It wasn’t a good day for companies that rely on advertising revenue. The technology industry lost billions this morning — especially those focused more heavily on advertising.

Google’s parent company Alphabet, Facebook, Twitter, Pinterest, and others fell Friday after Snap reported disappointing quarterly earnings — warning that executives predict a delay in ad spend during the holiday season, resulting from Apple iOS privacy changes, bottleneck in the supply chain, and U.S. labor shortage.

Snap saw the biggest decline today — 25.30%, as of writing of this article at noon on Friday.

Some investors are now calling Snap a bellwether for the market.  

“Throughout this year, we highlighted Apple as the clear winner from IDFA changes, with Amazon and Google as modest beneficiaries, and Facebook, Snap and Zynga as likely losers,” wrote Colin Sebastian, senior research analyst at Baird Capital, in a research note. “As with Snap, management teams will also likely guide cautiously due to fears over supply chain headwinds.”

Google’s parent company Alphabet plummeted 3.55%, while Facebook fell 5.89%, Twitter fell 4.33%, Pinterest fell 4.21%, Amazon fell 2.69, Microsoft fell 0.74%, and Apple fell 0.29%.

Smaller companies in the ad space also experienced declines. Magnite (formally Rubicon Project) fell 11.08%, while PubMatic fell 8.09%, Criteo fell 8.09%, The Trade Desk fell 7.21%, and Integral Ad Science Holding fell 3.11%.

Tech stock also declined in value. Intel fell 10.99%. Trip Chowdhry, managing director of equity research at Global Equities Research, advised investors earlier in the day to “buy on weakness,” and that the company has “solid, long-term fundamentals.”

Advertising agencies also rode the slide. The stock price for WPP PLC fell 2.09%, Omnicom Group fell 1.91%, and Interpublic Group of Companies fell 0.86%.