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FreeOpen source
Open-source stock market tools
What each licence actually allows — MIT, Apache, AGPL, GPL — and why open-source code almost never comes with open data.
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Open source solves the software, not the data
Every tool on this page ships source you can read, fork and run. None of them ships the market data, and that is the constraint that shapes the whole list.
Exactly one market-data API in the catalogue is open source — yfinance — and it is a client, not a source: it reads endpoints Yahoo publishes for its own website. The code is Apache-2.0; the numbers that come back carry no licence to redistribute at all, which its own maintainer says plainly. Everywhere else the pattern holds: the engine is open, the feed is bought.
The licence is the field to read first
MIT, Apache-2.0 — do what you like, keep the notice. Most of the agent and MCP layer sits here, along with Lightweight Charts and Plotly.js.
AGPL-3.0 — the condition triggers on network use. Run a modified copy as a service other people reach and you owe them the source. Ghostfolio, OpenBB and Backtesting.py are on these terms. Running one for yourself or your household never trips it; building a product on top of one is the case to check.
GPL-3.0, LGPL-3.0 — Backtrader is GPL, which reaches into anything you link it with. NautilusTrader is LGPL, which does not, provided you link rather than modify.
Split licences wear the label without covering the whole product. TimescaleDB is Apache-2.0 at the core, but compression, continuous aggregates, retention policies and gapfill are under the source-available Timescale License — which is to say the features you would install it for. Its card names the line.
Where the open tools cluster
Two categories are almost entirely open source: backtesting frameworks and algo trading libraries and financial MCP servers and AI agents. Both are categories where the product is the code.
Two are almost entirely closed: charting platforms and screeners and market data APIs. Both are categories where the product is a licence to show you somebody else's prices, and a licence cannot be forked.
The interesting middle is portfolio trackers, where Ghostfolio and Wealthfolio exist because the job — what you hold and what it is worth — is one you may not want on a vendor's server at all.
All 46 of them
Showing 46 of 46
LLM investor personas score a ticker, deterministic code sizes the book, nothing trades.
FreeOpen source
Real-time OLAP cluster built for high-concurrency dashboards, not for research joins.
FreeOpen source
Apache-2.0 general-purpose charting with a candlestick series and nothing else financial.
FreeOpen source
GARCH and the rest of the volatility-model family, plus the tests you need around them.
FreeOpen source
A single-instrument Python backtester — one OHLC series, one strategy, no live trading.
FreeOpen source
An event-driven Python backtester with 122 indicators, frozen since April 2023.
FreeOpen source
Python backtesting for allocation and rebalancing rules, not entries and exits.
FreeOpen source
Columnar OLAP database that keeps years of ticks on disk cheaply and scans them fast.
$66.52/moFree tierMCP
Macro series from 93 statistics offices and central banks behind one open API.
€1500/yrFree tier
In-process analytical SQL over Parquet tick files, with no server to run.
FreeOpen source
The maintained fork of Quantopian's empyrical — risk statistics, no plots.
FreeOpen source
Scrapes SEC, FINRA, FRED and CFTC data into your own Postgres and serves it over MCP.
$9.99/moFree tierMCP
Sessions, minutes and holidays for 69 exchanges, keyed by ISO-10383 code.
FreeOpen source
A one-call wrapper over Backtrader, dormant since 2023 and broken on PyPI.
FreeOpen source
Performance stats, drawdowns and portfolio weights from a DataFrame of prices.
FreeOpen source
Financial LLM adapters, instruction datasets and training notebooks, all MIT.
FreeOpen source
Open-source agents that turn a ticker and your own API keys into an analyst report.
FreeOpen source
Self-hosted open source portfolio tracking, or a hosted account for USD 48 a year.
FreeOpen sourceMCP
The community continuation of ib_insync — same API, new maintainers, TWS still required.
FreeOpen source
Line-protocol time-series database rewritten on Arrow, DataFusion and Parquet.
Free tier onlyOpen sourceMCP
Apache-2.0 canvas candlesticks with 27 indicators built in and zero dependencies.
