Online ad sellers added over $100 billion stock market value late on Tuesday after upbeat quarterly results from Alphabet, Reddit and Snap lifted investor optimism ahead of reports from Amazon and Meta Platforms.

Alphabet's stock rallied 4 percent in extended trade after it topped quarterly revenue expectations, helped by steady growth in its digital advertising business and an AI-driven jump in demand for its cloud services.

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Meta Platforms and Amazon, both rivals of Alphabet in advertising and AI, each gained over 1 percent following the Google owner's report. Meta provides its results on Wednesday and Amazon reports on Thursday.

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Snap, a smaller player in online ads, beat Wall Street expectations for both quarterly revenue and user growth, sending its stock 7 percent higher. Struggling with competition from TikTok and other heavyweight rivals, Snap's stock has tumbled over 30 percent in 2024.

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Reddit surged 20 percent in extended trade after forecasting quarterly revenue above Wall Street estimates, helped by its AI content licensing deals. That stoked optimism that more advertisers are turning to the platform following its Wall Street debut in March.