Top 18 API startups that are taking over in 2025

What are API startups?

API startups build specialized digital tools that other businesses can easily plug into their software. Instead of making every business create its own payment system, email service, or data analyzer, these startups offer ready-made solutions through APIs. Stripe is a perfect example of this, they focused solely on making online payments simple and grew into a company processing billions just by mastering that single service.

Top API startups

Complete list of the most API startups that are worth knowing:

Contentful

Founded in 2013, Contentful offers a content management platform designed for delivering digital experiences. Their tools allow teams to create, manage, and distribute content via developer-friendly APIs.

The Contentful system structures content so it can be delivered across multiple channels like web, mobile, wearables, and digital displays. APIs enable seamless integration with existing infrastructure to display dynamic content. Content authors focus on optimizing experiences while developers work unencumbered.

Harness Inc

Founded in 2017, Harness is a software company aiming to transform how engineers build and deploy applications. Their platform uses automation and intelligence to simplify and accelerate the software delivery process.

The Harness software tracks code from development to production. It catches errors early through automated testing tools and helps resolve issues quicker with machine learning-powered diagnostics. These capabilities allow faster, more reliable delivery of new features and fixes.

OpenSea

Founded in 2017, OpenSea is an online marketplace for buying and selling non-fungible tokens (NFTs). It aims to be the most trusted platform for NFT trading through an inclusive peer-to-peer model.

On OpenSea, digital artists and creators can mint new NFTs with just a few clicks. Collectors can browse, purchase and even resell unique digital assets like art, music, videos, virtual worlds and more. Transactions happen directly between buyers and sellers.

Alpaca

Founded in 2015, Alpaca is a financial technology company that offers an API platform for stock trading and brokerage capabilities. Their goal is to make automated, commission-free stock trading easy to integrate for developers.

The Alpaca API handles the complex mechanisms of accessing market data and executing trades through code. This allows engineers to build and launch stock trading features seamlessly. Startups and apps can incorporate real-time trading without infrastructure costs or regulatory overhead.

PubNub

Founded in 2010, PubNub operates a global data stream network that powers real-time communication for thousands of internet-connected devices and applications. Their infrastructure facilitates massive volumes of streaming message data to flow between apps, systems and IoT hardware.

The PubNub network handles over 3 million messages per second, reaching over 200 million endpoints monthly. Their data stream fabric allows companies to easily build real-time features like chat, alerts, GPS coordination and telemetrics across devices, clouds and platforms.

Finch API

Founded in 2020, Finch API is a service platform that connects software applications to core payroll and human resources business systems securely. Their integration tools allow companies to unlock and sync employee data with third party solutions.

Finch’s APIs facilitate the transfer of sensitive employee compensation and personal information between HR systems like Workday, Gusto, or BambooHR and authorized business apps. This provides developers the building blocks to retrieve real-time staff records to power features like payroll reconciliation, talent management, and benefits enrollment.

SEON Fraud Fighters

Founded in 2017, SEON provides fraud prevention and risk management solutions for industries like finance, crypto, and e-commerce. Their tools allow companies to customize fraud fighting modules into their existing platforms to reduce risk across customer transactions.

For banks, lenders, trading firms, and gambling sites, SEON delivers advanced threat detection to combat spoofing, bot attacks, money laundering, and account takeovers. Granular analytics track customer behavior to expose criminal activity without excess friction.

Lob

Founded in 2013, Lob offers print and mail delivery services through their cloud-based platform. Their technology lets businesses automate ordering and sending all types of paper mailings and promotional materials without upfront equipment.

The Lob API handles the connectivity between marketing systems, design files and production workflows to coordinate complex physical mail campaigns. Companies can integrate Lob’s platform to easily upload mailing lists, personalized letters or postcards to be printed and delivered at scale.

Traversing

Founded in 2023, Traversing.ai offers a new hotel operations platform meant to replace outdated legacy systems. Traversing brings together multiple critical hotel software tools into a single, centralized cloud-based solution.

