PNG vs JPG File Size Comparison: Which Format Should You Use?

PNG vs JPG: The Complete Comparison

Choosing between PNG and JPG (JPEG) is one of the most common decisions in digital media. Both formats have distinct advantages, and understanding when to use each can save significant bandwidth and storage.

How JPEG Works

JPEG uses lossy compression based on the discrete cosine transform (DCT). It exploits the human visual system's greater sensitivity to brightness changes than color changes:

This process allows JPEG to achieve very high compression ratios, typically reducing photos to 10-20% of their uncompressed size.

How PNG Works

PNG uses lossless compression based on the DEFLATE algorithm:

PNG also supports transparency (alpha channel) and can store 8-bit or 16-bit color depth.

File Size Comparison

Here's how the formats typically compare for different types of images:

Photographs

For a typical 1920x1080 photograph:

JPEG is clearly superior for photographs, achieving 10-20x compression while PNG barely reduces the size.

Graphics and Logos

For a 500x500 logo with flat colors:

PNG excels here because flat colors compress extremely well with DEFLATE, and JPEG introduces unwanted artifacts around sharp edges.

Screenshots

For a 1920x1080 screenshot:

PNG is preferred for screenshots because it preserves text sharpness, though the file size is larger.

When to Use JPEG

JPEG is the best choice when:

When to Use PNG

PNG is the best choice when:

The WEBP Alternative

Modern web development increasingly uses WEBP, which combines advantages of both:

Converting Between Formats

JPEG to PNG

Converting JPEG to PNG makes the file larger without improving quality. The quality loss from JPEG compression is permanent. Only convert if you need transparency support.

PNG to JPEG

Converting PNG to JPEG reduces file size significantly for photographs but:

Either to WEBP

Converting to WEBP typically provides the best of both worlds. Use tools like Compressly for automatic format optimization.

Optimization Tips for Each Format

JPEG Optimization

PNG Optimization

Best Practices for Web Use

Use Both Formats Strategically

A well-optimized website uses different formats for different purposes:

Implement Format Detection

Serve the most efficient format based on browser support using the picture element or image CDN auto-format features.

Always Compress

Regardless of format, always compress your images before uploading. Use Compressly to automatically optimize any image format with the best compression settings.

Conclusion

Neither PNG nor JPG is universally better. The right choice depends on your specific image content and requirements. Use JPEG for photographs and complex images, PNG for graphics and transparency, and consider WEBP as a modern alternative that works well for both.

Optimize any format with Compressly's image compressor for the best balance of quality and file size.