The accompanying earnings call presentation is available on the investor relations section of the company's website. Reconciliations of these measures to GAAP measures are available in earnings release and supplemental presentation on our website. We are off to a solid start to the year, and I am pleased to report that our Q1 financial results have us on pace to achieve our full-year guidance. From a growth perspective, the quality composition of our revenue continued to improve.
Organic ACV growth was 1.6%, with subscription organic revenue growth of 1.7%, reflecting increased adoption of subscription-based solution across Clarivate. Adjusted EBITDA was $241 million, representing a 41% margin, up almost 200 basis points year-over-year, highlighting the benefit of our subscription-first strategy and disciplined cost management. Free cash flow generation was also solid at approximately $79 million, which allowed us to retire $143 million of debt during the quarter. This quarter reinforces our confidence that the actions we put in place are beginning to translate into more predictable performance, expanding margin, and strong free cash flow generation.
You can see these pillars showing up clearly in the numbers through subscription mix, margin expansion, and debt reduction. Academia and government continue to be a strong engine for recurring revenue growth. Adoption of our ProQuest subscription solution remains strong with over 600 new subscriptions sold in the last 12 months, reinforcing the durability and predictability of our revenue base. Sales execution is also improving, driven by more effective cross-sell execution across content, research and analytics, and software solution.