What is short interest?

Short interest is how much of a company's stock the market is betting against. On this site it is measured the way the UK regulator measures it: as a percentage of a company's issued share capital held in net short positions.

Short selling in one paragraph

A short seller borrows shares and sells them, hoping to buy them back later at a lower price, return them to the lender, and keep the difference. If the price rises instead, the short seller loses money, in principle without limit, because there is no ceiling on how high a share price can go. Short selling is legal, regulated, and a normal part of how markets function: it adds liquidity and lets investors express the view that a company is overvalued.

From positions to "short interest"

A fund's net short position in a company is its short exposure minus its long exposure, counting derivatives as well as shares. Regulators express it as a percentage of the company's issued share capital: a 1.2% net short position in a company with a billion shares outstanding is equivalent to being short 12 million shares, net.

Add up everyone's net short positions and you get a measure of total short interest. In practice no public number captures everything, because disclosure rules only count positions above a threshold. In the UK since 13 July 2026, the FCA publishes, for each reportable company, the sum of all individual net short positions of 0.2% or more: the aggregate net short position (ANSP). That number is what we track and chart.

What high short interest means, and what it doesn't

A high number tells you that sophisticated investors have significant money staked on the share price falling. It does not tell you why. Common reasons include doubts about profitability or debt, expectations of dilution, sector-wide pessimism, or hedges against related exposures. Some short positions are not directional bets at all, for example a market maker hedging a convertible bond.

Nor is a high number automatically bearish for the future: heavily shorted stocks sometimes rise sharply precisely because shorts have to buy back shares (see short squeeze basics). Research on whether short interest predicts returns is mixed. Treat the figure as a reading of positioning, not a signal.

How the numbers differ across markets

US "short interest" figures come from exchanges twice a month and count borrowed shares outstanding. The UK figure is different in three ways: it isdaily, it is based on positions notified to the regulatorrather than stock-loan data, and it only counts positions that individually reach 0.2% of issued share capital.Australia's number is daily and regulator-reported like the UK's, but with a far lower reporting floor (A$100,000 or 0.01%), so it is close to a complete census rather than a floor. Percentages from different markets are therefore not directly comparable.

Where our data comes from

Every number on this site comes from the FCA's official daily publication, archived on the day it appears. The methodology page documents the exact source, timing, and how corrections are handled.