What is a PNG file?
PNG is a lossless raster image format created in 1996 as a patent-free replacement for GIF. Every pixel is stored exactly, so screenshots, diagrams, logos and text stay crisp no matter how many times the file is saved. It supports 24-bit colour plus an 8-bit alpha channel, which gives smooth, partial transparency that GIF cannot offer.
Compression is based on the same algorithm as ZIP, which works well on flat colours and repeated patterns but poorly on photographs: a photo saved as PNG is often several times larger than the same image as JPG. PNG can store metadata and a colour profile, but not animation; APNG, a separate extension, covers that.
When PNG is the right choice
Strengths
- Lossless: pixels are preserved exactly through every save
- Real alpha transparency for logos, icons and overlays
- Sharp text and lines in screenshots and diagrams
Limitations
- Photographs become large compared with JPG or WebP
- No animation in the base format
- No native support for layers or vector shapes
How to open a PNG file
Every browser, operating system and image editor opens PNG. To check the resolution stored for printing, use the DPI checker; to change it without resampling, the DPI converter.
How to convert a PNG file
PNG to JPG shrinks photos that do not need transparency, PNG to WebP keeps transparency in a smaller file for the web, PNG to PDF makes a document from screenshots, and PNG to ICO produces a Windows icon. PNG to SVG traces simple graphics into vector paths.