US instruments only. Picks which instrument a ticker refers to, as of the given date (format yyyy-mm-dd).
What it does: changes instrument resolution only. It does not filter or move the returned data — that stays controlled by the endpoint's own data parameters (such as from_date / to_date, or as_of_date on the options endpoints). Think of it as answering "who owned this ticker on this date?", not "what data do I want back?".
Why you need it: tickers get reused, renamed and delisted over time (e.g. FB → META; SPLK was delisted when Cisco acquired Splunk). By default the endpoint matches the ticker on the exchange in the URL path to the currently-active instrument — so a ticker that no longer trades returns 404, and a recycled ticker resolves to today's owner, not the historical one.
When set: the URL path exchange is ignored and all US exchanges are searched for whichever instrument held the ticker on that date. This lets you pull history for a company that has since changed ticker, delisted, or moved exchange.
Rules:
- Omitted → current behaviour, exactly unchanged.
- Present (any value, even blank or a future date) → as-of resolution is applied; a blank value defaults to today.
- A non-US exchange / MIC / country code combined with this parameter returns 400.
Note: on the options endpoints this is distinct from as_of_date, which filters the option data snapshot — ticker_as_of_date only selects the instrument.
