PNG Chunk Extractor

PNG files are built from chunks — discrete data blocks that each serve a specific purpose. Critical chunks (IHDR, PLTE, IDAT, IEND) contain the actual image data. Ancillary chunks can carry hidden metadata such as text comments, EXIF data, ICC color profiles, timestamps, and even AI generation prompts. Our tool extracts and decodes all these chunks so you can inspect what's really inside a PNG file.

AI image generators like Stable Diffusion, Midjourney, and ComfyUI often embed generation parameters inside PNG metadata. Upload your image here, then look for tEXt or iTXt chunks with keywords like parameters, prompt, negative_prompt, or Comment. Our tool highlights text chunks in green for easy spotting. The full prompt, seed, sampler, CFG scale, and step count are typically stored as a JSON or plain text string.

No. All processing happens entirely inside your browser using JavaScript. Your file is never transmitted to any server. This makes our tool safe for sensitive images and private metadata. The file is read locally via the FileReader API, parsed in memory, and discarded when you close the page or upload a new file.

All three store textual metadata, but they differ in encoding and compression:
tEXt — Uncompressed, Latin-1 encoded. Most common for AI prompts and simple comments.
zTXt — Compressed with zlib/deflate, Latin-1 encoded. Saves space for larger text payloads.
iTXt — UTF-8 encoded, optionally compressed. Supports international characters and language tagging. Ideal for multilingual metadata.

Yes. Many image editors and command-line tools (like pngcrush, optipng, or exiftool) can strip ancillary chunks without affecting the visible image. On the web, re-saving a PNG through certain services may also discard metadata. Use our tool to verify what metadata remains before and after stripping.

CRC (Cyclic Redundancy Check) is a 4-byte checksum at the end of every PNG chunk. It verifies data integrity. Our tool recalculates the CRC and compares it to the stored value. A ✓ OK means the chunk is intact; a ✗ FAIL indicates possible corruption or tampering.

The most common chunks carrying hidden data are tEXt, iTXt, zTXt (text metadata), eXIf (EXIF camera/settings data), iCCP (ICC color profile), and tIME (last modification timestamp). Less common but still possible: custom private chunks that software vendors define for their own purposes.