Exhibit 32.1

CERTIFICATION OF CHIEF EXECUTIVE OFFICER

PURSUANT TO RULE 13a-14(b) OR RULE 15d-14(b)

OF THE SECURITIES EXCHANGE ACT OF 1934 AND 18 U.S.C. SECTION 1350

In connection with the Annual Report of Qualys, Inc. (the “Company”) on Form 10-K for the year ended December 31, 2018, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Philippe F. Courtot, Chairman, President and Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that, to the best of my knowledge:

          (1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

          (2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date:	February 27, 2019
By:	/s/ PHILIPPE F. COURTOT
	Philippe F. Courtot
	Chairman, President and Chief Executive Officer
	Qualys, Inc.