Developer API

Alpaca is a technology platform that provides commission-free stock and crypto trading APIs for developers, enabling fintech companies, robo-advisors, and financial apps to offer trading capabilities without building broker-dealer infrastructure. Founded in 2015 and backed by Y Combinator and others, Alpaca has become the go-to platform for developers building trading applications. The Trading API provides programmatic access to buy, sell, and manage positions in US equities and cryptocurrencies with paper trading for testing. Market Data API delivers real-time and historical bars, quotes, trades, and snapshots for US equities from all major exchanges. Broker API enables fintech companies and financial advisors to offer trading to their customers, handling account opening, funding, order management, and reporting. Alpaca's commission-free model is made sustainable by payment for order flow and interest income. The platform supports fractional shares, enabling investment in any amount. Streaming WebSocket APIs provide real-time market data and order status updates. SDKs for Python and JavaScript are well-maintained with active open-source communities. Alpaca's developer community is particularly strong in the algorithmic trading space, with many open-source strategy libraries built on top of Alpaca's APIs. The paper trading environment faithfully replicates live trading mechanics. Alpaca serves thousands of individual developers and hundreds of fintech companies building automated trading and investment applications.

Braintree is a developer-first payment gateway acquired by PayPal in 2013 that powers payments for companies like Uber, Airbnb, GitHub, and OpenTable. Braintree offers a comprehensive SDK and API for accepting credit cards, debit cards, PayPal, Venmo, Apple Pay, Google Pay, and local payment methods through a single integration. Its client SDKs are available for iOS, Android, JavaScript, and all major server-side languages, enabling seamless mobile and web payment experiences. Braintree's Drop-in UI provides a pre-built, customizable payment form that handles PCI compliance out of the box, while the Hosted Fields integration offers pixel-perfect control while keeping sensitive card data off merchant servers. Advanced fraud tools include device fingerprinting, velocity checks, and real-time risk scoring. The Vault feature securely stores customer payment methods for streamlined repeat purchases. Braintree supports multi-currency processing and marketplace payments through its marketplace integration. The platform provides extensive webhook support for real-time payment event notifications. Braintree's sandbox environment faithfully replicates production, enabling thorough testing before going live. Integration with the broader PayPal ecosystem provides access to PayPal's consumer network and additional financial products. Braintree generally offers better rates than standard PayPal and is preferred by development teams needing more control.

Intrinio is a financial data platform that provides developers, analysts, and fintech companies with affordable access to market data, company fundamentals, ESG data, and alternative datasets through clean REST APIs. Founded in 2012, Intrinio has positioned itself as the accessible, developer-friendly alternative to expensive legacy data providers like Bloomberg and FactSet. The platform covers US equities, international stocks, ETFs, mutual funds, options, cryptocurrencies, forex, and economic indicators. Company fundamentals include standardized financial statements, calculated ratios, earnings estimates, and ownership data going back decades. Real-time and delayed quotes are available from major US exchanges. Intrinio's Excel Add-In enables analysts to pull live data into spreadsheets without coding. SDKs for Python, JavaScript, Ruby, Java, and other languages accelerate integration. The Data API provides flexible querying of financial data points. ESG and sustainability data has become increasingly prominent. Alternative datasets include web traffic, app downloads, and other non-traditional financial signals. Intrinio's pricing is significantly more accessible than traditional financial data providers, making it viable for startups and individual developers. The company provides excellent documentation and a responsive support team. Intrinio is popular with fintech startups building investment apps, financial analysts building custom models, and developers creating financial tools. Its free tier enables experimentation before commitment.

Lithic (formerly Privacy.com for Business) is a card issuing platform that provides fintechs, startups, and enterprises with the infrastructure to launch Visa debit and credit card programs through a simple API. Founded in 2014, Lithic has built a developer-first card issuing platform known for its clean documentation, fast integration, and flexible spend controls. The platform enables businesses to issue single-use, merchant-locked, and category-locked virtual cards for expense control and vendor payments. Physical card programs support both instant-issue and personalized cards for consumer and commercial products. Lithic's spend controls are programmable in real time, enabling complex authorization logic for expense management platforms, BNPL products, and financial services applications. The platform's sandbox environment provides full production parity for testing. Lithic handles the BIN sponsorship, card network relationships, and regulatory compliance so clients can focus on product development rather than infrastructure. The company offers both white-label and co-branded card programs. Integration with popular BaaS platforms and accounting tools simplifies financial operations. Lithic has processed billions in card volume and serves dozens of fintech companies. Its developer-focused approach, with comprehensive API documentation and responsive support, makes it particularly popular with engineering-led companies building financial products.

