The U.S. Securities and Exchange Commission on Wednesday approved rule changes to allow the creation of bitcoin exchange-traded funds in the U.S., a long-awaited move that will give regular investors access to the controversial and volatile cryptocurrency.

The decision will likely lead to the conversion of the Grayscale Bitcoin Trust, which holds about $29 billion of the cryptocurrency, into an ETF, as well as the launch of competing funds from mainstream issuers such as BlackRock’s iShares and Fidelity. The first funds are poised to begin trading Thursday.

The approval may prove to be a landmark event in the adoption of cryptocurrency by mainstream finance, as the ETF structure gives institutions and financial advisors a familiar and regulated way to buy exposure to bitcoin.

“We think that the SEC approval, should we and others get it, is a green light for institutions. We’ve been talking to quite a few of them, and they’re much more interested now that the SEC effectively is paving the way,” Ark Invest CEO Cathie Wood said on CNBC’s “Halftime Report” on Monday. Ark Invest has partnered with 21Shares on a proposed bitcoin fund.

The decision comes after an official SEC social media account on Tuesday falsely said that bitcoin ETFs had been approved. The SEC said the account had been compromised.

The regulator has for years opposed a so-called spot bitcoin fund, with several firms filing and then withdrawing applications for ETFs in the past. SEC Chair Gary Gensler has been an outspoken critic of crypto during his tenure.

However, the regulator appeared to change course on the ETF question in 2023, possibly due in part to an August loss to Grayscale in a court decision that criticized the SEC for blocking bitcoin ETFs while allowing funds that track bitcoin futures.

“Importantly, today’s Commission action is cabined to ETPs holding one non-security commodity, bitcoin. It should in no way signal the Commission’s willingness to approve listing standards for crypto asset securities. Nor does the approval signal anything about the Commission’s views as to the status of other crypto assets under the federal securities laws or about the current state of non-compliance of certain crypto asset market participants with the federal securities laws,” Gensler said in a statement Wednesday.

Optimism around approval first reemerged this year after asset management giant BlackRock filed an application in June, leading to a flood of applications from its rivals. The partnership of Ark Invest and 21Shares has the longest active filing, and a deadline for the SEC on the fund in January led many industry experts to expect that the first bitcoin ETFs would be approved shortly after the start of 2024.

More than 10 different firms are now in the formal process toward a launch, with the competition to become one of the market leaders expected to include differing expense ratios and a heavy marketing blitz. Several firms have already cut their original proposed fee.

It is not guaranteed that all applications will lead to a fund entering the market. The Cboe website on Wednesday afternoon indicated that several of the bitcoin ETFs would begin trading on its BZX exchange on Thursday.

The anticipation of the ETF also appears to have boosted the price of bitcoin in recent months. Some crypto advocates believe the arrival of bitcoin ETFs will unleash new demand for asset class from types of investors who were previously scared off by concerns about custody and the safety of crypto-specific exchanges.

The approval of the ETFs comes after a year that saw major law enforcement action against crypto firms and industry leaders, including the conviction of FTX founder Sam Bankman-Fried and multiple actions against Binance and its founder Changpeng Zhao.