PNG is known for lossless compression, transparency, screenshots, logos, diagrams, and web graphics. It is also frequently described as if it were a metadata-free alternative to JPEG.
That description is inaccurate.
PNG is a chunk-based format, and its specification defines several places where descriptive or technical information can live. A PNG can contain text, Exif data, timestamps, color-management information, and other ancillary chunks. Applications can also use established conventions for metadata such as XMP.
If you care about privacy, inspect the actual PNG rather than assuming the extension makes it clean.
PNG is built from chunks
The W3C PNG Third Edition specification defines PNG as a sequence of typed chunks. Some chunks are critical to decoding the image. Others are ancillary and carry optional information.
That architecture matters for metadata cleaning.
A safe cleaner should understand which chunks are image-critical and which are removable metadata. It should not simply delete everything it does not recognize.
Text metadata: tEXt, iTXt and zTXt
PNG has three well-known textual metadata chunk types:
tEXtfor Latin-1 text;zTXtfor compressed Latin-1 text;iTXtfor international text using UTF-8, with optional compression.
The PNG specification says these chunks can hold text strings associated with the image, such as descriptions or copyright notices.
A keyword identifies what the text represents.
Examples could include:
- Title
- Description
- Author
- Copyright
- Comment
- Software
- custom application keys
The standard permits multiple text chunks, including more than one with the same keyword.
Why text chunks matter for privacy
A screenshot or exported graphic can look anonymous while a text chunk contains a username, software identifier, workflow note, prompt-like information, or other application-generated data.
The metadata itself is not guaranteed to be private. A copyright notice may be intentional. The point is that PNG text should be inspected.
EXIF in PNG: the eXIf chunk
Current PNG supports Exif explicitly.
The PNG Third Edition specification defines the eXIf chunk for storing an Exif profile.
This corrects a common outdated claim that PNG simply “does not support EXIF.”
An eXIf chunk can therefore carry familiar Exif concepts such as camera fields, timestamps, and GPS information, depending on what software wrote the file.
The specification also warns that Exif may describe the original image data and may become stale if the PNG is edited later.
That is an important forensic limitation. A valid Exif field can be historical rather than current.
Can PNG contain GPS coordinates?
Yes, if GPS data exists inside an Exif profile stored in the eXIf chunk.
Location could also appear in textual metadata or application-specific XMP-like data.
A privacy scanner should therefore check both structured Exif and textual fields instead of looking only for a GPS keyword.
XMP in PNG
XMP is an extensible metadata framework. Adobe documents XMP as a way to embed structured metadata in common media formats.
PNG software has long used an iTXt convention for XMP packets, commonly associated with the XML:com.adobe.xmp keyword. Tool support can vary, which is why a PNG metadata viewer should explicitly state whether it recognizes XMP conventions in text chunks.
An XMP packet can contain creator information, descriptions, rights, software fields, editing details, ratings, or custom namespaces.
tIME: modification time
PNG also defines a tIME chunk representing the time of the last image modification rather than the original capture time.
That distinction matters.
A user might see a PNG date and assume it is equivalent to a camera's DateTimeOriginal. It is not.
Metadata viewers should label time fields by their actual meaning rather than grouping every date under “Photo taken.”
Color metadata in PNG
PNG can contain color-related information such as ICC profiles and standardized color-space signaling.
These fields are generally about correct rendering, not personal privacy.
A metadata remover aimed at privacy should preserve color information by default unless the user intentionally chooses a more aggressive cleanup.
Deleting color metadata can change the way an image looks across browsers, editors, or displays even though the pixel values are the same.
Other ancillary chunks
PNG supports additional ancillary chunks that describe properties such as physical pixel dimensions, significant bits, background color, palette information, and more.
Not every ancillary chunk should be called “personal metadata.”
A responsible cleaner needs categories:
- privacy/descriptive metadata;
- color/rendering metadata;
- image-control information;
- unknown ancillary data.
That prevents a “remove everything” button from accidentally producing a file that renders differently or loses useful semantics.
What about PNG screenshots?
Screenshots are often PNG, especially on desktop systems.
A screenshot usually creates a new image and does not copy the original source photo's EXIF wholesale. But the screenshot file can contain its own software, date, text, color, or file-level information.
The correct rule is not “screenshots have no metadata.” The correct rule is “screenshots are new files, so inspect the new file.”
Can AI generators store prompts in PNG metadata?
Some local and creative AI workflows have used PNG textual metadata for generation parameters, prompts, seeds, model information, or workflow data.
There is no universal PNG prompt standard, and not every AI-generated PNG contains such fields.
A metadata viewer should display the actual keyword and value when it recognizes the structure. It should not label every text chunk as an AI prompt.
Likewise, absence of prompt metadata does not prove the image was not generated by AI.
Can C2PA exist with PNG?
The Content Authenticity Initiative's public verifier lists PNG among supported formats for Content Credentials inspection.
C2PA is a provenance system and should be reported separately from ordinary PNG text or Exif metadata.
If a cleaner removes or invalidates a credential while rewriting the PNG, it should warn the user.
How to remove PNG metadata safely
A format-aware PNG cleaner should:
- parse the chunk stream;
- identify
tEXt,iTXt,zTXt,eXIf, recognized XMP and other supported metadata; - distinguish color and rendering chunks from privacy metadata;
- remove only selected chunks;
- recalculate the required chunk checksums;
- preserve the critical image data;
- validate the output;
- re-scan the new file.
This approach can preserve the decoded pixels exactly because there is no need to re-encode the image data merely to delete ancillary metadata.
Should you remove all PNG text?
Not automatically.
A graphic may intentionally include:
- author attribution;
- copyright;
- public description;
- accessibility-related information;
- workflow fields needed downstream.
For a casual public derivative, removing unnecessary comments and application details may make sense. For a professional asset, selective cleaning is better.
Conclusion
PNG is not metadata-free. It can carry textual information, Exif, timestamps, color profiles, XMP conventions, and other ancillary data.
The format's chunk structure actually makes careful metadata cleaning possible: remove the privacy-related chunks you do not need while preserving critical image data and useful color information.
The key is to treat PNG as PNG, not as “JPEG without EXIF.”
Helpful answers
Frequently Asked Questions
Can a PNG have an embedded camera thumbnail?
If the PNG contains an Exif profile, that Exif data may include thumbnail structures depending on how it was created. A scanner should report what it finds rather than assuming PNG never has previews.
What is the difference between `tEXt` and `iTXt`?
tEXt stores Latin-1 text, while iTXt supports UTF-8 international text and additional language-related fields. Both can carry descriptive information associated with the image.
Does removing PNG metadata reduce transparency quality?
No, not if the cleaner edits only metadata chunks and preserves the image data and alpha information. Transparency problems indicate the tool did more than metadata cleanup.
Can a PNG's `tIME` show when a screenshot was taken?
It can describe the last modification time if the software writes the chunk, but not every screenshot includes it. File-system timestamps are separate and may also differ after copying or downloading.