What is API?
API (Application Programming Interface) is a set of rules, protocols, and tools that allows different software applications to communicate with each other. It defines how software components should interact, enabling developers to access functionality or data from other services.
Quick Facts
| Full Name | Application Programming Interface |
|---|---|
| Created | Concept from 1960s, modern web APIs from 2000s |
| Specification | Official Specification |
How It Works
APIs act as intermediaries that allow applications to talk to each other without knowing the internal workings of the other system. They can be categorized into different types: Web APIs (REST, GraphQL, SOAP), Library APIs, Operating System APIs, and Hardware APIs. Modern web development heavily relies on APIs for integrating third-party services, accessing databases, and building microservices architectures. APIs typically use HTTP/HTTPS for communication and JSON or XML for data exchange. API versioning strategies include URL path versioning (/v1/users), query parameter versioning (?version=1), and header versioning (Accept: application/vnd.api+json;version=1). URL path versioning is most common for its simplicity and cacheability. Semantic versioning (MAJOR.MINOR.PATCH) helps communicate breaking vs. non-breaking changes.
Key Characteristics
- Defines contracts for software communication
- Abstracts implementation details
- Enables integration between different systems
- Can be public, private, or partner APIs
- Usually documented with specifications (OpenAPI/Swagger)
- Versioned to maintain backward compatibility
Common Use Cases
- Third-party service integration (payment, maps, social)
- Mobile app backend communication
- Microservices architecture
- Data exchange between systems
- Building platform ecosystems
Example
Loading code...Frequently Asked Questions
What is the difference between an API and a Web Service?
A Web Service is a specific type of API that operates over a network using HTTP protocols. All Web Services are APIs, but not all APIs are Web Services. APIs can also include library APIs, operating system APIs, and hardware APIs that don't necessarily use HTTP.
What is API authentication?
API authentication is the process of verifying the identity of a client making an API request. Common methods include API keys (simple tokens), OAuth 2.0 (token-based authorization), JWT (JSON Web Tokens), and Basic Authentication (username/password). The choice depends on security requirements and use case.
What is API rate limiting?
API rate limiting restricts the number of API requests a client can make within a specific time period. It protects servers from being overwhelmed, ensures fair usage among clients, and prevents abuse. When limits are exceeded, APIs typically return a 429 (Too Many Requests) status code.
What is the difference between public and private APIs?
Public APIs (or Open APIs) are available to external developers and the public, often with documentation and self-service access. Private APIs are internal to an organization, used only by its own applications. Partner APIs fall in between, shared with specific business partners.
What is API versioning and why is it important?
API versioning is the practice of managing changes to an API while maintaining backward compatibility. It allows developers to introduce new features or breaking changes without disrupting existing clients. Common strategies include URL path versioning (/v1/users), query parameters, or header-based versioning.