Best Free Developer Tools and Utilities
Free developer tools for API testing, debugging, and productivity.
Aider
An AI pair programming tool that runs in the terminal, edits your local files directly, and commits changes to git — supporting every major LLM provider including local models.
Appsmith
Open-source low-code platform for building internal tools and admin panels — a self-hostable alternative to Retool.
Atuin
Replaces your shell history with a searchable, encrypted, syncable database — search by directory, exit code, or full text across every machine.
Bruno
An open-source API client that stores collections as plain-text files in your repository, designed as a privacy-focused alternative to Postman.
Bun
A fast all-in-one JavaScript runtime, package manager, bundler, and test runner — designed as a drop-in replacement for Node.js with dramatically faster startup times and install speeds.
Bundlephobia
Find the cost of adding any npm package to your bundle — size, download time, and composition breakdown.
Can I Use
A compatibility table showing browser support for HTML, CSS, JavaScript, and SVG features across all major browsers and versions.
Carbon
Create and share beautiful images of source code in seconds.
Chroma
An open-source vector database that runs in-process with no server required, designed specifically for AI applications that need to store and retrieve embeddings alongside metadata.
Code Beautify
Format, validate, and beautify JSON, XML, CSS, SQL, and dozens of other code and data formats instantly in your browser.
CodePen
An online code editor and social platform for front-end developers to build, share, and discover HTML, CSS, and JavaScript snippets in an instant live-preview environment.
Cody
An AI coding assistant developed by Sourcegraph that lives in your IDE and understands your entire codebase to help write and fix code.
Continue
An open-source AI code assistant extension for VS Code and JetBrains that connects to any LLM — including local models through Ollama — for autocomplete, inline edits, and chat.
Coolify
An open-source, self-hostable platform-as-a-service for deploying applications, databases, and services on your own servers with a Heroku-like experience.
CrewAI
An open-source multi-agent framework for orchestrating teams of specialized AI agents that collaborate on complex tasks, with role assignment, task delegation, and sequential or parallel execution.
Crontab Guru
Visual editor and validator for cron schedule expressions with human-readable descriptions.
CyberChef
The local-first digital Swiss Army knife for analyzing, converting, and transforming data formats through simple drag-and-drop recipes.
DB Browser for SQLite
A simple, focused GUI for creating, browsing, and editing SQLite database files — the format used by Django, mobile apps, and embedded systems.
DBeaver
Universal database GUI supporting PostgreSQL, MySQL, SQLite, MongoDB, Redis, and 80+ others with a SQL editor, ER diagrams, and data export.
Deno
A modern JavaScript and TypeScript runtime with built-in security, native TypeScript support, a standard library, and first-class support for web platform APIs — with a formatter, linter, and test runner included.
Devdocs.io
Unified API documentation browser with instant search across 500+ docs.
DSPy
A Stanford-developed framework for algorithmically optimizing LLM prompts and pipelines, replacing hand-written prompts with compiled programs that automatically improve based on defined metrics.
Explain Shell
Paste any shell command and get a visual breakdown of every flag and argument with documentation.
Gitignore.io
Generate .gitignore files for any combination of operating systems, IDEs, and programming languages.
Grep.app
Search across public GitHub repositories for exact code patterns instantly.
GTmetrix
Website performance analysis tool that grades pages against Google Core Web Vitals and Lighthouse metrics with detailed waterfall request charts.
Hoppscotch
Open-source API development ecosystem that runs entirely in your browser.
H SuperTools AI Online Web SEO Tools
HSuperTools offers a comprehensive suite of SEO & web AI tools, image converters, editors, and productivity enhancers designed to make your life easier.
htmx
A small JavaScript library that extends HTML with attributes for making AJAX requests, WebSocket connections, and CSS transitions directly in markup — enabling dynamic interfaces without writing JavaScript.
HTTPie
A command-line HTTP client designed to be human-readable — colorized, formatted output and a much simpler syntax than raw curl.
Hurl
Runs HTTP requests defined in plain-text files from the command line, with JUnit and HTML reports for chaining requests in CI pipelines.
IT Tools
A collection of handy browser-based utilities for developers and IT professionals — encoding, formatting, generation, conversion, and network tools in one place.
JSONCrack
Visualizes JSON, YAML, XML, and CSV data as interactive node graphs for easier exploration.
