Tool to extract and understand the PNG format chunks. The PNG (Portable Network Graphics) image format consists of multiple pieces of data (header, image, meta information, or hidden content).
PNG Chunks - dCode
Tag(s) : Image Processing
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PNG Chunks
PNG Chunk Extraction
Answers to Questions (FAQ)
What is a PNG chunk? (Definition)
PNG (Portable Network Graphics) image files are composed of several parts, the chunks. Generally a file has a header, a content (iDAT) and an end. The PNG format also has its specification the ability to integrate a comment area chunk, compressed or not, a set of metadata usually unreadable without a dedicated software.
How to read a tEXt chunk?
The tEXt chunk is readable directly in the file (in a text editor or an hexadecimal editor), it starts with tEXt (74455874 in hexadecimal ascii), followed by a keyword/title, and a free comment area.
Example: TEXt => Keyword This is a PNG comment
How to read a zTXt chunk?
The zTXt chunk is similar to tEXt except that its content is compressed with DEFLATE. Find in the file zTXt (7a545874 in hexadecimal ascii), followed by a keyword/title (not compressed), and a binary area not readable directly (because compressed), that zone must be decompressed before being able to read the message.
How to read a iTXt chunk?
The iTXt chunk is similar to tEXt and zTXT but suitable for international use. It is marked with iTXt (69545874 in ascii hexadecimal), it is followed by a keyword/title (uncompressed) possibly translated, in this case, it is followed by a language code and the translated title, and finally, the content (which is compressed or not).
Source code
dCode retains ownership of the "PNG Chunks" source code. Any algorithm for the "PNG Chunks" algorithm, applet or snippet or script (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, breaker, translator), or any "PNG Chunks" functions (calculate, convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (Python, Java, PHP, C#, Javascript, Matlab, etc.) or any database download or API access for "PNG Chunks" or any other element are not public (except explicit open source licence). Same with the download for offline use on PC, mobile, tablet, iPhone or Android app.
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Cite dCode
The content of the page "PNG Chunks" and its results may be freely copied and reused, including for commercial purposes, provided that dCode.fr is cited as the source (Creative Commons CC-BY free distribution license).
Exporting the results is free and can be done simply by clicking on the export icons ⤓ (.csv or .txt format) or ⧉ (copy and paste).
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In a scientific article or book, the recommended bibliographic citation is: PNG Chunks on dCode.fr [online website], retrieved on 2025-07-14,
