Eric J. Savitz 

$Snap Inc(SNAP.US)$ stock plunged in late trading Thursday after the social-networking firm posted disappointing revenue growth and guidance that fell shy of estimates. The parent of Snapchat said its advertising revenue was hurt more than expected by Apple's change in the rules surrounding advertising on mobile apps.

The miss weighed heavy on shares of other major social-media companies.

Snap stock was down 23% to $58.58. $Facebook(FB.US)$ and $Twitter(TWTR.US)$ were each down 5% on the news, while $Pinterest(PINS.US)$ and $Alphabet -CL A(GOOGL.US)$ were off 3% in late trading. Snap is the first of the companies to report September quarter results.

For the third quarter, Snap posted revenue of $1.067 billion, up 57% from a year ago, and below the company's guidance range of $1.07 billion to $1.085 billion. Adjusted Ebitda, or earnings before interest, taxes, depreciation, and amortization, was $174 million, well above its guidance range of $110 million to $120 million. On a non-GAAP basis, the company earned 17 cents a share in the quarter, beating the Street consensus of 8 cents a share. The company said it grew daily average users in the quarter by more than 20% to 306 million.

For the fourth quarter, Snap is projecting revenue of $1.165 billion to $1.205 billion, well shy of the Street consensus forecast of $1.36 billion. Snap is projecting adjusted Ebitda for the quarter of between $135 million and $175 million.

Snap blamed the miss in part on changes in $Apple(AAPL.US)$'s advertising tracking practices that make it harder to track consumer behavior across apps and websites.

Our advertising business was disrupted by changes to iOS ad tracking that were broadly rolled out by Apple in June and Jul.

While we anticipated some degree of business disruption, the new Apple-provided measurement solution did not scale as we had expected, making it more difficult for our advertising partners to measure and manage their ad campaigns for iOS."

-the company said in remarks prepared for the company's earnings conference call.

Snap said the issue "was compounded by the ongoing macroeconomic effects of the global pandemic, with our advertising partners facing a variety of supply-chain interruptions and labor shortages." The company said that factor reduced the "short-term appetite to generate additional customer demand through advertising at a time when their businesses are already supply-constrained."

Snap added that Apple's changes have "upended many of the industry norms and advertiser behaviors that were built on IDFA, Apple's unique device identifier for advertising, over the past decade, which now require a double opt-in by users in order to access directly."

The company noted that Apple has rolled out a proprietary solution known as SKAdNetwork, or SKAN, to allow app-based advertisers to continue measuring their advertising on iOS. But it says results have been disappointing.

The initial results we observed using SKAN were generally aligned with prior industry-standard solutions, and we were among the first platforms to lean into this solution and push for widespread industry adoption.

However, over time, we saw SKAN measurement results diverge meaningfully from the results we observed on other first- and third-party measurement solutions, making SKAN unreliable as a standalone measurement solution."

-the company said.

advertisers are no longer able to understand the impact of their unique campaigns based on things like the time between viewing an ad and taking an action or the time spent viewing an ad. Additionally, real-time campaign and creative management is hindered by extended reporting delays, and advertisers are unable to target advertising based on whether or not people have already installed their app."

-The company added