FreeOpen source
The chart and nothing else — six series types on canvas, attribution required.
FreeOpen source
One strategy class for backtest and live, plus a built-in LLM agent runtime.
$24.50/moFree tier
Thirty-seven stock-analysis tools for any MCP client, on Yahoo data and no key.
FreeOpen sourceMCP
Rust core, Python API, one strategy that backtests and trades live unchanged.
Free tier onlyOpen source
One Python API, REST app and MCP server over thirty other people's data feeds.
$500/yrFree tierMCP
The DataFrame indicator library whose repo is gone and whose last release is a year old.
FreeOpen source
Candlestick and OHLC traces in an MIT library the notebook already has installed.
FreeOpen source
Prices in, weights out — efficient frontier, Black-Litterman and HRP.
FreeOpen source
An institutional-shaped Python backtester whose last commit to master was June 2024.
FreeOpen source
The open-source LEAN engine, plus a hosted cloud that runs it against real brokers.
$84/moFree tierMCP
The open-source derivatives pricing library banks actually use, reachable from Python.
FreeOpen source
HTML tearsheets and about eighty risk metrics from one pandas series of returns.
FreeOpen source
Open-source time-series SQL built for tick data — ASOF JOIN, SAMPLE BY, LATEST ON.
Free tier onlyOpen sourceMCP
Twenty-six convex risk measures, four objectives, one cvxpy-backed optimiser.
FreeOpen source
SEC filings and XBRL financials as MCP tools, under AGPL or a paid commercial licence.
FreeOpen sourceMCP
Portfolio optimisation as scikit-learn estimators — fit, predict, cross-validate.
FreeOpen source
The C indicator library everything else wraps — and pip now ships the C part with it.
FreeOpen source
Hypertables, columnar compression and continuous aggregates bolted onto plain Postgres.
$30/moFree tier
Analyst, bull, bear, risk and portfolio-manager agents argue over one ticker.
FreeOpen source
Screeners, technical analysis and backtests for any MCP client. No TradingView account.
$9/moFree tierMCP
A local finance research agent with 74 MCP tools, nine backtest engines and 14 brokers.
FreeOpen sourceMCP
Local-first portfolio and net-worth tracker for desktop, iOS and your own Docker host.
FreeOpen sourceMCP
The Python library everyone starts with — free, unofficial, and not something to build on.
FreeOpen source
The maintained fork of Quantopian's Zipline. Bring your own data — it ships almost none.
FreeOpen source
FAQ
Does open source mean free?
The software, yes. The data, almost never. QuantConnect publishes its LEAN engine under Apache-2.0 and charges a subscription for the hosted platform and the data that runs on it; Ghostfolio is AGPL and still needs a market-data provider behind it, most of which are paid. Read the licence for what you may do with the code and the provider's terms for what you may do with the numbers — they are two different questions with two different answers.
Can I use AGPL code inside a commercial product?
You can sell it, and you can modify it. What the AGPL adds over the GPL is that running a modified copy as a network service counts as distribution, so the people using that service can ask you for the source. For a desktop app, a personal server or internal use that condition never fires. For a SaaS product built on someone else's AGPL code it is the clause to take to a lawyer before you write the first line.
What is the difference between open source and self-hosted?
Open source is about the licence on the code; self-hosted is about where the process runs. They overlap heavily but they are not the same list. Every open-source tool in the catalogue can also be self-hosted, while six self-hosted ones are not open source at all — kdb+, Highcharts Stock, QuantRocket, ArcticDB, vectorbt and vectorbt PRO ship binaries or source-available licences you run on your own machine under commercial terms.
Which parts of the market are actually open source?
The parts where the value is in the code rather than in a licence to redistribute somebody else's prices. Backtesting frameworks and the MCP-and-agent layer are almost entirely open source; charting platforms, screeners and data vendors are almost entirely not. That split is not about culture — a screener's product is the feed it is licensed to show you, and a feed cannot be forked.