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No, you don't need to get a visa. 24-Hour Direct Transit is available to most countries: contrary to the 72- and 144-hour transit visas, which have a set list of eligible countries, China lists countries that are not eligible for 24-hour direct transit. Fortunately for you, India is not in that list. So your layover of 15 hours can be done without a visa. You will be able, if you want, to go check in in a nearby hotel and take a good rest before going back to the airport.