JSON Formatter
Paste in messy JSON and instantly get it formatted, validated, and readable — a quick utility for developers debugging API responses.
JWT.io
Decodes and verifies JSON Web Tokens in the browser, showing the header, payload, and signature verification status.
k6
An open-source load testing tool that uses JavaScript scripts to define virtual user scenarios, with output compatible with Prometheus and Grafana and support for HTTP, WebSockets, and gRPC.
Keycloak
Open-source identity and access management — single sign-on, social login, and user federation as a self-hostable alternative to Auth0.
LangFuse
An open-source LLM engineering platform for tracing, evaluating, and monitoring AI applications in production, with prompt versioning, A/B testing, and user feedback collection.
LangGraph
A low-level framework from LangChain for building stateful, multi-agent AI applications as explicit graphs, with controllable execution flow, human-in-the-loop support, and built-in persistence.
llama.cpp
A high-performance C++ inference engine for running large language models on CPU and GPU with minimal dependencies, supporting quantized GGUF models for consumer hardware.
LLaMA-Factory
A unified fine-tuning framework supporting 100+ language models with a web UI and CLI, covering SFT, RLHF, DPO, and other training methods with efficient LoRA and QLoRA support.
LocalStack
A local cloud emulator that runs AWS services — S3, Lambda, DynamoDB, SQS, API Gateway, and dozens more — inside Docker, enabling fully local development and testing without AWS credentials or costs.
Medusa
Open-source, headless commerce framework — build a fully custom online store backend as a free, self-hostable alternative to Shopify.
Mermaid Live Editor
Write flowcharts, sequence diagrams, and ER diagrams in plain text and see them render live — exportable as SVG or PNG.
mitmproxy
An open-source interactive HTTPS proxy for intercepting, inspecting, modifying, and replaying HTTP and HTTPS traffic from any application — desktop, mobile, CLI, or IoT device.
MXToolbox
A suite of free network diagnostic tools focused on email infrastructure — MX record lookup, SPF/DKIM/DMARC testing, blacklist checking, and SMTP diagnostics.
n8n
Fair-code workflow automation platform — visually connect apps and APIs like Zapier, but self-hostable with no per-task pricing.
Neon
A serverless PostgreSQL platform that separates storage from compute — enabling instant database branching, autoscaling to zero when idle, and per-second billing with full Postgres compatibility.
ngrok
A reverse proxy that creates a secure tunnel from a public HTTPS URL to your localhost, exposing local servers for webhooks, OAuth callbacks, mobile app testing, and sharing demos with clients.
Observable
Reactive JavaScript notebooks for data visualization and analysis.
OpenHands
An open-source autonomous AI software engineering agent that can write code, run terminal commands, browse the web, and interact with your codebase to complete multi-step programming tasks.
OpenRouter
A unified API gateway that routes requests to dozens of large language models through a single endpoint and API key.
OpenSEO
Open-source, self-hosted alternative to Semrush and Ahrefs — keyword research, rank tracking, backlinks, and site audits you host yourself.
OverAPI
Massive cheat sheet collection covering keyboard shortcuts and APIs for dozens of languages and tools.
pgvector
A PostgreSQL extension that adds vector similarity search to your existing database, letting you store embeddings and run nearest-neighbor queries alongside regular SQL queries.
Playwright
Microsoft's end-to-end testing framework that controls Chromium, Firefox, and WebKit with a single API — with auto-waiting, network interception, parallel test execution, and a visual trace debugger.
PocketBase
Open-source backend in a single Go binary with database, auth, and file storage.
Postman
The most widely used API client — build, test, and document requests with collections, environments, and automated test scripts.
Promptfoo
An open-source tool for testing, evaluating, and comparing LLM prompts and models through automated test suites, red-teaming, and side-by-side output comparison.
PublicWWW
Search engine for source code snippets across millions of live websites.
PydanticAI
An agent framework built by the Pydantic team that brings type safety and structured validation to LLM applications, ensuring model outputs conform to defined schemas at runtime.
Qdrant
A high-performance open-source vector search engine written in Rust, designed for production AI applications with support for filtering, payload storage, and sparse-dense hybrid search.
Quicktype
Paste JSON and instantly get type-safe models in TypeScript, Python, Go, Rust, and 20+ more.
