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How can I edit metadata of a PNG file?

Is there some free software I can use?

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  • \$\begingroup\$ Surprisingly, this seems like a hard thing to do. While a quick search turned up a few non-free programs that claimed to be able to edit PNG metadata, the only free options I found were for command line programs; not the easiest things to use. blog.client9.com/2007/08/… \$\endgroup\$
    – Sean
    Oct 2, 2010 at 21:23
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    \$\begingroup\$ What operating system(s) are you interested in doing this on? \$\endgroup\$
    – Rowland Shaw
    Oct 3, 2010 at 9:24
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    \$\begingroup\$ Just a note: meta-data do not necessarily follow the file if manipulated in other programs. The reason for this is that programs are free to support or ignore any additional chunks in the file besides the image descriptor and data itself. This means the program can "forget" the unsupported (by the program) chunks when re-saving the file back to disk. Properly written programs will "remember" those chunks and save them along. I just mention this as someone said that data doesn't always stick - this is the main reason in addition to software that removes these on purpose to reduce file-size. \$\endgroup\$
    – epistemex
    Dec 14, 2012 at 19:18

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From the Wikipedia page for 'pngcrush',

The main purpose of pngcrush is to reduce the size of the PNG IDAT datastream by trying various combinations of compression methods and delta filters. However, pngcrush can also be used for various manipulations of PNG images, such as changing the bit depth, removing unwanted ancillary chunks, or adding certain chunks including gAMA, tRNS, iCCP, and textual chunks.

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TweakPNG is a free software that can edit PNG metadata (Windows only).

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  • \$\begingroup\$ It's a easy GUI Program. Good. No need to learn how to use a command line tool. \$\endgroup\$
    – rint
    Feb 16, 2023 at 16:38
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ExifTool can edit PNG metadata. You can find the list of the supported tags here.

Exiftool is a free command line tool, but there are GUI tools (listed on the ExifTool website) using the ExifTool engine.

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The new-ish default Windows 10 photo viewer ("Photos") lets you edit PNG metadata now:

  • "..." menu (top right)
  • "File info"
  • Can change the name or Date Taken fields there

If you only care about date and not time, you can change other date properties directly in Explorer (via preview panel) or from the right-click Properties window

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If metadata is added to PNG files, such as keywords, it doesn't "stick" permanently. I found the only safe way was to use Bridge > Photoshop > Image processor and batch change the PNG to a JPEG, PSD, or TIFF file. I used tiff LZW to save space and even then it is a larger file than the png. I needed this to be able to add keywords and descriptions to pngs in scrapbook kits.

This was not my idea completely. I was changing the file extension in a more round about way and found this presented by a scrapbooker whose name and site I forget. I think her first name was Kayla.

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  • \$\begingroup\$ This? digiscrap101.com/2011/03/… \$\endgroup\$
    – mattdm
    Dec 30, 2011 at 1:24
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    \$\begingroup\$ I may be misreading it, but it sounds to me that @liz is not adding metadata to the PNG files at all. Rather converting to some other format that handles meta data better, and using that. Is this what you are really doing? \$\endgroup\$
    – Pat Farrell
    Dec 13, 2012 at 4:01
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For the MAC OSX, there is a freeware called 'PNGCommentator'.
Have not seen it on other platforms.

PNG metadata can now be added and edited at the click of a mouse. Version 1.2 adds support for batch processing and customisable presets, allowing for much faster workflows. Text macros extend this even further, allowing the software to automatically insert data such as the date or filename.

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MetadataTouch can edit PNG metadata, but it is not free.

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