JPEG vs PNG: Which Format Should You Choose?

The Core Difference: Lossy vs Lossless

JPEG uses lossy compression — it permanently discards image data to achieve smaller files. The discarded data is chosen to be least perceptible to human vision (we are more sensitive to brightness than colour, more sensitive to large areas than fine detail), but the data is gone after saving. Every re-save of a JPEG discards additional data.

PNG uses lossless compression — it reorganises pixel data into a smaller representation, but every pixel is stored exactly. The decoded image is bit-for-bit identical to the original. You can save a PNG a thousand times and the 1000th save is identical to the first.

This difference drives every other difference between the formats.

Where JPEG Wins

Photographs and complex scenes. JPEG's lossy algorithm was specifically designed for photographic content — images with millions of gradual colour transitions. In this territory, JPEG achieves 60–90% size reductions with losses that are invisible at normal viewing distances.

File size. A photograph at JPEG quality 85 is typically 5–15× smaller than the same image as PNG-24. For a 2000×1333px lifestyle photo:

• JPEG quality 85: ~300KB
• PNG-24: ~2.8MB

At scale — a product page with 12 images, a blog post with 8 photos — this difference directly determines page load speed and hosting costs.

Progressive loading. JPEG supports progressive loading: the image appears blurry and sharpens as more data arrives. This improves perceived performance for large images on slow connections.

Where PNG Wins

Transparency. PNG supports alpha transparency — every pixel has a transparency value from 0 (invisible) to 255 (fully opaque). This enables smooth edges, soft shadows, and images that composite cleanly against any background. JPEG cannot store transparency at all; transparent areas become solid white or black.

Logos, icons, and text. JPEG's DCT compression operates on 8×8 pixel blocks. When those blocks contain sharp edges — the edge of a letter, a logo against a white background — the compression creates visible ringing artifacts (blurry, discoloured halos). PNG stores those edges perfectly because it does not discard any data.

Screenshots. Screenshot content contains UI text, sharp interface edges, and often flat colours — exactly the content JPEG handles worst. A screenshot saved as JPEG at quality 85 will have visible compression artifacts around every text character. PNG-24 preserves the screen content exactly.

Images edited and re-saved multiple times. Because PNG is lossless, repeated editing and saving does not degrade quality. JPEG degrades cumulatively.

Side-by-Side Comparison Table

Decision Flowchart

Use this flowchart to choose:

1. Does the image need a transparent background?

→ Yes: Use PNG (or WebP, which also supports transparency)

→ No: Continue

2. Is it a photograph, gradient, or complex natural scene?

→ Yes: Use JPEG (or WebP for 25-35% better compression)

→ No: Continue

3. Does it contain text, sharp edges, or flat colours (logo, icon, screenshot)?

→ Yes: Use PNG

→ No: Use JPEG as the safe default

4. Is file size critical for web performance?

→ Yes: Consider WebP — it beats both JPEG and PNG in compression while supporting transparency

File Size Reality with Real Numbers

The difference is not abstract. Here are measurements from common real-world image types:

Photograph (2000×1333px lifestyle image):

• JPEG quality 85: 312 KB
• PNG-24: 2.8 MB → PNG is 9× larger
• WebP quality 80: 198 KB → WebP is 37% smaller than JPEG

Logo (vector-derived, 400×200px, flat colours, transparent background):

• PNG-8: 12 KB
• PNG-24: 28 KB
• JPEG quality 90 (no transparency): 18 KB with visible edge artifacts
• SVG original: 4 KB → SVG is the best option for logos

Screenshot (1440×900px, web UI):

• PNG-24: 890 KB
• JPEG quality 85: 420 KB (50% smaller, but visible artifacts on text)
• WebP quality 85: 310 KB (65% smaller than PNG, clean text)

JPEG Artifacts Explained

JPEG artifacts are the visible side effects of lossy compression pushed too far. Understanding them helps you choose the right quality setting.

Block artifacts: The most recognizable JPEG artifact. Because DCT compression works on 8×8 pixel blocks, heavy compression makes those blocks visible — the image looks like it was divided into a grid of squares with different colour tones in each.

Ringing artifacts: Around sharp edges (text, logo outlines, high-contrast transitions), JPEG creates a halo of discoloured pixels. Text that should have a clean black edge develops a blurry fringe. This is why JPEG is wrong for any image containing text.

Colour banding: In areas of subtle colour gradients (sky, smooth skin tones, gradients in UI design), JPEG can introduce visible steps between colours rather than smooth transitions. Most noticeable at low quality settings.

The quality sweet spot: For web photographs, 75–85% eliminates all practically visible artifacts for the vast majority of images. Going below 75% requires careful inspection before publishing.

Converting Between JPEG and PNG

Converting JPEG to PNG makes the file larger and lossless — but it cannot recover data already discarded by JPEG compression. The output PNG is a lossless copy of a lossy original. This is useful when you need to make further edits to a JPEG without further quality loss, but it is not a quality improvement.

Converting PNG to JPEG discards the alpha channel (transparent areas become solid) and introduces lossy compression for the first time. The output is smaller but cannot be converted back to the original quality.

The practical takeaway: match the format to the original content and intended use. Converting between formats is often the wrong tool — the right answer is usually to start from the original source file in the correct format.