The best unified API platforms in 2025

A unified API platform can help you add hundreds of integrations to your product in a matter of weeks, helping you close deals, retain customers, expand to new markets, and save your engineers countless hours.

But unified API platforms differ widely from one another in meaningful ways, whether it's the types of integrations they support, the quality of their integrations, their tooling to manage integrations, and more.

To help you evaluate unified API solutions and identify the best one for your business, we’ll review the most popular options, along with their pros and cons. But to start, let’s break down how a unified API platform works.

What is a unified API platform?

A unified API platform provides a single, standardized interface to access multiple integrations within a software category (e.g., HRIS). And it abstracts the complexity of individual integrations by normalizing data models, authentication flows, rate limits, and pagination.

Some unified API platforms specialize in specific software categories. Rutter, for example, focuses on ecommerce and accounting, and Kombo only offers HRIS, payroll, and ATS integrations.

But other unified API solutions support several categories, and they’re constantly expanding to new ones.

In addition, some unified API platforms support specific industries. Codat, for instance, is focused on financial institutions.

Given the different types of unified API platforms that can exist, the market is getting saturated. Case in point: The G2 Grid® for Unified APIs now lists 23 vendors. Just 2 years ago, this grid listed less than 5 vendors.

https://www.merge.dev/blog/unified-api-examples?blog-related=image

Top unified API platforms

Here are some of the top unified API solutions to consider.

Merge

As shown in the G2 grid above, Merge is the clear leader in the unified API market. 

The unified API platform supports more than 220 integrations across 6 software categories and offers advanced features and support measures to ensure the integrations support your businesses’ use cases effectively.

Pros

• Integration observability: Merge offers the most advanced observability features to help your customer-facing teams identify, diagnose, and resolve integration issues. This includes a holistic dashboard to review integration health more broadly, fully-searchable logs to evaluate specific issues, and automated issue detection to address an issue

• Sync flexibility: You can sync any data from your customers’ applications through features like Field Mapping and Authenticated Passthrough Request

• White-glove support: Merge’s post-sales team not only addresses any issues quickly and proactively but also provides go-to-market support for launching your integrations—from pricing to marketing to supporting them

• Success with enterprise companies: Leading enterprise companies have seen success from using Merge. For example, Merge has case studies with brands like Ramp, BILL, AngelList, and Mistral AI

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Apideck

Apideck offers several unified APIs, including ATS, file storage, HRIS, and CRM.

Pros

• Integration marketplace offering: Their integration marketplace product lets you build and maintain different types of web pages that highlight your integration offerings and future integration plans, allows partners manage their own integration listings, and more 

• Support for ecommerce: Most unified API platforms don’t support integrations with e-commerce providers (e.g., Shopify), so if you provide a consumer-facing online store, Apideck can be one of your best—and only—options

• Affordability: Apideck’s pricing options are the cheapest in the space, making Apideck a good option for early-stage startups 

Cons

• Shallow integration support: While Apideck supports several software categories, they only support roughly 80 API integrations. In addition, they only support 50 common models (for context, Merge supports more than 80). Taken together, the platform may not be able to support your short or long term integration needs

• Unscalable pricing model: Apideck charges based on the number of API calls you make to their unified APIs. This means that as your business and that of your customers grow, the platform could become cost prohibitive

• Lack enterprise proof points: Apideck doesn’t have a single case study with an enterprise company, pointing to the platform’s inability to support enterprise-grade integrations 

https://www.merge.dev/blog/apideck-alternatives?blog-related=image

Kombo

Kombo is strictly focused on supporting HRIS, payroll, and ATS integrations through its unified APIs. 

