Best Free Unified APIs of 2025

Plaid is an international data network that powers tools used by millions of people to live a more healthy financial life. Our ambition is to facilitate an inclusive, competitive and mutually beneficial financial systems by simplifying payments and revolutionizing lending. Plaid works with more than 8,000 companies, including fintechs such as Venmo and SoFi and several Fortune 500 companies, to give people more control and choice over how they manage money. Plaid is headquartered in San Francisco and its network spans more than 12,000 institutions throughout the US, Canada UK and Europe.

Boss Insights provides global leading access to business customers’ financial data with a single connection to accounting, banking, commerce, payroll, tax and more (i.e. Quickbooks, Stripe, SalesForce, etc.). It’s used by fintechs and neobanks to gain 60% increased automation, 100% automated scoring, 51% faster funding and 5x faster renewals.

Merge enables B2B companies to add hundreds of integrations to their products, making it easy to access and sync their customers’ data. Instead of building and maintaining each integration in-house, your developers can save time by integrating once to Merge’s Unified API to add an entire category of integrations to your product in just weeks. Merge offers over 220 integrations in accounting, HRIS, ATS, CRM, file storage, and ticketing. Once you build into Merge’s API, you’ll automatically get access to every integration we add. Merge’s platform makes secure data access easy by normalizing data and handling authentication, pagination, and rate limiting so you don’t have to deal with the nuances of each integration. Merge supports the entire integration lifecycle after the initial build. Merge handles integration maintenance — catching and resolving any issues so you don’t have to worry about integrations breaking. With a suite of integration observability features in our Dashboard, your customer success team has full visibility and control over your product integrations. Thousands of companies like Handshake, Ramp, BambooHR, Remote, and Drata use Merge to power their integrations at scale, enabling them to unblock sales, reduce customer churn, accelerate time to market for new products, and save costs related to engineering resources spent on building and maintaining integrations. Merge adheres to industry-standard compliance frameworks including SOC 2 Type II and ISO 27001, and complies with privacy regulations like HIPAA, GDPR and CCPA.

We simplify the process of installing applications, tags, and integrations on your site while enabling you to monitor your analytics through a straightforward unified API. You can easily add or remove new third-party integrations by simply updating your stack, without needing to alter your code. We continuously introduce new integrations for you to explore each day. With Stackpile, you can track your customer event data and analytics, which will be automatically transmitted to all your connected applications, tools, and integrations. Keeping all your third-party applications and integrations current with the latest versions can be quite tedious, but Stackpile takes care of that for you. Our Unified Analytics API enables you to monitor custom events and user identities effortlessly. Stackpile helps you save time and reduce development expenses by routing data to all your applications and integrations, eliminating the need to implement each API individually. Typically, without Stackpile, you would have to add a separate code snippet for each integration you wish to install. After implementing Stackpile, you can seamlessly install any of our supported applications, tools, and integrations with just a single click, making the entire process efficient and user-friendly. This streamlined approach not only enhances productivity but also allows you to focus on other important aspects of your business.

Our integration platform, designed for code-first implementation, simplifies the complexities associated with navigating multiple APIs. Fusebit provides a range of connectors for the most widely used SaaS applications, and we continuously expand our offerings each week. Additionally, our open-source framework allows users to customize existing Fusebit connectors and develop their own integrations for any platform of choice. With Fusebit, there's no restriction on the systems you can link together! This product empowers developers to swiftly incorporate integrations into their applications using robust API components. It alleviates the challenges of working with various disparate APIs while preserving the agility and ease-of-use that a code-first approach provides. By addressing integration needs much like how Stripe caters to payment solutions, Fusebit becomes an essential tool for developers. Plus, you can enjoy the peace of mind that comes with complete control over your integrations.

Since our inception in 2010, we have consistently prioritized the support of our users. Collaboratively, we create APIs tailored to meet the needs of your expanding applications, ensuring they are fully equipped to thrive. Our API is designed for speed, delivering responses in under a second, which allows your application to continue processing without delay. By implementing a single API that consolidates multiple functions, we help you conserve both time and effort, enabling you to focus on further developing your application. Additionally, we meticulously track all requests to facilitate easier debugging of API calls, streamlining the implementation process. Currently, we operate in a production environment where developers can access specific URLs along with helpful sample code snippets. It is important to note that all endpoints are compatible with UTF-8 character sets; therefore, ensuring your application can manage these characters is essential for optimal performance. We are committed to making the integration process as seamless as possible for our users.

By utilizing a single API, you can seamlessly connect with both Google Calendar and Microsoft Outlook. Additionally, this API allows for integration with video conferencing platforms like Zoom and Google Meet, enabling you to add virtual meetings to your calendar events. The implementation of our API is straightforward, fitting effortlessly into your existing tech framework without requiring any new dependencies. You can make API requests using cURL or any other HTTP client you already have in place. The OAuth configuration process is user-friendly, requiring just a redirect URL for your application linked to Pyas. When establishing new accounts, Pyas will utilize this URL to guide users back to your application. You have the flexibility to generate as many API keys as necessary, with the added security of encryption and the option to set expiration dates for temporary keys. Start managing your calendar events effectively by using your API keys, ensuring a smooth and efficient workflow. This level of integration simplifies your processes and facilitates better collaboration across different platforms.

