Why Open Interest Updates Only Once a Day

Open interest updates once a day, and the open interest figure sitting on a chain at 11 a.m. is the one that was true at the previous session's close. Volume is the live count: it moves with every print that crosses the tape. Open interest is a cleared and settled number, computed overnight by the Options Clearing Corporation, the single clearing house for listed US options, and distributed the next morning before the bell.

For the two definitions side by side, our options volume vs open interest guide holds the full comparison. This page is about the clock: what happens between the closing bell and the next morning's file, and what that timing stops you from measuring while the market is open.

Why open interest updates only once a day

Open interest counts the contracts that exist, not the contracts that changed hands. That count cannot be totalled from the tape. A print of 200 contracts crosses, and the tape does not say which of three things just happened. Both sides may have been opening, in which case 200 new contracts now exist. Both sides may have been closing, in which case 200 contracts just disappeared. One side may have opened while the other closed, in which case the total did not move at all. The same 200-lot print maps to three different outcomes for the figure in the OI column.

The one party that can tell those cases apart is the clearing house. Every side of every trade carries an opening or closing designation from the broker submitting it, and that designation travels to the clearing house rather than to the public tape. The cycle runs on a fixed daily schedule:

1. Trades print through the session and flow to the Options Clearing Corporation as members submit them.
2. After the close, the OCC matches and clears the day's activity, applying each side's open or close designation along with exercises and assignments.
3. Overnight, the OCC computes opening interest for every listed contract for the coming trading day.
4. The file goes out in the early morning, and brokers and data vendors load it ahead of the open.

No step in that chain can run mid-session. The clearing cycle settles once per day, and open interest steps once per day with it. A contract that trades heavily this afternoon still displays yesterday's opening interest on every screen until tomorrow morning.

Volume ticks all session while the OI column sits still

Volume is a per-session counter. It starts each morning at zero, only climbs, and is set aside at the close, at which point a fresh counter starts. The panel below takes every AAPL option contract that traded during June 2026 and totals each day's contract volume, with the number of distinct contracts that printed at least once alongside it.

SELECT
    toString(date)                        AS date,
    formatDateTime(toDate(date), '%b %e') AS date_label,
    round(sum(volume) / 1000, 1)          AS volume_thousands,
    countDistinct(ticker)                 AS contracts_with_volume
FROM global_markets.options_greeks
WHERE underlying_symbol = 'AAPL'
  AND date >= '2026-06-01'
  AND date <= '2026-06-30'
  AND volume > 0
GROUP BY date
ORDER BY date

Across that pinned window, from Jun 1 through Jun 30, the first session totalled 558.8 thousand contracts and the last totalled 1019.7 thousand, spread across 1429 separate contracts on that final day. Each of the 21 points on that line is an independent count that began at zero. Open interest behaves the other way round. It carries forward from the day before and moves in one overnight step, so plotting it on the same axis would draw a staircase, never an intraday curve.

Watch a single session up close and the asymmetry is plain. The panel below buckets one pinned trading day, June 16, 2026, into half-hour windows of New York clock time and tracks how that day's AAPL option volume accumulated.

SELECT
    formatDateTime(bucket, '%H:%i')                          AS et_time,
    round(bucket_contracts / 1000, 1)                        AS volume_thousands,
    round(100 * cumulative_contracts / session_contracts, 1) AS cumulative_pct
FROM
(
    SELECT
        bucket,
        bucket_contracts,
        sum(bucket_contracts) OVER (ORDER BY bucket) AS cumulative_contracts,
        sum(bucket_contracts) OVER ()                AS session_contracts
    FROM
    (
        SELECT
            toStartOfInterval(toTimeZone(sip_timestamp, 'America/New_York'), INTERVAL 30 MINUTE) AS bucket,
            sum(size)                                                                           AS bucket_contracts
        FROM global_markets.options_trades
        WHERE underlying_symbol = 'AAPL'
          AND sip_timestamp >= '2026-06-16 08:00:00'
          AND sip_timestamp <  '2026-06-17 04:00:00'
        GROUP BY bucket
    )
)
ORDER BY et_time

The first bucket with prints opens at 09:30 New York time, and by the end of it 17% of the session's contract volume had already printed. The cumulative column then climbs across 13 buckets to 100% at the end of the tape. Anyone refreshing a chain during those hours watched the volume column change on every refresh. The OI column beside it held a single value from the open to the close.

Who publishes open interest, and when

The OCC clears every listed US equity and index option, which makes its daily file the one source of the figure. Brokers and data providers redistribute that file. None of them compute their own version. The number is stamped to a trading day, and the convention is worth learning: what you read during Wednesday's session is the opening interest for Wednesday, computed from everything that cleared through Tuesday's close. Most platforms print it with no timestamp at all, which is the whole source of the confusion. The column looks as live as the one next to it.

