The short answer
- PNG is a losslessly compressed raster image format that stores static or frame-by-frame animated images, with optional alpha transparency and sample depths from 1 to 16 bits.
- Open a PNG in a current web browser, image viewer, or image-editing application. On Windows, double-click it or choose an installed image app with Open with. On macOS, open it in an installed image viewer or editor. On a phone, select the file from the device’s file or image interface and choose a compatible viewer. If it fails, verify the eight-byte signature and required IHDR, IDAT, and IEND chunk sequence; a matching extension alone does not prove that the stream is valid.
- Treat an unfamiliar PNG as untrusted input. Standard registered chunks generally affect image presentation rather than carry executable data, but malformed, future, or unregistered chunks cannot be assumed harmless. Parsers must handle chunk lengths that can reach 2^31−1 bytes and filter control characters in text chunks. Transparent pixels may retain recoverable sensitive imagery, and an eXIf chunk may contain metadata such as GPS coordinates. A valid signature or CRC detects some structural or accidental damage; it does not establish that the file is safe or trustworthy.
PNG File: What It Is, How to Open It, and How to Convert It
Portable Network Graphics stores indexed-color, grayscale, truecolor, grayscale-with-alpha, or truecolor-with-alpha images. A PNG stream begins with the eight-byte signature 89 50 4E 47 0D 0A 1A 0A, then uses chunks: IHDR comes first, one or more IDAT chunks carry image data, and IEND closes the stream. Each chunk includes a length, four-byte type, optional data, and a CRC. Its registered media type is image/png.
PNG uses reversible filtering and lossless DEFLATE compression, so compliant decoding can reconstruct the original reference image data bit for bit. A conversion or edit can remain lossless when all required image information is preserved. Reducing bit depth, changing color representation, quantizing colors, discarding alpha, or converting to a format without equivalent transparency can prevent exact reconstruction. In particular, check transparency before converting PNG to JPG.
How to open it
Open a PNG in a current web browser, image viewer, or image-editing application. On Windows, double-click it or choose an installed image app with Open with. On macOS, open it in an installed image viewer or editor. On a phone, select the file from the device’s file or image interface and choose a compatible viewer. If it fails, verify the eight-byte signature and required IHDR, IDAT, and IEND chunk sequence; a matching extension alone does not prove that the stream is valid.
Open a PNG in a current web browser, image viewer, or image-editing application. On Windows, double-click it or choose an installed image app with Open with. On macOS, open it in an installed image viewer or editor. On a phone, select the file from the device’s file or image interface and choose a compatible viewer. If it fails, verify the eight-byte signature and required IHDR, IDAT, and IEND chunk sequence; a matching extension alone does not prove that the stream is valid.
PNG uses reversible filtering and lossless DEFLATE compression, so compliant decoding can reconstruct the original reference image data bit for bit. A conversion or edit can remain lossless when all required image information is preserved. Reducing bit depth, changing color representation, quantizing colors, discarding alpha, or converting to a format without equivalent transparency can prevent exact reconstruction. In particular, check transparency before converting PNG to JPG.
File safety
Treat an unfamiliar PNG as untrusted input. Standard registered chunks generally affect image presentation rather than carry executable data, but malformed, future, or unregistered chunks cannot be assumed harmless. Parsers must handle chunk lengths that can reach 2^31−1 bytes and filter control characters in text chunks. Transparent pixels may retain recoverable sensitive imagery, and an eXIf chunk may contain metadata such as GPS coordinates. A valid signature or CRC detects some structural or accidental damage; it does not establish that the file is safe or trustworthy.
An unknown sender, a name ending in two extensions, or contents that do not match the extension — check before you open it.
Converting it
PNG uses reversible filtering and lossless DEFLATE compression, so compliant decoding can reconstruct the original reference image data bit for bit. A conversion or edit can remain lossless when all required image information is preserved. Reducing bit depth, changing color representation, quantizing colors, discarding alpha, or converting to a format without equivalent transparency can prevent exact reconstruction. In particular, check transparency before converting PNG to JPG.
Convert a copy, never the original, then compare quality, metadata, and layout against what you started with.
Common questions
What is a PNG file and what is it used for?
A PNG file is a losslessly compressed raster image that can store static or frame-by-frame animated imagery. It supports indexed color, grayscale, truecolor, optional alpha transparency, and sample depths from 1 to 16 bits.
How do I open a PNG file in a web browser?
Choose the PNG with the browser’s file-opening command or open it from the device into a current browser. Browsers widely support PNG, but a file that does not decode may be damaged or may not actually contain a valid PNG stream.
How do I open a PNG file on Windows 11?
Double-click the PNG or use Open with and select an installed browser, image viewer, or image editor. If no application accepts it, check that its content starts with the PNG signature rather than relying only on the .png extension.
How do I open a PNG file on a Mac?
Open the PNG with an installed image viewer, browser, or image-editing application. If macOS cannot decode it, verify the file’s signature and required chunk structure before changing applications.
How do I open a PNG file on a phone?
Select the PNG in the phone’s file or image interface and choose a compatible image viewer or browser. Very large or malformed chunks can still exceed an individual application’s safe processing limits.
Why is my PNG file not opening or reported as damaged?
The stream may have a wrong signature, a missing or misplaced IHDR, IDAT, or IEND chunk, damaged chunk data, or a CRC mismatch. CRC can reveal accidental damage to a chunk’s type and data, although it does not repair the file.
What is the difference between PNG and JPG for transparency?
PNG can preserve an alpha channel, while converting to a format without equivalent transparency requires the alpha information to be discarded or replaced. Choose PNG when that transparency must remain exactly represented.
How do I convert a PNG file to JPG, and will transparency be lost?
Open the PNG in a compatible image editor or converter and export to JPG. Because equivalent alpha transparency is not retained, inspect transparent areas and choose their replacement appearance before conversion; the result may not permit exact reconstruction of the PNG.
Is a PNG file from an email safe to open?
The .png extension, signature, and valid CRC are not safety guarantees. Use a maintained decoder and treat malformed, future, or unregistered chunks as untrusted; text controls, oversized chunks, recoverable hidden pixels, and eXIf metadata can create security or privacy concerns.
What are the official PNG MIME type and hexadecimal file signature?
The registered media type is image/png. A PNG data stream starts with the eight bytes 89 50 4E 47 0D 0A 1A 0A, but those bytes alone do not prove that every required chunk is valid.
Related formats
Sources
Portable Network Graphics (PNG) Specification (Third Edition) · W3C Recommendation and official PNG specification
IANA Media Type Registration: image/png · Internet Assigned Numbers Authority (IANA)
Portable Network Graphics — Sustainability of Digital Formats · Library of Congress