Remove PNG metadata: what the chunks hold and what the cleaner dropped
Remove PNG metadata: what the chunks hold and what the cleaner dropped?
PNG metadata sits in optional chunks next to the pixel data. This page lists those chunks, shows a recorded before and after run from the Metadata Cleaner, and says which cases were not measured. A PNG is a stream of chunks.
C2PA: Coalition for Content Provenance and Authenticity; C2PA specification 2.4
Last updated
PNG metadata sits in optional chunks next to the pixel data. This page lists those chunks, shows a recorded before and after run from the Metadata Cleaner, and says which cases were not measured.
Evidence checked 2026-10-18
What a PNG can carry
A PNG is a stream of chunks. The decoder needs IHDR, IDAT and IEND. Everything else is ancillary, and each ancillary chunk is a place where text, a time stamp, a color tag, or a provenance manifest can sit.
| Chunk | Holds | Why it matters for privacy |
|---|---|---|
| tEXt, zTXt, iTXt | A keyword and text, uncompressed, compressed, or UTF-8 | Author, Description, Software, Source and Comment are predefined keywords. Any other keyword is allowed. |
| iTXt “XML:com.adobe.xmp” | An XMP packet | Editing history, creator tool, and rights fields written by Adobe and other editors. |
| eXIf | An EXIF block | Camera, time and GPS tags, as in a JPEG. Added in the PNG third edition. |
| tIME | Last-modified time, UTC | A date that survives a copy. |
| caBX | C2PA manifest store | Content Credentials. See what C2PA is. |
| iCCP, sRGB, gAMA, cHRM | Color description | Not personal data, but it changes how colors render. |
Source: W3C PNG specification, third edition. Tag-level detail is in the ExifTool PNG tag list.
What the Metadata Cleaner does to a PNG
The homepage cleaner reads the file with createImageBitmap, draws it onto a canvas, and calls toBlob with type image/png. Nothing in that path copies ancillary chunks, so the exported file has the pixels and whatever the browser's PNG encoder writes. The file never leaves the tab.
Browser run on 2026-10-02 in Chrome/154.0.8037.92, using the live Metadata Cleaner on the homepage. The block table below was computed afterwards by this site's own parser on the input and output files, which are published with the metadata removal report.
| Block | Before (bytes) | After (bytes) | Result |
|---|---|---|---|
| Pixel density (pHYs) | 21 | — | Removed |
| Text chunk tEXt “Description” | 55 | — | Removed |
Fields the viewer could read before and not after: Description = Synthetic alpha channel fixture. Fields still readable after: Width = 32; Height = 24 (image size only). The browser check recorded: The description text is absent from the cleaned png. Alpha is still present. Dimensions are 32x24.
The pHYs chunk is not personal data. It stored pixel density, and the export dropped it, so a print size taken from the old file's DPI will not carry over.
What was not measured
The recorded run used one 32×24 synthetic PNG with one text chunk and an alpha channel. It had no eXIf chunk, no XMP iTXt, no caBX, no iCCP, and no animation. Those cases are not verified here.
An animated PNG (APNG) exported through a canvas keeps only the first frame in most browsers. That is a behavior of canvas export and was not tested on this page, so check an animated file before you replace the original.
Pixels are untouched by design. A name, a face, or a date drawn into the picture is still there. The removal benchmark records a burned-in date stamp as a partial result for the same reason.
Check your own PNG in ten seconds
Open the Image Metadata Viewer on the original and note the text chunks. Clean a copy with the Metadata Cleaner. Then drop both files into Verify metadata removed. It lists every chunk in each file, marks what was removed or kept, and prints both SHA-256 hashes, all inside the page.
Related reading: what image metadata is, XMP metadata, PNG metadata lab, image format labs.
FAQ
Does removing PNG metadata change the pixels?
The cleaner decodes the PNG into a canvas and exports a new PNG with no quality setting, so the pixel values are written back as decoded. In the recorded run the 32×24 alpha fixture kept its size and its alpha channel.
Which PNG chunks did the recorded run drop?
The tEXt “Description” chunk (55 bytes) and the pHYs pixel-density chunk. The file went from 179 to 127 bytes.
Is a PNG with a C2PA caBX chunk covered?
Not measured. The recorded run had no caBX chunk. Re-encoding through a canvas does not write one, but this page does not claim a measured result for it.
Do AI image tools put prompts in PNG text chunks?
A PNG text chunk can hold any keyword and text, so a tool is free to store settings there. The PNG specification only predefines keywords such as Title, Author, Description, Copyright, Creation Time, Software and Source. Check your own file in the viewer to see what it carries.
More tools
Metadata Cleaner · Verify metadata removed · Image Metadata Viewer · Removal benchmark