X0609 4 2026-08-12 false 0001503274 Quanterix Corp QTRX 0001207928 DONNELLY WILLIAM P false C/O QUANTERIX CORPORATION 900 MIDDLESEX TURNPIKE BILLERICA MA 01821 true false false false false Common Stock 2026-08-12 4 P false 27155.00 2.75 A 27155.00 I See footnote Common Stock 2026-08-13 4 P false 72245.00 2.93 A 99400.00 I See Footnote The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $2.58 to $2.95, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. Owned jointly by trusts established by the reporting person and his spouse. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $2.85 to $3.13, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. /s/ Meghan Shevlin, Attorney-in-Fact 2026-08-14