GPT Light is explicitly designed to be lightweight and less feature rich than the standard GPT tag. The set of available features and restrictions should be considered when deciding which tag to use. These restrictions are subject to change.
GPT Light is currently only supported as a passback tag.
Cross Domain Restrictions
GPT Light renders ads in a cross-domain iframe. This means that communication between the creative and publisher pages is more complex, requiring use of postMessage.
All requests from GPT Light are made over HTTPS.
GPT Light does not support any notion of Sync mode.
Does not support SRA
GPT Light requests each ad individually.
No Publisher Console
GPT Light does not support the Publisher Console.
No Multi-Size requests
GPT Light does not support multi-size requests.
Max Request Size
GPT Light currently has a maximum ad request URL size of 4k characters and truncates rather than falling back to POST if exceeded.