Compress PNG

PNG (Portable Network Graphics) was created in 1996 by the W3C as a patent-free alternative to GIF after the Unisys LZW patent controversy. It uses DEFLATE compression (a combination of LZ77 and Huffman coding) to achieve lossless compression, meaning the decompressed image is bit-for-bit identical to the original. PNG supports 24-bit true color, 8-bit grayscale, and indexed color modes, plus a full 8-bit alpha channel for smooth transparency — a major advantage over GIF's single-bit transparency.

PNG compression operates in two stages: filtering and DEFLATE. First, each row of pixels is filtered using one of five prediction methods (None, Sub, Up, Average, Paeth) to exploit pixel-to-pixel redundancy. The filtered data is then compressed with DEFLATE, which combines dictionary-based LZ77 matching with Huffman entropy coding. Advanced tools also optimize the color palette for indexed-color PNGs, remove non-essential chunks (tEXt, iTXt, tIME), and test multiple filter/compression strategies to find the smallest output.

Compress PNG files whenever you need to reduce bandwidth and improve load times without sacrificing image fidelity. Common scenarios include website assets (logos, icons, UI elements), screenshots for documentation or support tickets, social media graphics with text overlays, and CMS uploads where storage quotas matter. PNG compression is especially impactful for images with large flat-color regions or repetitive patterns, where DEFLATE achieves the highest compression ratios.

Always strip metadata (EXIF, ICC profiles) unless color accuracy is critical. Use indexed color (8-bit palette) instead of true color when your image has fewer than 256 colors — this alone can cut size by 60-70%. Prefer PNG over JPEG for images with text, line art, or transparency; switch to WebP or JPEG for photographs where lossy compression is acceptable. Resize images to their display dimensions before compressing, and consider serving WebP with a PNG fallback for maximum browser compatibility and performance.