Google has had a pretty rough relationships with photographers.
Today it announced a small measure that should go some way toward making image rights holders a little happier.
Google has worked with IPTC (International Press Telecommunications Council) to add Creator and Credit meta-data whenever found to images on Google Images
IPTC is a standards consortium that constitutes some of the world’s biggest news agencies, including the BBC, Associated Press (AP), Agence France-Presse (AFP), and the New York Times.

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An images copyright tag can be modified in Lightroom via Library > Metadata > Copyright, Copyright Status, Creator.

Copyright data can also be added automatically to images on import via the ‘Apply During Import’ meta-data panel.
Lightroom will always write copyright meta-data on image export.

Photoshop allows modification of meta-data via File > File Info


If you an unafraid of using command line the excellent EXIFTOOL allows you to modify a range of metadata.
If you wish to write copyright to every image in a directly you can use a wildcard *
exiftool -overwrite_original -copyright="2018 Copyright Holders Name" -creator="Creator Name" filename.jpgexiftool -overwrite_original -copyright="2018 Copyright Holders Name" -creator="Creator Name" *.jpgIncluding the -overwrite_original tag will overwrite the existing file.
Removing the -overwrite_original tag will create a copy of your original file with the filename .jpg_original.

You can use exiftool -a -S -copyright * to view the copyright data attached to every file in a directory.
You can use exiftool -a -S -copyright filename.jpg to display a single files copyright data.
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For more information read IPTC standards guidelines