PNG Chunk Inspector
A PNG file is a magic 8-byte signature followed by a sequence of chunks. Each chunk has a length, a 4-letter type code, payload bytes, and a 32-bit CRC. The case of each letter in the type encodes flags — uppercase first letter is `critical` (the decoder must handle it), lowercase is `ancillary`. This inspector parses the whole file in the browser, lists every chunk with its meta, surfaces the IHDR header (dimensions, color type, bit depth), and decodes any `tEXt` / `iTXt` metadata blocks — common places editors hide signatures, copyrights, or camera notes.
How to use
- Drop a `.png` file. The IHDR summary and chunk list appear immediately.
- The chunk table shows the 4-letter type, payload length, and the four type-bit flags.
- Any `tEXt` / `iTXt` metadata is decoded at the bottom — useful for spotting embedded copyright tags or editor signatures.
Frequently asked questions
- What are critical vs ancillary chunks?
- Critical chunks (IHDR, PLTE, IDAT, IEND — first letter uppercase) must be understood by a decoder for the image to render. Ancillary chunks (lowercase first letter, e.g. `tEXt`, `pHYs`, `tIME`) carry metadata that decoders can safely ignore.
- Where do `tEXt` keys come from?
- Standard registered keys are `Title`, `Author`, `Description`, `Copyright`, `Creation Time`, `Software`, `Disclaimer`, `Warning`, `Source`, `Comment`. Editors usually write `Software` (the name of the editor) and sometimes private custom keys.
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