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A free, open-source Chrome DevTools extension for testing APIs — capture, inspect, edit, and replay HTTP requests without an external proxy, plus a quick header and secrets audit.
FreeOpen source
What to know▼
How it works
A Chrome DevTools extension that captures, inspects, edits, and replays HTTP/HTTPS requests without an external proxy, plus a Quick Security Check that audits headers and flags secrets or PII.
What's different
Works without needing to route traffic through an external proxy, unlike typical API testing setups.
Pricing
Free and open-source.
Best for
Developers testing API security directly inside Chrome DevTools.
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An open-source SDK that unifies multiple payment providers (Paystack, Flutterwave, Razorpay, Monnify, Interswitch) behind one API, instead of integrating each provider separately across web, mobile, and no-code platforms.
FreeOpen source
What to know▼
How it works
Native SDKs for React, Vue, Svelte, React Native, Flutter, iOS, Android, plus no-code plugins for Shopify, WordPress, Webflow, Wix, Squarespace.
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Bundles auth, payments and a database into one integration for indie hackers building digital products, instead of wiring together separate services and fragile webhooks yourself.
Watch out · Currently limited to 100 early-adopter developer signups rather than being generally available.
Free
What to know▼
How it works
Bundles authentication, payments and a database into one system for indie hackers launching digital products, integrated with a single command instead of stitching together separate services and webhook logic. An AI agent handles the setup, and billing, access and customer data stay in sync automatically.
What's different
Positioned as 'Stripe for indie hackers' — one integration instead of assembling auth, payments and a database from separate tools.
Pricing
Free for the first 100 early-adopter developers who sign up.
Best for
Indie hackers building and launching digital products who want backend infrastructure handled for them.
Watch out
Currently limited to 100 early-adopter developer signups rather than being generally available.
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A REST API and TypeScript SDK for NYC real-estate data — listings, building records, price history — with a free no-key tier and a hosted MCP server for AI agents.
Free
What to know▼
How it works
A REST API and TypeScript SDK for NYC real estate data — rental and sale listings, building records, neighborhood boundaries, price history and market snapshots, returned as JSON. Also ships a hosted MCP server so AI agents can query listings directly, plus signed webhooks, SSE streaming and OAuth.
What's different
Fills a gap where no official public API exists for NYC real estate listings.
Pricing
Free tier needs no API key for search, areas and market tools; paid plans add full listing/building detail, faster data freshness and higher limits.
Best for
Developers building applications or AI agents that need structured NYC real estate data.
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A unified API gateway for testing multiple LLMs like Qwen and GLM through one OpenAI-compatible key, for developers who don't want to wire up separate provider APIs.
Free
What to know▼
How it works
OpenAI SDK-compatible endpoint with auto-fallback on upstream errors
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Turns a single HTTP POST request into a push notification on your phone, for developers wanting alerts from CI, cron jobs, or webhooks without building an app.
Free
What to know▼
How it works
Send a POST request with a publish key and it's delivered as a push notification via topics
What's different
No SDK or account setup needed to send an alert
Pricing
Free to receive notifications
Best for
Developers wanting alerts from scripts, CI, or webhooks
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Free browser-based PDF and photo editing tools (edit, compress, convert, OCR) that never upload files, for privacy-conscious users avoiding paid software or sign-ups.
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Validates Tax ID numbers against country-specific rules for all 249 countries, showing exactly which checks passed or failed rather than a plain valid/invalid.
Free
What to know▼
How it works
Checks length, structure, checksum, and format rules per country via web UI or REST API
What's different
Shows rule-level detail instead of just valid/invalid
Best for
Developers and compliance teams validating TINs before they enter a system
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Bundles five small free-tier developer APIs (WHOIS, company lookup, email validation, geolocation, sanctions screening) as a cheaper alternative to separate paid subscriptions.
Watch out · Built with Cursor AI; open source on GitHub.
FreeOpen source
What to know▼
How it works
Bundles five production APIs: Domain WHOIS via RDAP, Company Info from Wikipedia/Wikidata, Email Validator with MX+SMTP, IP Geolocation with dual-source fallback, and a Sanctions Screener with 20K+ OFAC/UN entities.
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A curated GitHub list of 50+ free AI API providers for developers who want LLM access without paying — a reference directory, not a product that offers its own API.
Free
What to know▼
How it works
A curated GitHub list documenting over 50 free AI API providers, compiled for developers who want LLM access without paying.
Pricing
Lists free-tier AI API providers.
Best for
Developers building hackathon projects or learning to code who want zero-cost LLM API access.
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A free, open-source CLI and web tool that turns an OpenAPI spec into a ready-to-use client SDK in TypeScript, Python, Go, Dart or Java — a developer tool, not an API service.
FreeNo sign-upOpen source
What to know▼
How it works
Turns an OpenAPI spec into a production-ready SDK in TypeScript, Python, Go, Dart or Java, with a code preview, ZIP download, a CLI (npx sdkcraft), API change detection, and an AI documentation generator.
What's different
Free, open source and requires no signup.
Pricing
Free and open source.
Best for
Developers who need a client SDK generated from an existing OpenAPI spec instead of writing one by hand.
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A free API returning real-time air quality data (AQI, PM2.5, PM10) with strong coverage of Indian cities, plus an endpoint suggesting the best time window to go outside.
