API

The most widely used library for turning JSON into objects and back in Java. in Java & JVM →

A framework that starts Spring applications running with no configuration burden. in Java & JVM →

The application framework that dominates enterprise Java — dependency injection, web, data. in Java & JVM →

A directory gathering the docs and console of hundreds of public APIs in one place. in Backend, API & System Design →

An hour-long backend introduction working through resource naming, versioning and error-format decisions with their reasoning. in Backend, API & System Design →

A resource list for Directus, the headless CMS offering a real-time API and dashboard. in Backend, API & System Design →

A list of plugins, examples and tutorials for FastAPI, Python’s fast web framework. in Backend, API & System Design →

Derives validation and an OpenAPI schema from type hints, and a working test UI appears at /docs by itself. in Backend, API & System Design →

A directory of over three hundred free public APIs, each carrying a liveness status and a last-checked date. in Backend, API & System Design →

The client declares which fields it wants, so over- and under-fetching are solved at the schema level. in Backend, API & System Design →

A readable alternative to curl that sends HTTP requests with coloured JSON output and a simple syntax. in Backend, API & System Design →

Turns a web page into an API — you point at the page and it works out the rest. in Backend, API & System Design →

A maintained fork of Public APIs, born while the original went untended. in Backend, API & System Design →

A categorised list of free APIs with auth type, HTTPS and CORS support marked in the table. in Backend, API & System Design →

Event-driven library for bidirectional real-time communication between browser and server; adds automatic reconnection… in Backend, API & System Design →

Payment infrastructure whose documentation is an industry benchmark — test cards, webhook retry logic and idempotency… in Backend, API & System Design →

An OpenAPI toolset to design, document and try RESTful APIs. in Backend, API & System Design →

Hands you a URL instantly and shows every request that arrives, headers included. in Backend, API & System Design →

Realtime database, auth, storage and hosting in one package. in Databases →

A RESTful API built to improve your API automation testing. in Testing & QA →

A series of challenges, tutorials and references for practising API testing, by Alan Richardson (EvilTester). in Testing & QA →

An automation practice site with a UI, an API backend and a ready list of test cases. in Testing & QA →

Spins up a mock REST endpoint in seconds and intercepts or fakes HTTP requests. in Testing & QA →

A simple public GraphQL API serving country, continent and language data, with no key required. in Testing & QA →

A fake JSON REST API offering dozens of resources for quick prototyping and test data. in Testing & QA →

A fake e-commerce REST API with products, carts and users for front-end prototypes. in Testing & QA →

A test API with OAuth2 authentication and write support, over REST and GraphQL. in Testing & QA →

An HTTP testing service that echoes headers, body and response. in Testing & QA →

A clean API client for REST, GraphQL and gRPC requests. in Testing & QA →

A zero-setup test API that returns realistic fake JSON on request. in Testing & QA →

An email sandbox that captures outgoing mail before it reaches real recipients. in Testing & QA →

An API serving movie and series data, handy for tests and prototypes. in Testing & QA →

A large, deeply nested REST API serving Pokémon data — popular for tests and tutorials. in Testing & QA →

A desktop/cloud tool to build, store as collections and test API requests. in Testing & QA →

A realistic tool-shop demo with both a UI and a REST API, designed for end-to-end testing. in Testing & QA →

An API generating any number of fake users (name, address, photo). in Testing & QA →

A hosted REST API that answers AJAX requests, with pagination and delay simulation. in Testing & QA →

A test API emulating room booking, with authentication and good docs. in Testing & QA →

A free API serving character, episode and location data over both REST and GraphQL. in Testing & QA →

A REST API simulating a virtual store, for teaching API testing. in Testing & QA →

The canonical sample API with a Swagger UI front end — the standard place to learn OpenAPI. in Testing & QA →

A sample REST API filled with Star Wars data. in Testing & QA →

An API serving cat images and data — a fun one for prototypes and tests. in Testing & QA →

Claude model versions, context limits and token pricing. in AI · Models & Assistants →

Rather than compete on chat, it sits on the retrieval side: its Rerank model reorders candidates returned by vector… in AI · Models & Assistants →

Developer gateway for the Gemini API and the open-weight Gemma family. in AI · Models & Assistants →

A browser surface for testing prompts, setting system instructions and fiddling with temperature. in AI · Models & Assistants →

An LLM inference service delivering very high tokens per second on its own LPU hardware. in AI · Models & Assistants →

A Europe-based model provider. Compared with US providers it operates under EU data rules, and ships small models under… in AI · Models & Assistants →

Parameter reference for the Chat Completions, Responses and Realtime endpoints. in AI · Models & Assistants →

API keys, rate limits and billing, with organisation-level quota settings and usage graphs. in AI · Models & Assistants →

One endpoint reaching many LLMs, routing by price and availability across providers. in AI · Models & Assistants →

Lets you run open machine-learning models through a single API. in AI · Models & Assistants →

Serves open-weight large language models with fast hosted inference. in AI · Models & Assistants →

Curated directory of LLM API providers offering free tiers or trial credits, complete with rate limits and model lists… in AI · Agents & Infrastructure →

OpenAI models with Azure’s region selection and private networking. in AI · Agents & Infrastructure →

