Cloud-based software maker Salesforce.com said it would buy Demandware, which provides software to design e-commerce websites, for about $2.8 billion.
Salesforce's cash offer of $75.00 per share represents a 56.3 percent premium to Demandware's Tuesday closing.
Demandware's shares were up 52.1 percent at $73, while Salesforce slipped 2 percent to $82.00 in premarket trading on Wednesday.
The acquisition is Salesforce's largest to date, topping its $2.5 billion purchase of marketing software maker ExactTarget in 2013.
Demandware's clients include Lands' End Inc, L'Oreal SA and Marks and Spencer Group Plc.
"With Demandware, Salesforce will be well positioned to deliver the future of commerce as part of our Customer Success Platform and create yet another billion dollar cloud," Salesforce CEO Marc Benioff said in a statement.
The deal, slated to close in Salesforce's second quarter ending July, is expected to increase the company's 2017 revenue by about $100 million to $120 million.
Salesforce had forecast fiscal 2017 revenue of $8.16 billion-$8.2 billion in May.
(Reporting by Anya George Tharakan in Bengaluru; Editing by Saumyadeb Chakrabarty)