What is an IPO (initial public offering)? Definition, how it works and examples
A private company’s first sale of shares to the public — the steps from filing to the first trade, who sets the price, and what changes for the people who held before.
The short answer
The public IPO meaning is straightforward: an initial public offering is the first time a private company sells its shares to the general public, after registering the offer with the SEC — usually on Form S-1 — and listing the shares on an exchange such as the NYSE or Nasdaq, at a price it sets with its underwriting banks. For anyone who already holds the company — employees with options or RSUs, early investors, a vehicle that bought in privately — the IPO is not the day the money comes back. It is the day a public price appears.
What is an S-1 IPO, and how does the process run?
Under US securities law a company may not offer or sell shares to the public unless the offer is registered with the SEC or an exemption applies. An S-1 IPO is simply the standard route: the company files a registration statement on Form S-1, most of which is the prospectus investors will read. Foreign private issuers usually file the equivalent, Form F-1. The steps run in this order. Preparation The company mandates its banks, has its financial statements audited and builds the controls a public company needs.
IPOs in the stock market: why companies list, and what it costs them
Why do companies do IPOs? Three reasons, usually together. Capital: new shares sold in the offering raise money for the business. Liquidity: founders, employees and early investors get a market in which their shares can eventually be sold. And currency: listed shares can be used to pay for acquisitions and to compensate staff at a price everyone can see. Why IPOs are important to the wider market is the same point from the other side — they move a company’s ownership, and the information about it, into public view. Not every share in an IPO is new.
Examples of IPOs: one on paper, one from June 2026
How IPO shares work is easiest to see with numbers. The company below is invented; the arithmetic is the arithmetic of every underwritten offering. A real one: SpaceX priced its IPO on 11 June 2026 at a $1.77T valuation and began trading on Nasdaq as SPCX the next day. Six months earlier, an insider share sale had valued it at $800B. The full private-to-public sequence, and why the two valuations are not a return on one share, is set out in pre-IPO vs IPO.
What changes for pre-IPO holders when the company lists?
Four things change, and none of them puts cash in a holder’s hands on the first day. Share class Preferred stock usually converts into the listed common stock when the IPO closes, so the liquidation preference that protected it in a sale falls away. Lock-up Existing holders typically agree with the underwriters not to sell for a period — the SEC says typically 180 days. Terms, early releases and what happens at expiry are on the IPO lock-up page.
What is a pre-IPO marketplace, and what are the chances of getting an IPO allocation?
A pre-IPO marketplace is any venue where shares of a still-private company change hands before the listing: broker-run platforms that match buyers with employees and early investors, company-run tender offers, and pooled vehicles that buy a block and divide it. Every trade there is a secondary transaction that needs the company’s consent, and most are open only to accredited investors. The company being bought is what a pre-IPO company describes.
The rules and thresholds that apply, as of October 2026
Common mistakes Treating the listing as payday For an existing holder it usually starts a lock-up. Cash comes after it ends, at that day’s price. Reading SEC effectiveness as approval The SEC checks disclosure, not quality. A registered offering can still be a poor investment. Assuming the offer price is available Most individuals buy after trading opens, at the market price. Comparing the IPO valuation with the last round as a return New shares are issued in the offering. A higher valuation does not mean each share rose by the same amount.
The terms this page uses
Registration statement The filing — usually Form S-1 — that registers the offer with the SEC. Most of it is the prospectus. Underwriter An investment bank that buys the shares from the company at a discount and resells them to investors at the offer price. Indications of interest Non-binding orders collected on the road show: how many shares an investor would buy, at what price. Together they form the order book. Offer price The price at which shares are sold in the IPO, decided by the company on the underwriters’ recommendation.
What people ask about IPOs
What is a stock IPO, in one sentence? It is a private company’s first sale of shares to the public, registered with the SEC and followed by a listing on an exchange, after which anyone with a brokerage account can buy and sell the shares. What are IPOs in the stock market, and how many happen a year? They are the entry point of new companies to the exchanges. Counting only operating companies with an offer price of at least $5, Jay Ritter records 90 US IPOs in 2025; broader counts that include SPACs, funds and small listings are about twice that. How do IPO shares work after the first day?
What is a stock IPO, in one sentence?
It is a private company’s first sale of shares to the public, registered with the SEC and followed by a listing on an exchange, after which anyone with a brokerage account can buy and sell the shares.
What are IPOs in the stock market, and how many happen a year?
They are the entry point of new companies to the exchanges. Counting only operating companies with an offer price of at least $5, Jay Ritter records 90 US IPOs in 2025; broader counts that include SPACs, funds and small listings are about twice that.
How do IPO shares work after the first day?
They are ordinary listed shares, traded at market prices. What differs is supply: in the first months only the shares sold in the offering trade freely, and the rest arrive when lock-ups end and holding periods pass.
Does an IPO make a company a safer investment?
It makes it more transparent, not safer. The company reports quarterly and its price is visible every day, but the price can fall below the offer — including when underwriter support ends and when the lock-up expires.
What happens to my private shares or options at the IPO?
Preferred shares usually convert to the listed common, options stay options on listed stock, and RSUs waiting on a liquidity event start to settle. You are typically locked up for around 180 days before you can sell.
Where every figure on this page comes from
Figures were last verified on 2 October 2026. Rules are cited for the United States; exchange listing standards and other jurisdictions add their own. For the investor’s view of the same company before and after its listing, see pre-IPO vs IPO; for the underlying SEC text, the Investor Bulletin is short and worth reading in full.