
Successful enterprises rely on the latest technology to drive their business operations, intelligence, and efficiency. Modern business applications cover a broad scope of functions, including Customer Relationship Management (CRM), Resource Planning (ERP), Process Management (BPM), Marketing& Advertising, eCommerce, Business Intelligence (BI), Storage, Data Analytics, Content Management, Accounting& Payments, Collaboration, Communication & Messaging, Security, Human Resources, and most recently, API Management.
Application Programming Interfaces, or APIs, are an important part of the building blocks for all of this technology. Developers looking to create, integrate, or enhance business applications such as email marketing software, messaging agents, digital signatures, accounting, document management, or countless other categories should check out the ProgrammableWebBusiness category for the best APIs to choose from. There, they will find hundreds of business APIs and other tools that may be useful.
In this article, we highlight twelve top business APIs, chosen by popularity from the visitors of ProgrammableWeb.
1. WhatsApp Business API
WhatsApp Messenger is an SMS replacement application owned by Facebook. The WhatsApp Business API provides a way for businesses to interact with and reach customers using end-to-end encryption. This enables messages and calls with security that allows only a business and the person it is communicating with to read or listen. A WhatsApp Business Webhooks API is also available.

Screenshot: WhatsApp
2. Workday API
Workday is a single system for finance, HR, and planning. Workday WWS API provides partner and customer developers with access to Workday's robust business services via standards-based web services. These web services provide operations for interaction with many critical areas of Workday, including benefits, organization, payroll, and recruiting.
3. Microsoft Graph API
Microsoft Graph makes it possible for developers and IT professionals to access many of Microsoft's services programmatically, all from one place. The Microsoft Graph API provides unified metadata, payload format, error handling, and SDKs to drive business productivity such as mail, calendar, contacts, documents, directory, devices and more.
4. Yelp Fusion API
Yelp is a crowdsourced business review platform. The RESTful Yelp Fusion API can be used to retrieve business reviews and ratings, location information, and photos. The API returns up to 1000 businesses based on the provided search criteria. Methods are available for address, neighborhood, ratings, reviews, hours of operation, prices, and attributes such as reservation, hot and new, gender-neutral restrooms, and waitlist. A Yelp GraphQL API is also available.

Screenshot: Yelp
5. Slack
Slack brings together all of a team's messages, files, and posts from Twitter, Dropbox, Trello, Google Docs, GitHub, and other services in one place. Slack comes with an API that allows users to integrate it with other third-party applications, a Real-Time Messaging (RTM) API for embedding real-time chat functionality within clients, and the company's SCIM API for managing users and groups. Also, see the large list of Slack SDKs available for developers.
6. Gmail
Google's Gmail API gives a developer access to Gmail mailboxes and the ability to send email. The API allows users to perform CRUD operations on email messages, attachments, drafts, threads, filters, archives, and labels. The API can be useful to migrate email accounts from other providers, automate message sending, standardizing digital signatures, and more.
7. MailChimp
MailChimp provides a complete email marketing software solution. The MailChimp API helps users sync campaign stats and subscriber information between MailChimp and a database.
8. Adobe Sign
Adobe Sign is a cloud-based electronic signature solution. The Adobe Sign API allows developers to integrate electronic signature features into applications. Developers can authenticate with OAuth access token to implement agreements, transient documents, views, search, workflows, and megaSigns. Adobe Sign was formerly known as EchoSign.
Also of Interest: 10 Notable eCommerce APIs
9. Exact Online API
Exact Online is an online business software for business owners and accountants. Exact Online offers packages for small businesses in manufacturing, wholesale distribution, and professional services as well as for accounting and CPA firms. The Exact Online REST API allows developers to incorporate Exact Online functionality into third-party applications. API services include CRM, assets, documents, accounting, payroll, projects, users, and more.
10. Xero API
Xero is an online accounting system designed for small businesses and their advisors. The Xero API gives users access to bank transactions, invoices, and reports through the internet or mobile devices. The API uses a RESTful approach and responds to requests in an XML or JSON format.
11. FreshBooks API
FreshBooks is an all-in-one small business invoicing and accounting solution. The FreshBooks API is an interface for accessing FreshBooks data using JSON. The API can be used to create web and desktop applications that integrate with an account. API methods are available to manage clients, invoices, expenses, estimates, reports, accounting and more.
12. Zendesk API
Zendesk provides businesses with software and communication tools. The Zendesk API enables developers to integrate the Zendesk platform into their applications. With this API, users of the applications will be able to use the core features of the Zendesk service, some of the features include managing authorization, groups, users, requests, & tickets, setting limits on calls, automating calls, access to call records and sessions plus much more.
The APIs listed above are just a small sampling of what can be found in the Business category in ProgrammableWeb's API directory. Check out more than 780 APIs, 1050 SDKs, and 490 Source Code Samples for business application development.