visual difference from 100% quality is negligible, but the file size can be 60–80% smaller. Below 60% you will start seeing blocky compression artifacts called "mosquito noise" around edges and high-contrast areas.

PNG has no quality slider because it is lossless. The only tuning parameter is the compression level, which controls how hard the encoder works to find repeating patterns. Higher compression = same image quality, smaller file, more CPU time. Most tools default to a balanced level (around 6 on a 0–9 scale) that is perfectly adequate.

Progressive vs Baseline JPG

JPGs can be saved in baseline (top-to-bottom) or progressive mode. Progressive JPGs appear blurry then sharpen as they load, which feels faster to users even though the file size is nearly identical. Most modern image editors default to progressive for web exports.

What About WebP?

WebP is a newer format developed by Google that offers better compression than both JPG and PNG, with transparency support. It is supported by all major modern browsers. If you need the smallest possible files for the web, WebP is worth considering — but JPG and PNG remain universally compatible with every device and application.

Converting Between Formats

Converting from PNG to JPG is straightforward and usually safe for photographs. Converting from JPG to PNG does NOT recover lost quality — the artifacts are baked in. You will just get a larger file with the same artifacts. Always start from the highest-quality source you have.