Christiane will review our financial results for the first quarter of 2026 before providing guidance. The prepared remarks will also be posted on the quarterly earnings section of our investor relations website following today's call. Lastly, all references to growth are on a year-over-year basis unless noted otherwise. We are well pleased with our excellent first quarter result, exceeding our guidance through strong execution and broader-based demand.
Billing growth 31%, total revenue increased 20%, and the product revenue grew 41%. Non-GAAP and GAAP operating margin were very strong at 36% and 31%, with GAAP operating margin and revenue growth total together 51%, one of the highest in the industry. We also generate a record $1 billion free cash flow, highlighting the strength and durability of our business model. GAAP earnings per share increased 29%, demonstrating our commitment to strong shareholder return.
OT security accelerated in the quarter with OT billing growth over 70% as customers prioritized on protecting critical infrastructure amid heightened threats. Given our strong results and confidence in the business, we are raising our 2026 guidance. We continue to expect balanced growth, strong cash generation, recurring revenue, and shareholder-focused long-term growth capital allocation strategy while consistently deliver GAAP profitability since IPO. As AI increase the demand for security, our platform approach continue to differentiate, supported by a strong direct operation model that enable us to turn supply chain challenges into opportunity to gain market share.