Marqeta is the leading modern card issuing platform, powering the payment cards for companies like DoorDash, Instacart, Square Cash App, Uber, and Klarna. Founded in Oakland in 2010, Marqeta pioneered just-in-time (JIT) provisioning—the ability to fund cards in real time at the point of purchase with precise control logic. This innovation enabled entirely new payment experiences like gig worker instant pay, corporate virtual cards for specific vendors, and Buy Now Pay Later card-based products. Marqeta's open API platform allows clients to customize card behaviors with granular spending controls: transaction limits, merchant category restrictions, geographic limits, and real-time decisioning logic. The platform issues both physical and virtual cards on Visa, Mastercard, and Discover networks. Marqeta's tokenization capabilities support Apple Pay, Google Pay, and Samsung Pay. Its sandbox environment with complete testing capabilities enables rapid product development. Marqeta went public in June 2021. The platform processes hundreds of billions in volume annually and issues cards in 40+ countries. Key use cases include expense management (virtual cards with spending rules), disbursements (instant payouts to workers), lending (BNPL card products), and digital banking (neobank debit cards). Its revenue sharing model means clients earn interchange revenue on their card programs.

Merge is a unified API platform that enables B2B software companies to add hundreds of integrations to their product through a single integration build. While not exclusively financial, Merge is widely used for accessing HRIS, payroll, accounting, ATS, and CRM data—making it essential infrastructure for fintech and HR-tech companies. Founded in 2020 and backed by Addition, NEA, and others, Merge allows product teams to integrate with Workday, ADP, QuickBooks, Salesforce, and 200+ other systems through one normalized API. For financial applications, Merge's Accounting category covers QuickBooks, Xero, NetSuite, Sage, and other accounting platforms with a unified data model for companies, accounts, transactions, invoices, and payments. The HRIS and Payroll categories provide employee and payroll data from ADP, Workday, BambooHR, and others—critical for financial apps embedding workforce cost analysis. Merge's Magic Link enables end users to authenticate their integrations securely. The platform handles OAuth flows, credential management, data normalization, and API version management, eliminating integration maintenance burden from product teams. Field Mapping allows customers to customize how their source system data maps to Merge's standard model. Analytics track integration health and usage. Merge has become infrastructure for hundreds of B2B SaaS companies that need rapid, scalable integrations without building each individually.

Plaid's financial data API products provide developers with programmatic access to bank account data, transaction history, income verification, and investment data across 12,000+ financial institutions. Beyond its consumer-facing Link product, Plaid has built a comprehensive API platform for financial data use cases. Transactions provides enriched, categorized transaction history going back 24 months from connected accounts. Identity extracts and verifies account holder information for KYC purposes. Assets delivers a point-in-time snapshot of account balances and transaction history formatted for lending and verification workflows. Liabilities provides data on loans, mortgages, student loans, and credit cards. Investments gives access to brokerage, retirement, and investment account holdings. Income Verification uses bank data to verify income, supplementing or replacing pay stubs in lending workflows. Balance provides real-time account balance information for payment risk assessment. Signal predicts the likelihood of ACH return, enabling smarter payment decisioning. Plaid's API documentation is considered best-in-class, with comprehensive guides, SDKs, and sandbox environment. The company's network of institutional connections and developer-friendly tooling have made it the default choice for fintech developers needing financial data access. Regulatory compliance with GDPR, CCPA, and financial data regulations is built into the platform.

Polygon.io is a market data API platform providing real-time and historical data for stocks, options, forex, and cryptocurrencies. Founded in 2017, Polygon.io has built a developer-first market data platform with clean REST and WebSocket APIs, comprehensive documentation, and competitive pricing. The Stocks API provides real-time quotes, trades, aggregates (bars), and snapshots across all US equities. Historical data goes back decades for equity markets. Options data covers the complete US options market with Greeks calculation. Forex data covers all major and minor currency pairs with real-time rates. Crypto data aggregates from multiple exchanges for a comprehensive view. WebSocket streaming delivers real-time market data with sub-second latency. Polygon's Snapshot API provides a complete market state for all tickers at once—useful for scanning and screening applications. Company details, financials, dividends, and splits are available through the Reference API. The free tier provides historical data access, while paid tiers unlock real-time data and higher rate limits. Polygon's pricing is transparent and developer-friendly, with plans scaling from hobby projects to production applications. SDKs for Python, JavaScript, Go, Java, and other languages simplify integration. Polygon is particularly popular with quantitative analysts, algorithmic traders, and fintech developers who need reliable, affordable market data. Its API design and documentation quality receive consistently high marks from developers.

