Billions at stake on Apple-Google search deal

VIDEO2:3302:33
Billions at stake on Apple-Google search deal

The deal that makes Google's search engine the default option on Apple's Safari browsers expires soon, and that could be bad news for Google if the companies don't reach a new agreement.

Google could potentially lose billions in gross revenue if Apple switches to a different default search engine, according to a UBS research note Monday. Neither Apple nor Google have detailed when the agreement expires, but reports put the time frame in 2015, the note said.

Read MoreGoogle expands low-cost Android One smartphones

Google this year stands to bring in about $7.8 billion in gross revenue—about 10 percent of total revenue—from its existing search engine deal with Apple, according to UBS.

If Apple switches to a competitor, that could represent a 5 percent headwind, or about $3.9 billion, to 2015 gross revenue, the note said. UBS made those projections under the assumption that 50 percent of Apple iOS users switch their default search engine back to Google.