Core terms
High of day (HOD)
The highest trade price so far in the trading day. Whether premarket and after-hours trades count depends on the platform, so state which sessions an HOD includes.
"High of day" is used two ways. Some charts and quote screens use the regular session only (09:30–16:00 ET). Many small-cap traders and scanners use the full extended day from 04:00 ET, so a premarket spike can be the HOD even if the regular session never trades that high.
The time of the high matters as much as the price. In FennEdge's study of 671 gap-ups of 20% or more (2026-07-01 to 2026-10-02; as of 2026-10-02), 53.0% printed their extended-hours high before 09:30 and only 7.5% between 12:00 and 15:59 ET. FennEdge's Small-Cap Daily records HOD as the first one-minute bar that reached the day's high, 04:00 to the end of extended hours.
What traders should verify
When you say a stock "broke HOD," name the level (premarket high or regular-session high) and the time it was set. Odd-lot and late-reported prints can create highs that few traders could have traded at.
Do not conflate
Trader usage; no official definition. Different tools can show different HODs for the same stock on the same day because of session choice, bar size and trade-condition filters.
Primary source
Trader usage: there is no official definition, and platforms and tools may calculate it differently.