JPG vs PNG: which should you use?

JPG, more formally JPEG, compresses images by transforming blocks of pixels and discarding detail that is less visible to human vision. That works well for natural photographs with gradients and texture. It works poorly for sharp text, flat icons, and screenshots because block artifacts and color ringing appear around edges.

PNG stores exact pixel data after applying predictive filters and lossless compression. If a PNG is decoded and re-encoded losslessly, the visual pixels can remain unchanged. That makes PNG a safer source format for graphics, but it can become very large for photos.

PNG supports alpha transparency. This is why logos, cutouts, favicons, and UI overlays often use PNG. JPG has no alpha channel, so transparent areas must be filled with a background color during export. That background may look wrong when placed on another page.

If you convert PNG to JPG, choose the background color deliberately. White is common for documents, but black, transparent checkerboards, or unexpected matte colors can appear when the exporter guesses. For product images, test the final placement rather than only opening the standalone file.

Screenshots with small text are usually better as PNG because text edges remain crisp. A JPG screenshot can look acceptable at a glance and still fail OCR or become unpleasant to read after resizing. For scanned paper, the best choice depends on content: text-only scans often belong in PDF with OCR, while photo-heavy scans may be fine as high-quality JPEG inside PDF.

For command-line checks, file -I image.jpg only tells you the media type, not whether the quality is good. Inspect at full size, zoom on text edges, and compare file sizes after saving with realistic settings.

Repeatedly opening and saving a JPG causes generation loss when the editor re-encodes it. The damage may be small after one save and obvious after many saves. PNG does not add that kind of loss, although edits such as resizing, color conversion, or flattening still change the image.

Keep a PNG, TIFF, PSD, or original camera file as the editing master when quality matters. Export JPG copies for email, web posts, or systems that require JPEG. Do not use JPG as the only archive for annotated screenshots or graphics with text.

Convert JPG to PNG when a tool requires PNG input or when you need a lossless container for the already-decoded pixels. The conversion does not restore detail removed by JPEG compression. Convert PNG to JPG when the image is photographic, has no transparency, and must be smaller or accepted by a JPEG-only destination.

For documents, converting images to PDF is often better than trading JPG and PNG back and forth. A PDF can hold multiple pages, combine image and text layers, and preserve page size.

A useful rule is to ask whether the image is a photograph or a graphic. Photographs usually tolerate JPEG compression because natural texture hides some loss. Graphics with text, flat fills, and hard edges expose JPEG artifacts quickly. Mixed images, such as a product photo with text labels, need visual checking.

For archives, keep the capture format or a lossless master. Delivery copies can be JPG, PNG, WebP, or PDF depending on the recipient. Separating the master from the delivery file prevents a small upload requirement from becoming a permanent quality decision.