Delayed data

How it works

A delay is a licensing category, not a technical state. The consolidated tape's delayed market data policy defines delayed last sale information and delayed quotation information as last sale or quotation information that has been delayed for such period as NYSE, for Network A, or NYSE American, for Network B, specifies on sixty days' written notice. The period is currently fifteen minutes after the markets first make the information available — which is where the convention comes from, and also why it is a convention: a venue can change it by giving notice.

Nasdaq's own policies show how little the fifteen-minute figure generalises. They recognise four treatments applied per product: fifteen minutes, twenty-four hours, midnight local time, and not eligible for delayed pricing. Midnight local means the time zone the information was released from, not yours. Anything disseminated before the interval is real-time, whatever a page calls it.

Two things travel with the category rather than with the clock. The exchanges keep their proprietary interest in the numbers: the tape's policy states that the passage of time does not alter a participant's interest in its last sale, quotation or index information, so delayed data is licensed, not public. And a delay must be declared. Vendors must ensure each device displaying delayed information conspicuously carries a statement that it has been delayed by at least the delay period — "Prices Delayed 15 Minutes" is the phrasing the policy accepts — and Nasdaq asks for the message at or near the top of the page, interspersed at least every ninety seconds on a ticker.

What falls away at the delayed end is the per-user apparatus. Display unit fees do not apply to a delayed interrogation or ticker service, professional or non-professional. Subscribers can be given delayed interrogation and display services without executing a subscriber agreement with NYSE or NYSE American, where a real-time service requires one from every subscriber. On Nasdaq's side, distribution after the delay interval may cease to be fee liable and may no longer need to be reported monthly at all — which is to say the entitlement stops being counted. On Nasdaq's price list published in January 2025, delayed data products are 50 dollars a month per firm with no per-user fee.

Two carve-outs are worth knowing. Index information gets none of this preferential treatment: the tape's policy says plainly that the same contract requirements apply to delayed index values as to real-time ones, so an index number on an otherwise delayed page can pull subscriber agreements back in. And real-time consolidated volume per issue may be distributed alongside delayed last sale or quotation information at no additional charge, which is why volume so often looks live on a page whose prices are not.

What breaks on it, and what does not

It breaks anything whose answer depends on the current spread. Order placement and routing, stop and alert logic keyed to a level, anything arbitrage-shaped, and any display a user will compare against their broker's screen while a stock is moving. A fifteen-minute-old best bid is not a stale version of the NBBO; it is a different number, and on a volatile open it is a materially different one.

It breaks nothing in most of the rest of this catalogue. Screeners, portfolio trackers, dashboards, research notebooks, fundamentals work and every backtest are unaffected — a backtest is delayed data by construction. Daily bars are identical whether they arrived at 16:00 or the following morning. End-of-day and delayed feeds are what the visible free layer of financial data is built on, which is why the cheap APIs in this category are so often described as delayed rather than priced as real-time.

Why it matters here

Read a card's latency field as a licence, not as a performance claim. "Delayed" on a card means the vendor bought the cheap product, so the price you are quoted is real and will stay real as your user count grows; "real-time" means per-user counting starts, and the professional or non-professional answer then multiplies it. The honest question is not whether you would prefer live data but whether anything you are building changes its output on a fifteen-minute-old price.

Two consequences. If the data is going in front of other people, delayed is usually the only version you can afford to show at all — the reason is redistribution, priced per feed. And if a program rather than a person acts on the number, the delay does not exempt you from the other expensive word, non-display use, where the licence follows the consumer rather than the clock.

What real-time market data costs has the full stack, and what is genuinely free covers the sources whose terms are lighter still.