Pros

• Focus on European integrations: Kombo is based in Europe and has heavily focused their integrations for European companies. For example, they support integrations with Teamtailor (Sweden-based), Onlyfy (German-based), and Factorial (Spain-based)

• Comprehensive coverage: While they only support 3 software categories, they cover 100+ integrations. So they’ll likely be able to support all the HRIS, payroll, and ATS integrations your prospects and customers care about and need

• Fast-growing company: Kombo is hiring across roles, including sales and post-sales. This points to the company’s current success and expansion plans 

Cons

• Limited integration observability support: Kombo doesn’t support features like automated issue or activity audit logs to monitor users’ activities in your account. They only provide API logs for the past 30 days

• Minimal custom field support: You can only sync custom data for specific common models, like Kombo’s Employee Model, and for specific integrations within those models. Since you’ll probably need to sync a wide range of custom employee and candidate data across your integrations, you likely won’t be able to use Kombo

• Narrow category focus: As your product matures, you’ll likely need to explore several integration categories that extend beyond what Kombo supports—whether that’s CRM, file storage, ticketing, or accounting

https://www.merge.dev/blog/kombo-alternatives?blog-related=image

Nango

Nango offers integrations across more than a dozen categories, including relatively niche categories for B2B SaaS companies (e.g., surveys)

Pros

• Free trial: You can have up to 10 integrated customers and sync thousands of records for free to help validate the integrations you plan on using  

• White-label integrations: All of Nango’s plans include a fully whitelabeled UI for authenticating an integration. This can reduce the friction of integration adoption—as your customers won’t be concerned about sharing data with a 3rd-party

• Diverse category support: You can find seemingly every category of integrations, making Nango a potential one-stop shop for all of your integration needs. For example, you can integrate your product with Garmin, Oura, Whoop and other athletic apps via Nango

Cons

• Shallow integrations: Nango’s focus has been on implementing as many integrations as possible and supporting as many categories as possible. As a result, their integrations typically don’t support many important endpoints 

• Unreliable syncs: Nango’s open-source model and small team can lead to frequent integration issues and slow fixes

• Compliance issues: Nango lacks some key compliance certifications that your customers might require—such as HIPAA

https://www.merge.dev/blog/nango-alternatives?blog-related=image

StackOne

StackOne offers unified APIs in 10 categories, including accounting, CRM, ATS, HRIS, and marketing software.

Pros

• Niche integration coverage: StackOne supports integration categories that are rarely supported by competitors, including learning management software (LMS) and instant messaging and email

• European presence: The company is based in London and most of their team members reside there, so they can offer effective support in European time zones

• Agentic support: StackOne offers hundreds of tools that AI agents can access via tools like OpenAI’s Function Calling feature

Cons

• No information on pricing: You can’t find any information online on StackOne’s pricing, making it impossible to assess whether StackOne even fits within your budget without having a formal sales conversation

• Lack of support for MCP: StackOne doesn’t currently offer a Model Context Protocol (MCP) server, preventing agents from using the protocol to access StackOne’s integrations

• Minimal presence in North America: If you need support in North American work hours and/or want to prioritize integrations that are popular within the region, StackOne likely won’t be a good fit. The vast majority of their employees are in London and most of their customers are in Europe

Unified.to

Unified.to is a fast-growing unified API solution that offers nearly 300 integrations across 20 software categories.

Pros

• Broad integration coverage: Offers relatively unique categories in the space, including data enrichment tools, generative AI solutions, and marketing automation platforms

• Agentic support: Unified.to’s recently-launched MCP server (e.g., “Unified MCP”) lets your AI agents access all of Unified.to’s integrations via tool calls

• Free trial: You can test their platform for free for 30 days—which is more than enough time to validate the platform and the use cases you need the integrations to support

Cons

• Basic integration coverage: Like some of the other solutions on this list, Unified.to has prioritized offering as many integrations as possible at the expense of providing deep coverage 

For example, they list out several unified data models across their category pages—but they don’t reveal the individual integrations that use those models. This lack of transparency likely signals that most integrations within a category don’t support all—if not most—of the unified data models

• Lack of enterprise readiness: Their list of customers include few enterprise companies. This signals that their integrations haven’t been tested at high data volumes. Their platform also lacks enterprise-grade security features, like activity audit logs and role-based access controls

• Negligible integration monitoring capabilities: There’s little to no mention of basic integration monitoring tooling on their site, such as API request logs or issue detection functionality, which may mean that they don't provide it

Final thoughts

Picking the best unified API platform can be an overwhelming exercise, as the decision has a significant impact on your product’s success—and, by extension, your business. 

Merge makes this decision easy by offering the most powerful integration observability features, enterprise-grade security controls and capabilities, battle-tested integrations, and responsive and strategic post-sales support.

Learn how Merge can transform your product integration strategy by scheduling a demo with an integration expert.