What is the PNG file format?
A .png file contains raster graphics compressed with a lossless method using the Deflate algorithm. The format supports an alpha channel for transparent pixels and stores up to 16 bits of color data per channel - enabling 48-bit color in RGB mode or 64-bit color in RGBA mode. Each .png file holds a single image; the format does not support animations. The APNG and MNG formats are used for animated images derived from the PNG design.
The file starts with a fixed 8-byte signature (89 50 4E 47 0D 0A 1A 0A). The non-ASCII first byte and the CR-LF sequence serve as intentional corruption checks that detect 7-bit transfers and incorrect line-ending conversions. After the signature, the file is organized into named blocks called chunks, each carrying a specific type of data. A .png file can store:
- RGB graphics
- RGBA (RGB with alpha transparency)
- ICC and ICM color profiles
- EXIF metadata
PNG was created in 1995-1996 as a patent-free alternative to .GIF and is endorsed by the W3C as a standard format for distributing images on the web. RFC 2083, which specifies the PNG format, was published in 1997; the ISO/IEC standard (ISO/IEC 15948) followed in 2004. PNG is widely used for sharing images and is suitable for print output, although it is not used in professional print workflows because it supports only the RGB color model and not CMYK. PNG files are supported by virtually all web browsers and image editing programs.
Security & safety
RISK: LOWA PNG is passive image data and safe to open in any modern, updated viewer. Two caveats: historically, malformed images have triggered bugs in image-decoding libraries, so keep your OS/viewer updated; and PNG metadata chunks (tEXt) can carry hidden text, while the format can be abused for steganography - but a PNG cannot execute on its own. A file named "photo.png" that is actually an EXE would still need to be run as a program; the PNG itself is not a malware vector.
Format details
in a nutshellPrograms that open PNG files
Windows4 apps
GIMP
Open-source Open for full editing; File → Export As to save PNG to other formats, with control over transparency. 
Photos / Paint (built-in)
Built-in Double-click to view in Photos; open in Paint to crop/resize and re-save. 
macOS2 apps
Preview (built-in)
Built-in Double-click to view; Tools → Adjust Size and File → Export to convert to JPG/other formats. 
Linux2 apps
Image viewer (Eye of GNOME / gThumb)
Open-source Double-click to view in the desktop's built-in image viewer.
Web browser
Free Drag the PNG into any browser tab to view it - PNG is natively supported everywhere. Technical details
deep spec| MIME type | image/png |
| File signature | 89 50 4E 47 0D 0A 1A 0A - fixed 8-byte magic at byte offset 0 |
| Compression algorithm | Deflate (RFC 1951) wrapped in zlib (RFC 1950) |
| Compression type | Lossless only - pixel values are preserved exactly |
| Supported color modes | Grayscale, Indexed (palette), RGB, RGBA |
| Bit depth | 1, 2, 4, 8, or 16 bits per channel depending on color mode |
| Maximum color depth | 64-bit RGBA (16 bpc × 4 channels); 48-bit for opaque RGB |
| Alpha transparency | Full alpha channel: 8-bit or 16-bit per pixel |
| Interlacing | Optional Adam7 two-dimensional interlace scheme for progressive display |
| Pre-compression filter | Five adaptive row filters: None, Sub, Up, Average, Paeth |
| File structure | Sequential named chunks: IHDR → one or more IDAT → IEND |
| Embedded metadata | ICC/ICM color profiles, EXIF, text annotations (tEXt, iTXt, zTXt chunks) |
| Color calibration | gAMA chunk stores display gamma; cHRM chunk stores chromaticity data |
| Palette support | Optional PLTE chunk - up to 256 indexed color entries |
| Animation | Not supported in the base format; APNG adds multi-frame capability |
| Print color model | RGB only - CMYK is not supported |
| Released | 1996 (created as a patent-free replacement for GIF) |
| Open standard | Yes · royalty-free |
| Specification | www.w3.org |
PNG conversions
Community Q&A
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