What Is Short Volume? Reading FINRA's Daily Short-Sale Data

Short volume is the share of a stock's daily off-exchange volume sold short, a flow figure FINRA publishes after each session from broker-marked sell orders.

Short volume is quoted often and is frequently mistaken for short interest. This page covers what FINRA's daily file counts, how the ratio is built, why a reading near half is the ordinary case, what short exempt volume is, and why a symbol is compared with its own history. It is descriptive throughout.

What the FINRA daily file counts

Regulation SHO defines a short sale as "any sale of a security which the seller does not own or any sale which is consummated by the delivery of a security borrowed by, or for the account of, the seller." Rule 200(g) requires a broker or dealer to mark every sell order in an equity security as "long," "short," or "short exempt." Short volume is the sum of the shares behind the orders marked short.

FINRA publishes that sum once a session, per symbol, in its Regulation SHO daily short sale volume files. Each row carries the date, the symbol, short volume, short exempt volume, total volume, and a market field naming the facilities that reported the trades. FINRA's site holds the last 365 days in an interactive grid, with downloadable files and a query API for older history.

Two limits are built into the file. The first is that it counts trades, not positions: a share sold short at 10:02 and bought back at 10:03 is in the count, and the same share sold short again an hour later is counted again. The second is coverage: the file records trades reported to FINRA's off-exchange trade reporting facilities, so the total volume column is off-exchange volume rather than the consolidated volume of the session.

Short volume is not short interest

These two measurements answer different questions, and they are often swapped for each other.

Short interest is a position count. Firms report the open short positions on their books as of settlement dates around the middle and the end of each month, and the aggregate is published afterwards. It says how many shares are sold short and still outstanding, and it arrives twice a month on a lag.

Short volume is a flow count. It says how much of one day's reported trading was executed as short sales, and it arrives the same evening. A stock can print heavy short volume all week and show no change in short interest, which is what happens when the shorts opened during each session are closed before the close. The borrow, sell, repurchase and return mechanism behind a short interest position is covered in short selling, while much of daily short volume comes from market-maker activity that never involves a borrow at all.

The ratio, and why a reading near half is the ordinary case

The ratio is short volume divided by total volume for one symbol on one date, expressed as a percent. Nothing else goes into it.

A first-time reader tends to assume a 50% ratio means half the market is positioned against the stock. It does not. Much of daily short volume comes from intermediaries who hold no view on the company:

• A market maker that fills a customer buy order without holding the shares has made a short sale and marks it short, then buys the shares back within seconds or minutes. Firms doing this quote both sides of the bid-ask spread through the session.
• A dealer hedging an options book, a convertible position or an exchange-traded fund creation basket sells short as the hedge leg and unwinds it when the exposure changes.
• An arbitrage desk sells one leg short against a long leg, and the two legs close together.

None of that is an opinion about the company. Those short marks come from firms filling the gap when a buyer and a seller do not arrive at the same instant. Readings clustered around half are the normal state of this data.

Short exempt volume and the Rule 201 circuit breaker

The daily file reports short exempt volume in its own column, and that column runs far smaller than the short volume column. A sell order may be marked short exempt only when Rule 201(c) or Rule 201(d) applies.

Rule 201 is titled Circuit breaker. When an NMS stock falls 10% or more from the prior day's closing price as determined by its listing market, trading centers must stop executing or displaying short sale orders priced at or below the current national best bid, for the remainder of that day and the following day. Orders marked short exempt sit outside that restriction, and the Rule 201(c) and Rule 201(d) markings become available only after the listing market has made and published that 10% determination for the security under Rule 201(b)(3). The qualifying cases include an order already priced above the national best bid at submission, a seller deemed to own the security under Rule 200 who intends to deliver once restrictions on delivery are lifted, a market maker offsetting a customer odd-lot order, riskless principal executions and qualifying volume weighted average price orders.

Short exempt volume is therefore a marking category under Rule 201, and FINRA reports it in a separate column so the two markings can be read apart.

Why a raw ranking misleads, and a worked example

Sorting every symbol by its raw ratio produces a list of the market's thinnest names. A stock where two shares traded off-exchange and both were marked short prints 100%, outranking a heavily traded name whose ratio moved by a wide margin on millions of shares. Two corrections deal with that: a volume floor that drops symbols too thin for a ratio to mean anything, and a comparison of each symbol with its own recent history rather than with other symbols, since every symbol has a resting level set by how it trades and how it is hedged.

Take the trading session of 11 September 2026. Kresmion's coverage of the FINRA file for that date held 6,582 symbols. A floor of 100,000 shares of off-exchange volume left 3,484 of them, and among those the median short volume ratio was 53.5%.

Kresmion's public short volume tool applies that method to the symbols it covers. It ranks each of them by how far its ratio sits from that symbol's own trailing 20-session mean, measured in standard deviations, prints the day's median, and holds the stated 100,000-share floor with the thinner names one toggle away. It is a reading surface over the published FINRA data and it places no orders.

Read that way, a symbol at 53.5% on 11 September 2026 sat where the middle of the market sat. A symbol whose ratio had run well under the median for a month and then printed well above it on one session has moved, and the deviation figure states how far. Neither statement says anything about where the share price settles next.

Key takeaways

Frequently asked questions

Does a high short volume ratio predict a falling share price?

No. It describes one session and it does not forecast. Much of the count comes from market makers and hedging desks that open and close the same position inside the day, so a high reading says the session's off-exchange flow was heavy on the short side of the order marking rule. It says nothing about where the share price goes.

Why is short volume around 50% so often?

Because the count includes intermediaries. A market maker filling a customer buy order without inventory has made a short sale and marks it short, then buys the shares back minutes later, and hedging and arbitrage legs are marked the same way. Among the covered symbols above a 100,000-share floor on 11 September 2026 the median ratio was 53.5%.

Why can short volume be heavy while short interest does not change?

Because most of what the daily file counts never survives to a settlement date. A market maker that sells short to fill a customer buy order and repurchases the shares minutes later has added to that day's short volume while leaving the open short position unchanged. Short interest counts only the short positions still on the books when firms report them, so a week of heavy intraday short flow can leave it flat.

Does FINRA's file cover all trading in a stock?

No. It covers trades reported to FINRA's off-exchange trade reporting facilities, so exchange volume sits outside it. Both halves of the ratio come from that same off-exchange slice, which keeps the ratio internally consistent while meaning it is not a ratio of the stock's total daily volume.

Why compare a symbol's ratio with its own history rather than with other symbols?

Because each symbol has its own resting level, set by how it trades, who makes markets in it and how it is hedged. A reading that is unremarkable in a name which sits at that level every day is a wide move in a name that usually sits far below it. A volume floor plus that comparison keeps thin names from taking over a ranking on two-share prints. This page is information, not investment advice.

--- Source: FINRA. Regulation SHO daily short sale volume files, https://www.finra.org/finra-data/browse-catalog/short-sale-volume-data and the daily file for the 11 September 2026 session, https://cdn.finra.org/equity/regsho/daily/CNMSshvol20260911.txt , both read 2026-09-14. Short sale definition and order marking, 17 CFR 242.200, https://www.ecfr.gov/current/title-17/chapter-II/part-242/subject-group-ECFR1607681c7b4f78d/section-242.200 . Circuit breaker and short exempt conditions, 17 CFR 242.201, https://www.ecfr.gov/current/title-17/chapter-II/part-242/subject-group-ECFR1607681c7b4f78d/section-242.201 . Symbol counts, volume floor and median ratio, Kresmion /tools/short-volume, trading session 11 September 2026, read 2026-09-14. Kresmion Research.