Free
What to know▼
How it works
Single API call returns AQI/PM2.5/PM10 and a safe/caution/avoid verdict
What's different
Better Indian city coverage than typical global AQI APIs
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Adds a pay-per-use paywall settled in USDC to your API, MCP server or Shopify/WooCommerce store so AI agents can pay you directly, keeping all the revenue, no card needed to start.
Free
What to know▼
How it works
Adds an agent-ready paywall to your API, MCP server, or Shopify/WooCommerce store with one line of code or a plugin; AI agents pay in USDC, settled in about 2 seconds, and every paid listing appears on the Loomal Index for agent discovery.
What's different
You keep 100% of revenue — no percentage cut, ever.
Pricing
Free to start, no card required; flat monthly plans as you grow. Launch offer: first 500 sellers get 1,000 transactions free.
Best for
Developers monetizing APIs, MCP servers or online stores for AI-agent buyers.
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A desktop HTTP testing and automation tool for developers, with request chaining, OpenAPI support and cURL generation. Runs fully offline, free, with no ads or subscription.
FreeWorks offlineNo subscription
What to know▼
How it works
A desktop HTTP testing environment for creating, automating and validating HTTP workflows, with OpenAPI support, request chaining, dynamic parameters, advanced response validation, and cURL generation.
What's different
Completely free and offline, with no ads, subscriptions, or feature restrictions, plus native ARM support.
Pricing
Free, with no ads, subscriptions, or feature restrictions.
Best for
Developers building and validating HTTP request workflows and APIs.
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A free, keyless MCP database of verified step-by-step fixes and documented failure modes (like Stripe webhooks breaking) that AI agents can query before attempting a task.
Free
What to know▼
How it works
An MCP server that AI agents query before attempting a task; it returns verified 'routes' — step sequences plus documented failure modes (e.g. express.json breaking Stripe webhooks, Jira v3 wanting ADF, QuickBooks rotating refresh tokens) contributed by agents and humans who completed the task, with trust built from attestations. One MCP install works with Claude, OpenAI, LangChain, and CrewAI.
What's different
Reads are free and keyless, and it publishes 8,700+ routes across 2,100+ domains with live metrics.
Pricing
Reads are free and keyless.
Best for
Developers running AI agents that repeatedly hit the same known integration failures and want documented fixes up front.
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Spins up a disposable URL to inspect incoming webhook payloads, plus an MCP endpoint so a coding agent like Claude Code or Cursor can read captures and help debug.
FreeNo sign-up
What to know▼
How it works
Creates disposable webhook URLs to capture and inspect incoming payloads; requests can be viewed live, replayed, or forwarded to localhost.
What's different
MCP endpoint lets a coding agent like Claude Code or Cursor read captured payloads directly and help debug the failing webhook.
Pricing
Free forever.
Best for
Developers debugging webhook integrations who want no sign-up and no setup.
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A developer-facing REST API for real-time and historical currency and forex rates across 1000+ currencies — built for businesses and developers, not individual consumers.
Free
What to know▼
How it works
A REST API delivering real-time and historical exchange rates and currency conversion across 1022+ currencies, returning JSON or XML responses for integration into other applications.
Pricing
Free tier available.
Best for
Developers and fintech platforms that need to integrate live or historical currency data into their own applications.
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A free IP geolocation API returning country, city, ASN, timezone and threat signals for any IP address, with 50 free requests per minute across several data formats.
Free
What to know▼
How it works
An IP geolocation API returning country, city, ASN, timezone and threat signals for any IP address, available in JSON, XML, CSV and PHP formats.
Pricing
Free tier offers roughly 2 million requests per month at 50 requests per minute.
Best for
Developers who need IP geolocation or threat data in their app without paying for a commercial API tier.
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A free transactional email-sending API and SMTP toolkit for developers to plug into their own apps.
Free
What to know▼
How it works
A free email-sending API and SMTP toolkit for developers to send emails, test SMTP configurations, and integrate email features into their applications.
Pricing
Free.
Best for
Developers who need to add transactional email sending to their own apps.
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A screenshot API that turns any URL or HTML into a PNG, JPEG or PDF in one request, with a JSON-driven template mode for social share images. Built for developers; free for the first 200 screenshots a month.
Free
What to know▼
How it works
A single API call (curl + API key) turns any URL or HTML into a pixel-perfect PNG, JPEG or PDF screenshot; a JSON-plus-template mode also generates OG social share images without needing HTML/CSS skills.
What's different
No SDK or complex setup required, and screenshots run on a managed Chromium pool with no cold starts or timeouts.
Pricing
Free during beta — 200 screenshots per month, no credit card required.
Best for
Developers who need a screenshot or OG-image API without managing their own rendering infrastructure.
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Routes each API prompt to the cheapest model that can handle it, cutting AI API costs — a developer tool for teams with real LLM spend, with a free tier.
Free
What to know▼
How it works
Routes each API prompt through a single endpoint to the cheapest model capable of handling it, cutting AI API costs by 30-80%.
Pricing
Free tier included.
Best for
Developer teams with real LLM API spend looking to cut costs without changing their integration.
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A free authentication and software-licensing API with HWID locking and reseller support, for developers building native C++, C# or ImGui apps who need to license their software.
Free
What to know▼
How it works
An authentication and software-licensing API with HWID locking for native C++, C# and ImGui applications, including reseller features.
Pricing
Free.
Best for
Developers who need to license and hardware-lock native applications.
