Key Highlights

  • CoStar Group (NASDAQ:CSGP) fell 14% to 15% on October 28, 2026, according to published market data, even though third-quarter revenue reached USD 952 million, up 14% from a year earlier.
  • Reversing the growth rate gives prior-year revenue of about USD 835 million, simple arithmetic on two published numbers: USD 952 million divided by 1.14. The figure is derived and not reported.
  • Recaps conflict on guidance: one says full-year guidance was raised, another says revenue guidance was weak, so the true cause of the selloff is not verified.
  • A double-digit fall on a revenue beat-style print suggests the market focused on guidance, margins or expectations, but none of those drivers was confirmed in the reviewed material.

Growth Met, Shares Fell

CoStar Group (NASDAQ:CSGP) reported third-quarter revenue of USD 952 million, up 14%, according to the company release, and its shares fell 14% to 15% on October 28, 2026. Reversing the growth rate, the prior-year quarter was about USD 835 million, simple arithmetic on published numbers. The material reviewed did not give earnings per share, margins, cash flow or consensus estimates, so it is unclear whether the quarter beat or missed expectations. The mismatch between solid growth and a steep fall usually means something other than headline revenue disappointed, which makes the reaction harder to explain from the numbers alone. Without consensus numbers, it is not possible to say whether the market saw this as a shortfall.

The Guidance Conflict

One recap says CoStar Group (NASDAQ:CSGP) raised full-year guidance, while another points to weak revenue guidance. Both cannot be fully right, and the file reviewed marks the cause as not verified. Guidance is management's forecast for future results, and markets often react more to a change in that forecast than to the quarter just reported. A raised full-year figure could still imply a slower fourth quarter, which is one way both descriptions might coexist, though that is conjecture. The only reliable way to settle it is to read the company release and guidance table directly, which was not available in the material reviewed. Readers should therefore avoid relying on either description until the primary document is checked.

Risks and What to Watch

Until the guidance is confirmed, any narrative is provisional. The wider backdrop was weak: Nasdaq-100 futures were down about 1.2% at 4:09 a.m. ET on October 29, and software and technology names including ServiceNow and Fortinet fell sharply after hours, according to published market data. CoStar Group (NASDAQ:CSGP) may be caught in that selling as well as any company-specific concern. Watch the earnings call commentary, analyst estimate changes and any clarification of the full-year outlook. Readers should treat the 14% to 15% decline as a fact and the cause as unresolved. Software and data subscription businesses are also valued on forward growth, so any hint of slowing can lead to a sharp repricing.

Where Things Stand

The shares of CoStar Group (NASDAQ:CSGP) fell 14% to 15% despite 14% revenue growth to USD 952 million, most likely because of guidance or expectations rather than the headline figure, but sources conflict and the cause is not verified. One recap says full-year guidance was raised and another says revenue guidance was weak. The next catalysts are the earnings call detail and analyst revisions. A fuller answer requires the exact guidance numbers and consensus comparison. This is not investment advice.