What is the exact 8-byte signature that identifies a PNG file?

• A. 89 50 4E 47 0D 0A 1A 0A
• B. FF D8 FF E0 00 10 00 00
• C. 25 50 44 46 2D 31 2E 34
• D. 50 4B 03 04 14 00 06 00

Answer: (A)

The 8-byte sequence used to identify a PNG file is the exact header at the very start: 89 50 4E 47 0D 0A 1A 0A. The first byte, 0x89, is a non-ASCII value chosen to help detect corrupted transfers of binary data. The next three bytes spell PNG in ASCII (0x50, 0x4E, 0x47). The final quartet (0x0D 0x0A 0x1A 0x0A) enforces proper line endings and adds a control character, aiding in detecting truncation or tampering. This 8-byte signature is what a parser checks first to confirm a PNG file. Other formats have different signatures—for example, JPEG typically starts with 0xFF 0xD8, PDF with "%PDF" (0x25 0x50 0x44 0x46), and ZIP with "PK" (0x50 0x4B 0x03 0x04)—so they don’t match the PNG header.