Thank you for standing by. My name is Gail, and I will be your operator for today's call. At this time, I would like to welcome everyone to the Backblaze First Quarter 2025 Earnings Call. All lines have been placed on mute to prevent any background noise. After the speaker's remarks, there will be a question-and-answer session. If you would like to ask a question during that time, simply press star followed by the number one on your telephone keypad. If you would like to withdraw your question, kindly press star one again. It is now my pleasure to turn today's call over to Mimi Kong, Head of Investor Relations. Please go ahead.
Thank you. Good afternoon, and welcome to Backblaze's First Quarter 2025 Earnings C all. On the call with me today are Gleb Budman, Co-founder, CEO, and Chairperson of the Board, and Marc Suidan, Chief Financial Officer. Today, Backblaze will discuss the financial results that were distributed earlier. Statements on this call include forward-looking statements about our future financial results, the impact of our go-to-market transformation, sales and marketing initiatives, cost savings initiatives, results from new features, the impact of price changes, our ability to compete effectively and manage our growth, and our strategy to acquire new customers, retain and expand our business with existing customers, impact of changes to global trade policies, and third-party attempts to generate negative news regarding the company regardless of accuracy.
These statements are subject to risks and uncertainties that could cause actual results to differ materially, including those described in our risk factors that are included in our quarterly report on Form 10Q and our other financial filings. You should not rely on our forward-looking statements as predictions of future events. All forward-looking statements that we make on this call are based on assumptions and beliefs as of today, and we undertake no obligation to update them except as required by law. Our discussion today will include non-GAAP financial measures. These non-GAAP measures should be considered in addition to and not as a substitute for our GAAP results. Reconciliation of GAAP to non-GAAP results may be found in our earnings release, which is furnished with our Form 8K filed today with the SEC.
You can also find a slide presentation related to our comments in the webcast, which will also be posted to our Investor Relations page after the call. Please also see our press release or presentations for definitions of additional metrics such as NRR, Gross Customer Retention Rate, ARPU, and Adjusted Free Cash Flow. We will be participating in Needham's Tech Conference on May 13st in New York and the Craig-Hallum Conference in Minneapolis on May 28th. Looking forward to seeing some of you in person. Thank you for joining us, and I would now like to turn the call over to Gleb.
Thank you, Mimi, and welcome everyone to the call. We delivered strong results this quarter and are building towards a strong year overall. In Q1, revenue and adjusted EBITDA margin beat the high end of guidance. Overall, company revenue grew 15% over the same period last year. B2 Cloud Storage, which is now the largest part of our business, continued to gain momentum, with organic growth accelerating for the 2nd consecutive quarter and achieving 23%. We're not only driving growth, but also the bottom line. Our adjusted EBITDA margin tripled over the same period last year to 18%, and we've made substantial progress on improving our adjusted free cash flow from negative 13% in the fourth quarter to negative 6% in the first quarter.
By combining B2 revenue growth and adjusted free cash flow margin in a single quarter from Q4 to Q1, we've moved from 9% to 17%, a great step toward becoming a Rule of 40 company. Looking ahead, we continue to be on track to accelerate B2 growth each quarter, reaching at least 30% by Q4 of this year, and to achieve adjusted free cash flow positive in Q4 as well. In a moment, I'm going to talk about AI and why we're excited about Backblaze's ability to continue to deliver superior services for its customers and superior performance for its investors. 1st, I think we need to take a moment and talk about a recently published misleading report that relied on false claims by two disgruntled former employees, one of whom was fired for poor performance and the other for gross misconduct.
We believe reports like this are part of a common market manipulation scheme in which short positions are taken ahead of issuing a deceptive and distorting report, which, when published, is intended to push the share price down, allowing a market manipulative profit at the expense of everyone else. The claims in that report alleged the company's financials were untrustworthy. Those claims were false when they were made last October in self-serving lawsuits by two disgruntled employees, and they were still false when this report repeated them. Following industry best practices, the Audit Committee previously retained an independent law firm and a forensic accounting firm to review the financial claims. Those reviews confirmed there was no wrongdoing or issues with the financials. We have also since filed two fully audited annual financial statements, which are publicly available on our Investor Relations site and the SEC website.
Market manipulation schemes hurt retail investors, pension funds, and others. That's why accurate information is so important to investor decisions. We are building a great company, and these false claims won't derail Backblaze's growth story. Now, let's focus on why we're excited about our company, starting with the overall business and with our success in AI. I've previously said that Backblaze is a great platform for AI use cases because we provide a high-performance, low-cost storage platform that supports the open cloud, thus enabling customers to leverage the best GPU providers and other AI services out there rather than being locked into and limited by a walled garden. That value proposition continues to resonate. Our AI customer base grew by 66%. Their data with us grew by 25 times, and AI use cases represented the fastest-growing piece of our business in the first quarter.