Traversing handles all guest requests in real-time while also automating integral processes like housekeeping and scheduling. Staff can quickly view and serve various guest needs through one integrated dashboard, including room service orders and facilities issues. Managers get business insights to optimize operations and revenue through analytics tools.

Ubio

Founded in 2013, Ubio offers an automation platform that can turn any online process into an API. Their cloud technology allows developers to build workflows that replicate human tasks on websites and apps as automated services.

The Ubio system acts as a virtual assistant handling things like filling forms, entering data, scheduling transactions or controlling apps based on triggers and scripts. Workflows integrate via API without underlying system changes.

Finix Payments

Founded in 2015, Finix Payments provides payment processing infrastructure and tools to help software companies build their own payment solutions. The Finix API handles the complexity behind payment acceptance like merchant accounts, regulatory compliance, security controls, and bank connectivity.

This allows developers to embed customizable payment functionality quickly without managing backups for uptime and redundancy. Finix also enables easy integration with accounting software, CRMs, and other business platforms.

RapidAPI

Founded in 2014, RapidAPI is an online platform that allows developers to easily add backend functions and features to their apps without coding everything from scratch.

The RapidAPI marketplace has thousands of APIs across many categories that developers can integrate to enable complex capabilities. For example, developers can tap into machine learning algorithms, user authentication services, payment processing, communications tools and more.

APIGen

Founded in 2024, APIGen is a company that offers a platform to easily build and deploy application programming interfaces (APIs). Their tool called GenAI generates full API codebases in minutes complete with testing and documentation for developers.

Creating APIs from scratch can take days involving coding endpoints, establishing data structures, writing validations, and building documentation. With APIGen’s visual editor, developers map out API needs and GenAI handles implementation details behind the scenes.

Monogoto

Founded in 2017, Monogoto provides cloud infrastructure and cellular connectivity for developers and enterprises. Their platform enables building IoT devices and applications that require wireless data capabilities.

Connecting physical products like industrial sensors, fleet trackers or smart retail hardware to cloud apps typically involves configuration hassles around SIMs, carriers and protocol support. monogoto simplifies device-to-cloud connectivity.

Lean Technologies

Founded in 2019, Lean Technologies is a financial technology company offering an API platform to provide access to banking and payments infrastructure across the Middle East and North Africa (MENA).

Lean’s universal APIs allow fintech innovators to build products and services by integrating to core financial rails like bank accounts, wallets, know your customer (KYC) checks, credit scoring and more. This spares startups from negotiating separate deals with each bank and provider.

Wyng

Founded in 2010, Wyng is a software company that helps brands better understand and engage with their customers. Their platform makes it easy for marketers to create personalized, interactive experiences that connect with people at the right times.

The Wyng tools allow brands to capture customer preferences and other first-party data directly and then leverage that information to deliver more relevant messaging in real-time. This helps foster digital relationships that feel tailored and responsive.

Infisical

Founded in 2022, Infisical is a company working on open-source solutions for managing sensitive information like passwords, keys and tokens securely.

Handling secret material properly is important for security, but tricky to do right. Many teams use makeshift methods like storing secrets in shared documents or code repositories. This creates risk if passwords leak or unauthorized changes occur.

Hygraph

Founded in 2017, Hygraph provides a content federation platform that connects disparate systems using GraphQL APIs. Their technology enables different services and data sources to interoperate for unified content management and distribution.

Many stacks today consist of fragmented tools and repositories that don’t easily share information. Hygraph has a unique content federation approach, it can pull and push content from virtually any system or endpoint. This content remains composable and actionable using Hygraph’s GraphQL interface.

Conclusion

Now that we’ve come to the very end, one thing is certain, API startups don’t need fancy pitches or complicated business plans to succeed. The recipe is pretty simple, spot a problem that bugs people, build an API that fixes it well, and make it dead easy to use.