Prompt
Are there any historical price data APIs that include deep historical coverage and corporate action adjustments?
Latest observation
Yes — several APIs do, though the exact combination of deep history + corporate-action-adjusted prices varies a lot by vendor and asset class.
Good candidates
1) Polygon.io
- Coverage: strong for US equities; intraday and daily history depending on plan
- Adjustments: supports split/dividend-adjusted data for aggregates
- Best for: modern developer-friendly API, equities focused
2) Tiingo
- Coverage: long daily history for many US equities/ETFs
- Adjustments: adjusted prices included; split/dividend data available
- Best for: clean end-of-day equity data with adjustments
3) Nasdaq Data Link / Quandl datasets
- Coverage: depends on dataset, some go very deep historically
- Adjustments: many premium datasets are adjusted; corporate actions often included separately or baked in
- Best for: flexibility, research workflows, alternative vendors
4) Alpha Vantage
- Coverage: decent, but not as deep or robust as institutional sources
- Adjustments: adjusted daily series available
- Best for: lightweight use, prototyping
5) EOD Historical Data
- Coverage: broad global equities with long history
- Adjustments: adjusted OHLC data and corporate actions
- Best for: international equities and reasonably deep history
6) Intrinio
- Coverage: broad market data products, depth varies by package
- Adjustments: corporate action-aware pricing options
- Best for: professional use, enterprise integrations
7) Bloomberg / Refinitiv / FactSet / S&P Capital IQ
- Coverage: very deep, institutional-grade
- Adjustments: extensive corporate action handling
- Best for: institutional research/compliance-heavy environments
- Tradeoff: expensive and licensing-heavy
What to check when comparing
To make sure an API really fits your use case, verify:
- Adjusted close vs adjusted OHLC
- Whether adjustments are split-only or split + dividend
- Whether the vendor provides raw prices and corporate actions separately
- Survivorship-bias-free coverage for delisted securities
- History depth: daily back to IPO, or only a limited window
- Support for global markets if needed
Quick recommendation
- If you want a developer-friendly API: Polygon or Tiingo
- If you want global/long history: EOD Historical Data
- If you want institutional-grade depth: Bloomberg/Refinitiv/FactSet
If you want, I can also give you a comparison table of the best APIs by:
- history depth
- adjustment quality
- pricing
- ease of use
- asset class coverage
Observation history
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