The Precise API delivers vital information regarding the financial status of business clients, encompassing historical data, current performance metrics, and future projections. Designed to integrate seamlessly with all major accounting platforms, the Precise API features real-time push and pull capabilities, making it an excellent choice for financial institutions, lenders, and fintech companies servicing small to medium-sized enterprises. In addition, the Predict as a Service add-on enhances the functionality of the Precise API by offering a sophisticated, white-label cash flow forecasting and scenario planning platform tailored for your business clients. By implementing a cash flow solution, you can ensure that your clients remain engaged with your brand, fostering a connection to their essential business data and financial requirements. This not only strengthens client relationships but also positions your offerings as indispensable tools for their financial management.

Smartcar's vehicle API provides a wide array of functionalities such as verifying mileage, managing electric vehicle charging, issuing digital keys, and tracking fleets, among various other capabilities. This platform empowers mobility companies to seamlessly connect their applications and services with smart vehicles. You can effortlessly access vehicle information and initiate commands using our user-friendly and secure car API. Features include monitoring a vehicle's location, confirming mileage, charging an electric vehicle, sharing virtual keys, and additional services. Through the Smartcar Connect process, users can easily and quickly associate their vehicles with your application in just four clicks from either a mobile app or web interface. Our comprehensive documentation and software development kits facilitate rapid integration of our car API across diverse technology stacks, ensuring a smooth onboarding experience for developers. With Smartcar, managing connected vehicles has never been more straightforward.

APIPark serves as a comprehensive, open-source AI gateway and API developer portal designed to streamline the management, integration, and deployment of AI services for developers and businesses alike. Regardless of the AI model being utilized, APIPark offers a seamless integration experience. It consolidates all authentication management and monitors API call expenditures, ensuring a standardized data request format across various AI models. When changing AI models or tweaking prompts, your application or microservices remain unaffected, which enhances the overall ease of AI utilization while minimizing maintenance expenses. Developers can swiftly integrate different AI models and prompts into new APIs, enabling the creation of specialized services like sentiment analysis, translation, or data analytics by leveraging OpenAI GPT-4 and customized prompts. Furthermore, the platform’s API lifecycle management feature standardizes the handling of APIs, encompassing aspects such as traffic routing, load balancing, and version control for publicly available APIs, ultimately boosting the quality and maintainability of these APIs. This innovative approach not only facilitates a more efficient workflow but also empowers developers to innovate more rapidly in the AI space.

Streamlined SaaS App Integrations Made Effortless. Kloudless is an advanced API integration platform that consolidates endpoints and data structures from various SaaS APIs, allowing you to write code just once and seamlessly connect your application with multiple SaaS providers. We have navigated the complexities of over 150 APIs on your behalf. Our expertise in communicating with and managing these numerous APIs means you can focus on your core product. Collaborate with us to ensure your application can connect with any SaaS solution your customers desire. Our Unified APIs simplify the integration process by harmonizing endpoints and data models from various SaaS APIs, enabling you to code once and integrate many. By abstracting the differences among numerous SaaS APIs, our Unified APIs facilitate rapid integration development, helping you bring new features to market faster. Additionally, we provide valuable features such as real-time activity monitoring and pre-built tools like the File Picker and Crawler, which are not always available from the SaaS providers themselves, further enhancing your integration capabilities. With Kloudless, you can maximize efficiency and deliver exceptional value to your users.

Our Accounting Data as a Service API allows you to connect to all major accounting service providers. You can quickly build and deploy your application with just a few lines code. Get more accurate and complete information about your customers for a fraction of the market price You can see what your customer sees directly from the source. A beautiful front-end module is available to collect accounting data from your customers in real time. It is optimized to optimize conversion rates. All major accounting software providers are supported. This allows you to access financial transactions, insights, and reports on your customers on-demand. Developers can begin within minutes and have their software deployed within hours. We created the easiest and fastest API to meet all your accounting data requirements.

Our platform, designed with developers in mind, offers the adaptability needed to support all of your integrations that interact with customers. Vessel efficiently manages vast amounts of data, processing terabytes and billions of API requests with ease. We take pride in our SOC2 compliance, which reflects our dedication to upholding exceptional security and trustworthiness in our services. All data is safeguarded through encryption both during transmission and while stored, utilizing encryption standards recognized across the industry. This commitment to security ensures that our clients can rely on us for their most sensitive information.

ChatterBox is a powerful API solution that integrates with major video conferencing platforms like Zoom, MS Teams, and Google Meet, enabling real-time transcription of virtual meetings. The platform supports multiple languages and generates audio recordings and call metadata, making it ideal for teams that need accurate, on-demand transcripts. With a flexible, pay-as-you-go pricing model, ChatterBox ensures that businesses only pay for what they use, offering a cost-effective transcription solution.

Billions of people. Trillions of connections. One API. The Nylas APIs are powering applications with email, calendar and contacts that sync from any inbox around the globe. Nylas is the only company that provides an API for all email, calendar and contacts integrations. Contact records can be updated with missing information. A connection graph can make intros more warm. To create a single data source, combine data from each address book.

Ship the integrations that your customers and prospects require now, and watch your revenue soar without compromising your core products. Deliver secure, deep, and powerful integrations with advanced observability features and security for all types of use cases. We never store any of your customer's data. You can also securely store their OAUTH2 access tokens in your AWS Secrets Manager accounts. OAUTH2 authentication keeps your customers' credentials safe while giving them the ability to revoke their access tokens at any time. Use your OAUTH2 client secrets and IDS to take control of branding and security. Your application will have full autonomy over authorization and access tokens. Avoid the headaches of juggling multiple APIs and complex data transforms. Simplify integration with a single API and data model.