PNG is the universal lossless raster format: pixel-perfect reproduction, full alpha channel, supported by every browser, editor, and OS since the late 1990s. Convert to PNG when you need a mathematically identical result (UI mockups, logos, technical diagrams, screenshots), transparency (buttons, icons, product cutouts), or wide compatibility (any tool that can't read WebP or AVIF). This tool takes any input format and produces a PNG, then passes it through oxipng — the same optimizer used in production by GitHub, Google, and every serious asset pipeline — to strip metadata and re-pack the bytes losslessly. Effort level 6 (max) can shave 5–15% off the raw PNG output with zero pixel changes.
When to choose PNG in 2026
Choose PNG for anything that needs to be lossless: UI mockups, logos, icons, technical diagrams, screenshots, product cutouts with sharp edges, and anything you'll re-edit later. PNG's alpha channel is pixel-perfect, unlike JPEG which has none, or WebP-lossy which slightly softens alpha edges. The tradeoff is size — PNG is 2–5× larger than JPEG for photographic content and 1.5–2× larger than WebP-lossless. For photos meant for the web, prefer WebP or AVIF; for design assets and screenshots, PNG is the right choice.
oxipng — why the tool's output is smaller
Most PNG encoders (browsers, image editors, screenshot tools) produce PNGs that are 5–15% larger than they need to be because they use fast, generic zlib compression. oxipng is a specialized PNG optimizer that tries multiple compression strategies (different filter types, block sizes, zopfli-level entropy coding at max effort) and picks whichever produces the smallest output. This tool runs oxipng at level 6 (max) by default — the same effort GitHub uses when optimizing repository README images. Every byte matters when your site's LCP is measured against Core Web Vitals thresholds.
Handling JPEG and photo input
Converting a JPEG or HEIC photo to PNG produces a much larger file — typically 3–8× the JPEG size — because PNG is lossless and can't throw away the DCT compression artifacts already baked into the source. This is expected and correct behavior: PNG faithfully preserves whatever pixels are handed to it, including the JPEG artifacts. If you need smaller files, keep the photo as JPEG or convert to WebP/AVIF. Convert photos to PNG only when a specific downstream tool requires PNG input.
Transparency and alpha
PNG's alpha channel is bit-perfect. If your source is a WebP, AVIF, or HEIC with lossy alpha, the PNG output preserves whatever alpha data the source contained. If the source is transparent PNG or SVG, the alpha round-trips identically. Because PNG is lossless, you can convert PNG → any format → back to PNG and get identical pixels back (as long as the intermediate format supports alpha).