Glossary
All-time high
The highest price a security or index has ever reached; a stock at an all-time high has no overhead resistance from past buyers.
An all-time high (ATH) is the highest price at which a stock, fund, index or other asset has ever traded or closed. Headlines about the S&P 500 or the Dow "hitting a record" refer to an all-time high. The level matters to traders because above it there are no earlier buyers sitting on losses who might sell as soon as they break even.
How it is measured
Two conventions exist, and quote pages do not always say which they use:
- Intraday ATH: the highest price printed during any session.
- Closing ATH: the highest official closing price, which is what index providers and most news reports cite.
For individual stocks, historical prices are normally split-adjusted, so a stock that traded at $600 before a 4-for-1 split shows that old high as $150. Some providers also adjust for dividends, which lowers older prices slightly. Comparing an ATH from one site with a price from another can therefore mislead.
What it does and does not mean
A market at all-time highs is not automatically "due" for a fall. Broad US indexes have spent long stretches setting record after record, because a rising long-term trend naturally produces new highs. On the other hand, some individual stocks never revisit their peaks: many dot-com era leaders still traded below their 2000 highs decades later. The phrase describes where price has been, not where it is going.
Traders sometimes call price action above an ATH "blue sky" territory and watch whether the old peak flips from resistance into support on a pullback.