RAGFlow
An open-source RAG engine with deep document understanding — extracts structured content from PDFs, presentations, spreadsheets, and images using OCR and layout analysis before chunking.
Railway
Deploy a database, backend, or full app straight from a GitHub repo with almost no configuration — Postgres, Redis, Node, Python, and more.
Ray.so
Create beautiful code screenshots with syntax highlighting and customizable themes.
Regex101
Real-time regex tester with explanation, debugger, and community library.
RegExr
Interactive regex tester with real-time match highlighting, a community pattern library, and detailed explanation of each pattern element.
Render
Cloud hosting platform with zero-config deploys for static sites and web services, plus a genuinely usable free tier.
Requestly
Browser-level HTTP interception and mocking tool — redirect requests, modify headers, and mock API responses without setting up a proxy.
Security Headers
Free HTTP security header scanner that grades websites and explains what each missing header protects against — actionable before deployment.
Shlink
Open-source, self-hosted URL shortener with a full REST API — a free alternative to Bitly for link shortening and click tracking.
Shodan
The search engine for internet-connected devices — discover exposed servers, webcams, industrial systems, and IoT hardware visible on the public internet.
SigNoz
Open-source observability platform — metrics, traces, and logs in one dashboard as a self-hostable alternative to Datadog.
SmallDev.tools
Lightweight collection of developer utilities for formatting, encoding, diffing, and generating data — all client-side with no ads or cookie banners.
Smee
A webhook payload delivery service that exposes a public URL and forwards incoming webhook events to your localhost development server in real time — no account, no setup, no configuration.
Smolagents
Hugging Face's minimalist agent library where agents write and execute Python code as their primary reasoning tool, rather than calling predefined function schemas.
Squoosh
Browser-based image compression tool from Google that supports WebP, AVIF, and advanced codec options.
SSL Labs
Free SSL/TLS configuration testing tool that grades your server security and identifies vulnerabilities.
StackBlitz
A browser-based IDE that runs Node.js projects entirely in the browser using WebContainers, with npm install, hot reload, and shareable URLs.
Supabase
Open-source Firebase alternative — Postgres database, authentication, storage, and realtime subscriptions bundled into one backend platform.
Tauri
A framework for building lightweight desktop applications using web technologies with a Rust backend — producing native binaries a fraction the size of Electron apps by using the OS WebView instead of bundling Chromium.
Textise
Renders any webpage as plain text, stripping CSS, JavaScript, and ads.
tldr pages
Community-maintained command-line cheat sheets that show practical examples instead of exhaustive manual pages.
Transform Tools
Collection of code transformation utilities — convert JSON to TypeScript, SVG to JSX, CSS to Tailwind, and more.
Turso
A SQLite-based database platform for edge and serverless deployments — consistent SQLite semantics with replication, branching, and a global edge network accessible via HTTP from any environment.
Umami
Simple, open-source, privacy-focused website analytics — a self-hosted, cookie-free alternative to Google Analytics.
Unsloth
A fine-tuning library that makes QLoRA and LoRA training 2x faster and use 50% less memory than standard implementations, enabling fine-tuning of large models on consumer GPUs.
URLScan.io
A free service that scans URLs and renders them in an isolated browser, capturing all network requests, DOM structure, and screenshots for security analysis.
Vaultwarden
Lightweight, unofficial self-hosted server compatible with Bitwarden clients — run your own password manager backend instead of paying for 1Password.
vLLM
A high-throughput production inference engine for large language models using PagedAttention memory management, capable of serving dozens of concurrent users from a single GPU.
Wappalyzer
Technology profiler that identifies the frameworks, CMS, analytics, and infrastructure used by any website — as a browser extension or web lookup.
Warp Terminal
Modern AI-augmented terminal with collaborative features and intelligent command search.
Webhook.site
Instantly generate a unique URL to inspect, test, and debug webhooks and HTTP requests.
WebPageTest
A free web performance testing tool that runs your site from real browsers in real locations, producing detailed waterfall charts, Core Web Vitals, and optimization recommendations.
Zellij
Terminal workspace and multiplexer with persistent, reusable layouts — split panes, tabs, and sessions that survive a disconnect.
Zod
A TypeScript-first schema declaration and validation library that infers static types from runtime schemas — eliminating the need to maintain both a TypeScript type and a separate runtime validator.