SCHEDULE 13G/A

Klaviyo Inc

Series A Common Stock, par value $0.001 per share · CUSIP: 49845K101

Event date: 2025-09-30

Reporting persons may disclose overlapping interests. Their amounts are shown individually and are not added into a filing total.

Filing-level shares

Unavailable

Percent of class

Unavailable

• Summit Partners Growth Equity Fund IX-A, L.P.

  Shares: 11,142,414 · Class: 7.11%

• Summit Partners Growth Equity Fund IX-B, L.P.

  Shares: 6,957,168 · Class: 4.44%

• Summit Partners Co-Invest (Kiwi), L.P.

  Shares: 687,035 · Class: 0.44%

• Summit Investors GE IX/VC IV, LLC

  Shares: 58,561 · Class: 0.04%

• Summit Investors GE IX/VC IV (UK), L.P.

  Shares: 7,600 · Class: 0.01%

• Summit Partners, L.P.

  Shares: 18,852,778 · Class: 12.03%

Amounts are as disclosed in this filing. Schedule type alone does not establish investment intent.