Two practical notes follow from that stamp. A contract listed for the first time today shows zero open interest all day, however much it trades, since no completed clearing cycle stands behind it yet. And expirations, together with the assignments that follow them, land in the same overnight cycle, so the Monday figure after an expiration Friday is the first published look at which contracts survived.

What the once-a-day cadence stops you from measuring

The cadence has direct consequences for anything computed from the OI column during the session. You cannot infer opening versus closing intent intraday, since the designation that would tell you sits at the clearing house. A screen that ranks contracts by volume divided by open interest is dividing today's live count by yesterday's cleared count. The ratio is still informative, and it is worth naming precisely: a value above 1 means the day's trading exceeded the number of contracts that existed at the previous close. It does not mean the position count doubled.

To see how concentrated a single day gets, the panel below ranks the busiest AAPL contracts on that same pinned session by contract volume, with each one's share of the name's option volume for the day.

SELECT
    concat(
        formatDateTime(expiration_date, '%b %e'),
        ' $',
        toString(toUInt32(toFloat64(strike_price))),
        ' ',
        option_type
    )                                                               AS contract,
    round(contracts_traded / 1000, 1)                               AS volume_thousands,
    round(100 * contracts_traded / sum(contracts_traded) OVER (), 2) AS share_of_day_pct
FROM
(
    SELECT
        expiration_date,
        strike_price,
        option_type,
        sum(volume) AS contracts_traded
    FROM global_markets.options_greeks
    WHERE underlying_symbol = 'AAPL'
      AND date = '2026-06-16'
      AND volume > 0
    GROUP BY expiration_date, strike_price, option_type
)
ORDER BY volume_thousands DESC
LIMIT 12

The busiest contract on that list traded 113.3 thousand contracts, 12.91% of AAPL option volume for the session, and the last contract on the list traded 15.8 thousand, or 1.8%. Every one of those 12 contracts displayed an unchanged open interest figure for the whole day. Whether the activity added contracts or retired them cleared overnight and became visible the next morning. Screens built on this comparison get their own walkthrough in unusual options activity, and the chain layout that carries both columns side by side is covered in how to read an option chain.

One more consequence is worth stating plainly: a same-day jump in open interest is only ever visible tomorrow. Confirming that a large print opened new positions rather than unwound old ones takes one further session. If you would rather watch the prints themselves than the daily totals, the print-level view comes from a different source, and where to find options trade data covers it.

How the delay compares with equity short interest

One overnight cycle is quick against the other position figure retail screens carry. Equity short interest is compiled from broker reports on a twice-monthly settlement calendar and published days after each settlement date. The panel below lists the dated AAPL observations for the first half of 2026.

SELECT
    toString(settlement_date)                         AS settlement_date,
    formatDateTime(toDate(settlement_date), '%b %e')  AS settlement_label,
    round(toFloat64(max(short_interest)) / 1e6, 2)    AS short_interest_millions
FROM global_markets.stocks_short_interest
WHERE ticker = 'AAPL'
  AND settlement_date >= '2026-01-01'
  AND settlement_date <= '2026-06-30'
GROUP BY settlement_date
ORDER BY settlement_date

Between Jan 15 and Jun 30 the calendar carries 12 dated observations, roughly two a month, with 140.53 million shares short on the last of them. The gap between those points is the age a short interest number already carries before any publication delay is added on top. The mechanics of that calendar are in why short interest is two weeks old. Open interest, measured against it, is one sleep behind.

FAQ

Does open interest update in real time?

No. Volume updates with every print. Open interest updates once per trading day, from the clearing file computed after the previous session closed, and it holds that one value from the open to the close.

What time does open interest update each day?

The OCC computes the new day's opening interest overnight and publishes it in the early morning New York time, ahead of the 9:30 a.m. open. Brokers and data providers load the file before the session starts, which is why the figure you read at 3:59 p.m. is the same one that was there at 9:31 a.m.

Why does a contract show zero open interest after trading thousands of times today?

A newly listed contract has no completed clearing cycle behind it, so its published open interest stays at zero for the whole first day no matter how much volume prints. The next morning's file is the first one that can show what the day built.

Can I tell whether an option trade opened or closed a position?

Not from the tape during the session. The open or close designation travels with each side of the trade to the clearing house rather than to the public print. Its net effect appears in the next day's open interest.

Is open interest more delayed than short interest?

No. Open interest is one overnight cycle behind. Equity short interest is collected on a twice-monthly settlement calendar and published days after each settlement date, which leaves it weeks behind the market it describes.

Every panel above ships with the SQL that produced it, expand one to see exactly how the count was taken. To pin a session of your own and walk the volume build bucket by bucket, ask for it in plain English on the Strasmore terminal.