PNG vs JPG: The Differences That Actually Matter

Two opposite compression strategies

JPG is lossy: it divides the image into 8×8 blocks and discards visual information your eyes are bad at noticing — fine color detail first, then progressively more as quality drops. The discarded data is gone forever, but for photographs the trade is spectacular: a 10× size reduction with no visible difference is routine.

PNG is lossless: it compresses pixels the way ZIP compresses files — finding repetition and encoding it efficiently — and decompresses back to the exact original, every pixel bit-perfect. The catch: photographs have almost no exact repetition (every pixel of sky is slightly different), so PNG compresses them poorly. Flat-color graphics, by contrast, are nearly all repetition — and PNG crushes them.

Where JPG wins: photographs

Anything that came out of a camera — photos, scans of photos, screenshots of photos — belongs in JPG (or its modern successors WebP/AVIF). A 20-megapixel photo lands around 2–5 MB as a quality-85 JPG; the identical image as PNG is 30–60 MB for no visible benefit. Camera noise and smooth gradients are exactly what JPG's perceptual model handles well and what PNG's exact-repetition model can't compress at all.

Where PNG wins: graphics, text, and transparency

Screenshots of interfaces, logos, charts, diagrams, pixel art, anything with text: PNG. JPG's block-based compression smears sharp edges into visible halos — the fuzzy ringing you've seen around letters in over-compressed screenshots. PNG keeps every edge surgical, and on flat-color content it's usually smaller than JPG anyway.

PNG's second superpower is the alpha channel: real per-pixel transparency, which JPG simply doesn't have. A logo that must sit on any background needs PNG (or WebP/SVG) — converting it to JPG flattens the transparency onto a solid color, permanently.

The conversion question, honestly

JPG to PNG never improves quality — the detail JPG discarded is unrecoverable, and the file just gets several times larger. Convert that direction only when a tool demands PNG input or you need to add transparency in an editor. PNG to JPG is the genuinely useful direction: photographic PNGs (a common accident of screenshotting and exporting) shrink 5–10× with no visible change.

Both conversions take one drag-and-drop: PNG to JPG and JPG to PNG run in batch, client-side, with per-file results shown. And if the goal is just a smaller file of the same format, the PNG compressor handles that without switching formats at all.

The thirty-second decision rules

Came from a camera → JPG. Has text, sharp edges, or flat colors → PNG. Needs transparency → PNG. Going on a website you control → consider WebP, which does both jobs smaller. Sending to a person or an upload form → JPG for photos, PNG for screenshots — both are accepted literally everywhere, which is why the two formats have outlived a dozen 'replacements'.