API Basics

What is an API?

API stands for Application Programming Interface. An API is an intermediary that allows two applications to interact with each other. It works like a messenger between two parties, where one party requests and receives a response from another party for the request.

Who is a Client?

A client is a software distributed to customers who can access or communicate with the server by using an API. This could be an internal service or an external facing asset like a mobile app (Android/iOS) or mobile website or website.

What is a Server?

A server is a machine running some processes that will process some service for you based on a user's request via API.

What are Status Codes?

Status codes are sent by a server in response to the request made by a client.

Response status codes are distributed into five categories -

  • 1xx: Informational
  • 2xx: Success
  • 3xx: Redirection
  • 4xx: Client Error
  • 5xx: Server Error

1xx: Informational

Status Code

Meaning

100

Continue

101

Switching Protocols

102

Processing

103

Early Hits

2xx: Success

Status Code

Meaning

200

OK

201

Created

202

Accepted

203

Non-Authoritative Information

204

No Content

205

Reset content

206

Partial Consent

207

Multi-Status

208

Already Reported

226

IM Used

3xx: Redirection

Status Code

Meaning

300

Multiple Choice

301

Moved Permanently

302

Found

303

See Other

304

Not Modified

305

User Proxy

306

Unused

307

Temporary Redirect

308

Permanent Redirect

4xx: Client Error

Status Code

Meaning

400

Bad Request

401

Unauthorized

402

Payment required

403

Forbidden

404

Not Found

405

Method Not Allowed

406

Not Acceptable

407

Proxy Authentication Required

408

Request Timeout

409

Conflict

410

Gone

411

Length Required

412

Precondition Failed

413

Payload Too Large

414

URI Too Long

415

Unsupported Media Type

416

Range Not Satisfiable

417

Expectation Failed

418

I'm a Teapot

421

Misdirect Request

422

Unprocessable Entity

423

Locked

424

Failed Dependency

425

Too Early

426

Upgrade Required

428

Precondition Required

429

Too Many Requests

431

Request Header Fields Too Large

451

Unavailable for Legal Reasons

5xx: Server Error

Status Code

Meaning

500

Internal Server Error

501

Not Implemented

502

Bad Gateway

503

Service Unavailable

504

Gateway Timeout

505

HTTP Version Not Supported

511

Network Authentication Required


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