6.1 HTTP & APIs
Every entry filed under HTTP & APIs and its subtopics.
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Works on
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- Beginner
- You are new to this topic.
- Intermediate
- You use it, and want to get better.
- Advanced
- You know it well and need the details.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
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- Numbered steps to get one task done.
- Cheat sheet
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- Fixes an error
- An error message, what it means, and how to solve it.
25 entries
- 0411 CORS explained, and how to fix the browser error The browser blocks a request from one origin to another unless the server allows it with Access-Control headers. Fix it in the… Intermediate · Step by step · Any system, Browser Article Making requests · Web servers & reverse proxies 15 Oct 2026
- 0414 HTTP headers you should set on every site The response headers that make a site safer and faster: HSTS, Content-Security-Policy, X-Content-Type-Options, frame protection, Referrer-Policy, Permissions-Policy and Cache-Control, with Nginx and… Intermediate · Cheat sheet · Any system Article Making requests · Web servers & reverse proxies 15 Oct 2026
- 0415 Check a site’s TLS expiry and security headers from the terminal A bash script that connects to a domain, prints the certificate's issuer and expiry with days remaining, and reports which recommended security… Intermediate · Step by step · Linux, macOS Script Making requests · Web servers & reverse proxies 15 Oct 2026
- 0325 Fix: SSL certificate problem: unable to get local issuer certificate curl, git, pip or npm cannot chain the server's certificate to a root they trust. Usual causes: a corporate proxy that re-signs… Intermediate · Fixes an error · Linux, macOS, Windows Article Common errors · Making requests · TLS & certificates 15 Oct 2026
- 0305 What is a token? A token is a string that proves who you are or what you may do, sent with requests instead of a password. Beginner · Explains an idea · Any system Article Authentication 15 Oct 2026
- 0300 What is a REST API? A REST API is a web API where you use normal HTTP requests on URLs to read, create, update and delete things. Beginner · Explains an idea · Any system Article Making requests 15 Oct 2026
- 0301 What is HTTP? HTTP is the request and response language that browsers, apps and servers use to exchange web pages and data. Beginner · Explains an idea · Any system Article Making requests 15 Oct 2026
- 0303 What is CORS? CORS is a browser rule that decides whether a web page from one site is allowed to call an API on another… Beginner · Explains an idea · Any system Article Making requests 15 Oct 2026
- 0302 What is a status code? A status code is the three digit number a web server returns to say whether a request worked, like 200 OK or… Beginner · Explains an idea · Any system Article Status codes 15 Oct 2026
- 0304 What is a cookie? A cookie is a small piece of text a website stores in your browser so it can recognise you on the next… Beginner · Explains an idea · Any system Article Authentication 15 Oct 2026
- 0267 What is an API? An API is a set of rules that lets one program ask another program for data or actions without knowing how it… Beginner · Explains an idea · Any system Article Making requests 15 Oct 2026
- 0263 Build a notes REST API with plain Node.js: CRUD, validation, status codes and CORS Write a small JSON API for notes using only Node.js built-ins: create, read, update and delete, input validation, correct HTTP status codes,… Intermediate · Guided project · Any system Article Making requests · Node.js · Status codes 15 Oct 2026
- 0088 Fix: Access to fetch at ‘…’ from origin ‘…’ has been blocked by CORS policy The browser refused to give your script a cross-origin response because the server did not send the right Access-Control-* headers. Fix it… Intermediate · Fixes an error · Browser Article Common errors · Making requests 15 Oct 2026
- 0094 curl and libcurl (curl/curl) The source of curl, the command-line tool for transferring data with URLs, and libcurl, the C library behind it that many other… Any system Repo Making requests 15 Oct 2026
- 0081 How an HTTP request works: methods, headers, and body An HTTP request is a short text message a client sends to a server: a method and path, some headers, and sometimes… Beginner · Explains an idea · Any system Article Making requests 15 Oct 2026
- 0082 HTTP status codes: the common ones and what to do A quick reference to the HTTP status codes you will meet most often, what each one means, and the first thing to… Beginner · Cheat sheet · Any system Article References · Status codes 15 Oct 2026
- 0083 Test a JSON API with curl A runnable bash script showing the curl commands you need most when testing an API: GET, POST JSON, custom headers, Bearer tokens,… Beginner · Step by step · Linux, macOS, Windows Script Authentication · Making requests 15 Oct 2026
- 0089 Fix: 413 Request Entity Too Large A server or proxy rejected your request because its body is bigger than the configured limit. Find which layer set the limit,… Intermediate · Fixes an error · Any system, Linux Article Status codes · Web frameworks 15 Oct 2026
- 0084 Tiny JSON echo server for testing HTTP clients A standard-library Python server that echoes back the method, path, query, headers, and body of every request, and can return any status… Intermediate · Step by step · Any system Script Files & automation · Making requests 15 Oct 2026
- 0085 fetch with timeout, retries, and exponential backoff A drop-in fetch wrapper that times out slow requests, retries network errors and 429/5xx responses with jittered exponential backoff, and honors Retry-After. Advanced · Step by step · Any system, Browser Script Async code · Making requests 15 Oct 2026
- 0086 API authentication basics: API keys, Bearer tokens, and OAuth How APIs know who is calling: static API keys, Bearer tokens in the Authorization header, Basic auth, and a high-level tour of… Intermediate · Explains an idea · Any system Article Authentication 15 Oct 2026
- 0087 CORS explained: why the browser blocks your request CORS is the browser rule that decides whether JavaScript on one origin may read a response from another. The server opts in… Intermediate · Explains an idea · Browser Article Async code · Making requests 15 Oct 2026
- 0012 Requests: HTTP for humans Requests is the classic Python library for calling web APIs and downloading pages, with a simple API for GET and POST requests,… Any system Repo Files & automation · Making requests 15 Oct 2026
- 0019 fetch with timeout, retries and proper error handling A reusable fetchJson helper for Node 20+ and browsers that adds a timeout, retries with backoff for temporary failures, and clear errors… Intermediate · Step by step · Any system Script Async code · Making requests 15 Oct 2026
- 0030 Axios A promise-based HTTP client for browsers and Node.js with interceptors, automatic JSON handling, request cancellation and a consistent API in both environments. Any system Repo Async code · Making requests 15 Oct 2026