Ships ready tool definitions and delegated OAuth for a thousand-odd apps. in AI · Agents & Infrastructure →

Compresses tool output, logs and RAG chunks before they reach the model, running as a library, a proxy or an MCP server. in AI · Agents & Infrastructure →

An LLM observability tool: change the base URL and requests are logged as they pass through. in AI · Agents & Infrastructure →

An API focused on prompt injection and jailbreak detection. in AI · Agents & Infrastructure →

An open protocol over JSON-RPC for exposing tools and data sources to models. in AI · Agents & Infrastructure →

Routes one OpenAI-compatible endpoint to hundreds of providers, many with free tiers. in AI · Agents & Infrastructure →

CLI agent that inspects browser network captures (HAR files) and turns undocumented web API calls into reusable Python… in AI · Agents & Infrastructure →

Represents 100+ languages in one vector space, so a Turkish query can retrieve an English document. in AI · RAG, Embeddings & Vectors →

Reference for the text-embedding-3 family — dimensions, pricing, usage. in AI · RAG, Embeddings & Vectors →

Embedding models trained separately for law, code and finance; it joined MongoDB in 2025. in AI · RAG, Embeddings & Vectors →

An open-source vector database. Unlike databases that only store vectors, it can host embedding generation as a module… in AI · RAG, Embeddings & Vectors →

A self-hostable machine translation API running Argos Translate models. in AI · Applied Tools →

A natural-language service for developers that turns text and speech into intents and entities. in AI · Applied Tools →

Single-purpose background removal with an API and batch mode, so it drops into a pipeline. in AI · Generative Media →

A Google-backed project that merges statistics from the Census, WHO, the UN and dozens of other sources into one… in Data Science & ML →

NASA’s portal to its satellite and Earth-observation data, from rainfall and ice cover to vegetation and the atmosphere. in Data Science & ML →

The US national archive of weather, climate, ocean and geophysical data, formerly NCDC. in Data Science & ML →

A free, open-source weather API that needs no key for non-commercial use. in Data Science & ML →

One of the largest open databases of companies, merging national company registers into one search. in Data Science & ML →

X-lab's analysis platform publishing open-source health metrics derived from GitHub activity (OpenRank, activity, contributors). in Data Science & ML →

End-to-end computer vision platform for image annotation, dataset augmentation, public dataset sharing, and YOLO… in Data Science & ML →

The World Health Organization’s country-level health indicators: causes of death, vaccination, health spending, risk factors. in Data Science & ML →

A service that bridges websites, the fediverse (Mastodon etc.) and Bluesky/AT Protocol so accounts can follow and reply across networks. in Networking & Sysadmin →

RIPE NCC's network of thousands of small probes that run ping, traceroute and DNS measurements from around the world. in Networking & Sysadmin →

An RSS reader where you decide what you read at the source level, unlike algorithmic feeds — and nothing you have not read disappears. in Self-Hosting & Personal Cloud →

A live IOC feed that collects malicious URLs, domains, IPs and hashes shared by the infosec community on Twitter/X, served as CSV/JSON/RSS/API. in Offence, Defence & OSINT →

A scanning service that opens a URL in a real browser and records every request the page makes, the domains it contacts, a screenshot and the DOM. in Offence, Defence & OSINT →

An open catalogue of scholarly works, authors, institutions and journals; all the data is CC0 and queryable through a free API. in Science & Academia →

The official US publisher of GDP, national accounts, personal income and international trade data. in Economics →

The official US source for employment, unemployment, wages and consumer inflation (CPI). in Economics →

The Turkish central bank’s time-series store: exchange rates, interest rates, money supply, balance of payments and the market participants survey. in Economics →

Official OECD statistics across member economies, standardised for cross-country comparison straight from the source. in Economics →

Gathers macro indicators — GDP, inflation, rates — for 196 countries in one dashboard with historical series and forecasts. in Economics →

The UN database of countries’ merchandise trade by product (HS code) and partner. in Economics →

The official publisher of US population, household, housing and business statistics, home to the American Community Survey and the economic censuses. in Economics →

A developer guide and reference for building on Bitcoin: transactions, RPC and the P2P network. in Finance, Markets & Crypto →

A library giving one API over more than a hundred crypto exchanges (JavaScript, Python, PHP and others). in Finance, Markets & Crypto →

Crypto prices and market-cap rankings, with the data also available through a free API. in Finance, Markets & Crypto →

Market data for thousands of crypto assets, DEXes included, with a free API. in Finance, Markets & Crypto →

Widely used crypto prices and rankings by market cap. in Finance, Markets & Crypto →

An analytics platform where the community builds dashboards with SQL queries over blockchain data. in Finance, Markets & Crypto →

Ethereum’s canonical block explorer, with transaction tracing, contract verification and an API. in Finance, Markets & Crypto →

A service aggregating financial and economic data from many sources under one API (formerly Quandl). in Finance, Markets & Crypto →

A service returning placeholder photos at any size (the lorem ipsum of images). in Icons, Photos & Illustration →

A book covering GraphQL from both client and server side. in Free Books & Long Reads →

Tests an API’s CORS headers from the outside. in Converters, Formatters & Checkers →

A collection of developer tools: a REST client, a SQLite browser, XML and JSON validators, regex testing. in Converters, Formatters & Checkers →