Routable is a business payment and AP automation platform designed for companies processing high volumes of vendor and contractor payments—marketplaces, gig economy platforms, and businesses with large supplier networks. Founded in 2017 and backed by Bain Capital Ventures and Coatue, Routable enables companies to send thousands of payments simultaneously via ACH, same-day ACH, wire, and check. The platform's mass payables capability handles batch payment files for 1,000+ recipients with single-click execution. Vendor onboarding collects payment information and tax documentation (W-9s) through self-service flows, eliminating manual data collection. Payment approval workflows ensure authorization before disbursement. Tax form generation creates 1099s automatically from payment data at year-end. Real-time payment tracking provides status updates for every disbursement. The developer API enables fully automated payment workflows integrated directly into business systems. Integration with NetSuite, QuickBooks, and other accounting platforms syncs payment data to the GL. Routable is particularly popular with marketplace businesses, creator economy platforms, and companies managing freelancer or contractor payment programs where manual payment processing becomes unscalable at volume. Its combination of high-volume processing, automated compliance (1099s, TIN verification), and clean API has made it a preferred choice for fintech and platform companies.

Stripe is the world's leading payments infrastructure platform, powering online and in-person commerce for businesses of every size. Founded in 2010, Stripe has become the default choice for startups, marketplaces, and enterprises needing reliable, developer-friendly payment processing. Its comprehensive suite includes payment acceptance across 135+ currencies, subscription billing, fraud prevention with Radar, financial reporting, and Connect for marketplace payouts. Stripe's APIs are renowned for their clean design and extensive documentation, enabling developers to go live in days rather than months. Beyond basic payments, Stripe offers Stripe Capital for business financing, Stripe Treasury for embedded banking, Stripe Issuing for virtual/physical cards, and Stripe Tax for automated sales tax. The platform processes hundreds of billions in payments annually and serves millions of businesses including Amazon, Shopify, Lyft, and Zoom. Stripe Checkout provides a pre-built, optimized payment page that consistently outperforms custom implementations in conversion rates. Advanced features like 3D Secure, dynamic 3DS, and machine learning-based fraud detection protect businesses globally. Its Dashboard provides real-time visibility into revenue, disputes, and customer data.

Unit is an embedded banking infrastructure platform that enables software companies to offer banking products—checking accounts, savings accounts, debit cards, and loans—to their customers without becoming a bank. Founded in 2019 and backed by Accel, Better Tomorrow Ventures, and Insight Partners, Unit provides the complete Banking-as-a-Service (BaaS) stack through a single integration. Unit's API covers account opening with KYC/KYB verification, FDIC-insured deposit accounts via partner banks, ACH and wire transfers, debit card issuing with spend controls, and lending origination. The platform's real-time event system delivers webhooks for every account and transaction event. Unit handles all compliance obligations including BSA/AML program, regulatory reporting, and bank relationship management. The white-label approach allows complete brand customization—customers experience the software company's brand, not Unit's. Unit's compliance infrastructure is a key differentiator, with in-house compliance officers and regular bank audits ensuring regulatory soundness. The platform serves companies building vertical SaaS with embedded banking, marketplaces adding financial services, and consumer apps offering spending accounts. Notable clients include Roofstock, HoneyBook, and NinjaTrader. Unit's transparent pricing and developer-friendly documentation have made it the preferred BaaS platform for many Series A–C companies.

Xignite is a financial market data platform that provides cloud-based APIs for accessing real-time and historical market data, reference data, and financial information. Founded in 2006, Xignite pioneered the delivery of financial data via REST APIs, disrupting the traditional Bloomberg terminal and data feed model. The platform covers equities, ETFs, mutual funds, currencies, commodities, fixed income, and alternative assets across global markets. XigniteGlobalRealTime provides real-time quotes from major global exchanges. XigniteGlobalHistorical offers decades of historical price data for backtesting and analytics. XigniteGlobalFundamentals delivers company financials, ratios, earnings, and corporate events. XigniteGlobalNews aggregates financial news from hundreds of sources. Xignite's API design prioritizes developer usability with RESTful endpoints, JSON responses, and comprehensive documentation. The platform handles data normalization across exchanges and instruments, eliminating the need for clients to handle inconsistent source data. Xignite serves fintech startups, wealth management platforms, robo-advisors, and investment analytics companies. Its cloud-native architecture scales automatically with demand and provides reliable uptime for production financial applications. The platform's pay-as-you-go and subscription options accommodate both startups and enterprise customers. Xignite has been instrumental in democratizing market data access that was previously available only to large financial institutions.