Remove Metadata & Text Chunks From PNG Files

PNG Chunk Anatomy

Understanding the PNG Chunk Structure

The Portable Network Graphics (PNG) specification organizes file data into discrete, self-contained segments called chunks. Every chunk consists of a 4-byte length field, a 4-byte ASCII chunk type, the chunk data payload, and a 4-byte Cyclic Redundancy Check (CRC-32) checksum.

The PNG standard divides chunks into two fundamental categories:

• Critical Chunks (Required): These chunks are mandatory for decoding the visual image:
  • IHDR: Image header containing width, height, bit depth, color type, and compression method.
  • PLTE: Color palette table (for indexed-color images).
  • IDAT: The zlib-deflated image pixel scanlines.
  • IEND: Marks the official end of the PNG datastream.
• Ancillary Chunks (Optional Metadata): These chunks contain non-visual data that can be safely discarded without affecting image rendering:
  • eXIf: Stores standard raw EXIF metadata (camera data, GPS coordinates, timestamps).
  • tEXt: Key-value text strings (such as Software, Author, Copyright, Creation Time).
  • zTXt: Deflate-compressed text strings (often used for large Photoshop edit histories).
  • iTXt: Internationalized UTF-8 text strings (used by XMP packets and modern design suites).
  • tIME: The exact UTC modification timestamp of the file.

Web Asset Optimization: Stripping Dead Weight

Frontend engineers and UI designers frequently export hundreds of icon assets, UI buttons, and transparent graphics for production web applications. When exported directly from suites like Figma, Adobe Illustrator, or Photoshop, each PNG carries significant metadata overhead:

Stripping ancillary chunks during build or pre-deployment optimization provides instantaneous performance gains without altering a single rendered pixel or disrupting alpha-channel transparency.

Security & Intelligence

OSINT & Information Leakage in PNG Screenshots

PNG is the standard file format for screenshots captured on macOS, Windows (Snipping Tool), iOS, and Android. While screenshots rarely contain hardware camera lens data, they routinely leak operational and identity intelligence:

• Mac Screenshot Timestamps: macOS stores detailed capture timestamps and window identifiers inside iTXt chunks.
• Internal Software Versions: Graphics exported from internal design builds or beta tools record exact build hashes and internal developer usernames.
• Color Profile Information: Uncompressed iCCP chunks embed proprietary corporate color profiles that bloat files without providing visual benefit on standard sRGB web displays.

Binary Chunk Slicing vs. Image Re-compression

Many online PNG compressors run images through lossy color quantization (reducing 24-bit Truecolor to 8-bit indexed palettes), which causes banding across gradients and ruins transparent drop-shadows.

ManageMetadata Guarantee: Our client-side PNG sanitizer performs pure binary chunk filtering. It retains your 24-bit/32-bit Truecolor RGBA channels and Deflate IDAT streams untouched, slicing only the ancillary metadata chunks from the byte array.