Best Free API Development Tools

Proxy your API, choose which endpoints to mock in the cloud and inspect traffic, for free. Speed up your development and integration tests.

Quickly auto-generate models/class/type/interface and serializers from JSON, schema, and GraphQL for working with data quickly & safely in any programming language. Convert JSON into gorgeous, typesafe code in any language.

Proxy service for inspecting and debugging API calls. The free plan includes 10,000 requests per month.

Post HTTP Requests Online. Popular Request Methods include GET, POST, PUT, DELETE, and HEAD. Supports Headers and Token Authentication. Includes a basic login system for saving your requests.

Treblle helps teams build, ship, and govern APIs. With advanced API log aggregation, observability, docs, and debugging. You get all features for free, but there is a limit of up to 250k requests per month on the free tier.

Collaborative design API with instant API mock and generated documentation (Free for unlimited API blueprints and unlimited users with one admin account and hosted documentation). Best for unlimited usage needs.

API marketplace hosting 90+ data APIs (exchangeratesapi, ipstack, mediastack, etc.). Most APIs include a free tier with 100-1,000 requests/month. Individual API pricing varies by provider

Mockfly is a trusted development tool for API mocking and feature flag management. Quickly generate and control mock APIs with an intuitive interface. The free tier offers 500 requests per day.

Superseded: As of 2026-09-01, mocklets.com reads: Basic Free per user / month Includes: 1 Collection 10 Apis / Collection 5 Files / Collection 2 Members / Collection. We are not publishing our stored Mocklets terms beside it — our own pricing change record, discovered 2026-09-01, names them as the previous ones. Read what we recorded ↓ Note — discovered 2026-09-01: The free tier now has limits: 1 Collection, 10 Apis / Collection, 5 Files / Collection, 2 Members / Collection. Source ↗

Lightweight REST API client for VS Code and JetBrains. Free plan is $0 per user/month with local storage and 1 local collection run per month. Paid plans are billed annually from Starter at $3 per user/month, which adds JetBrains, team features, CLI and CI/CD, WebSocket/SSE/gRPC and 250 collection runs; Business is $7 and Enterprise $16.

API design, debugging, testing, and documentation platform — free tier: up to 4 users, unlimited projects, unlimited APIs, unlimited requests. API mocking included. 7-day change history Best for unlimited usage needs. Note — discovered 2026-09-10: The free tier now offers a 14-day trial instead of being perpetually free. The description of features is also more detailed, and includes limits on cloud mock server calls (10K/month). Source ↗

MockAPI is a simple tool that lets you quickly mock up APIs, generate custom data, and perform operations using a RESTful interface. MockAPI is meant to be a prototyping/testing/learning tool. One project/2 resources per project for free.

Free OSS (MIT). API development ecosystem — REST, GraphQL, WebSocket, SSE, Socket.IO, MQTT testing. Real-time collaboration, environments, collections. Web, desktop, and CLI Best for open source projects.

Superseded: As of 2026-08-28, tiny.cloud reads: The Free Plan includes 1,000 editor loads per month and TinyMCE core editing features. A 14-day free trial of 21 + advanced features is also available. We are not publishing our stored TinyMCE terms beside it — our own pricing change record, discovered 2026-08-28, names them as the previous ones. Read what we recorded ↓ Note — discovered 2026-08-28: The free plan now has a limit of 1,000 editor loads per month and includes only core editing features. A 14-day free trial of 21+ advanced features is also offered. Source ↗

Free mock REST API service providing realistic data across 9 domains (e-commerce, finance, healthcare, education, recruitment, social media, stock markets, weather, and aviation). No mandatory signup, no API keys, unlimited requests. Perfect for frontend prototyping, API testing, learning and teaching web development. Best for open source projects and students and unlimited usage needs.

Free and open-source desktop app for creating local API mocks — dynamic responses, request logging, record/replay and OpenAPI import. Mockoon Cloud adds hosted mocks and collaboration: Team is $100/month billed annually for 5 members, 3 deployed mocks and 100,000 calls/month, with a 14-day trial on a work email (7 days and a card otherwise).

API marketplace and hub — free to sign up and browse. Individual APIs set own free tiers (typically 500-1K req/mo). Platform rate limits: 1,000 req/hr, 500K req/mo. No platform fee on free API tiers

Spring Boot app generator with custom database and REST API.

Automatically generate RESTful API documentation with Swagger 2.0 for Go. Annotate your handler functions, run swag init, and get a Swagger UI endpoint; works with chi, gin, echo, fiber and net/http. Free and MIT-licensed, with optional sponsorship through Open Collective.

GraphQL federation and supergraph platform — forever free: up to 3 users, 1-day data retention, self-hosted router (60 req/min rate limit), community support. No credit card required

Hook0 is an open-source Webhooks-as-a-service (WaaS) that makes it easy for online products to provide webhooks. Dispatch up to 100 events/day with seven days of history retention for free.

API design and documentation platform — free tier: 1 user, 1 project. Includes OpenAPI visual designer, API editor, interactive docs, API console, code generation, Git sync, automatic SSL

Developer-focused PDF generation API designed with privacy in mind. It offers Stripe-inspired documentation and includes 500 free PDF conversions per month.

Superseded: As of 2026-08-28, nango.dev/pricing reads: The Free plan is $0/mo and includes 10 connections, 100k proxy requests, 10 hours of function compute time, 100k function runs, 100k custom function logs, 100k custom sync storage records, and 100k API webhooks. We are not publishing our stored Nango terms beside it — our own pricing change record, discovered 2026-08-28, names them as the previous ones. Read what we recorded ↓ Note — discovered 2026-08-28: The free tier now has specific limits on connections (10), proxy requests (100k), function compute time (10 hours), function runs (100k), custom function logs (100k), and custom sync storage (100k records). It also has limits on API webhooks (100k). Source ↗

Superseded: As of 2026-09-01, mockaroo.com reads: Mockaroo lets you generate up to 1,000 rows of realistic test data...Need more data? Plans start at just $60/year. We are not publishing our stored mockaroo terms beside it — our own pricing change record, discovered 2026-09-01, names them as the previous ones. Read what we recorded ↓ Note — discovered 2026-09-01: The free tier is limited to 1,000 rows. Source ↗

Free web-based HTTP client to send HTTP requests.

Visually create Open API 3 definitions for free.

Developer documentation platform — custom domain, web editor, API playground, custom components, LLM optimizations. For individuals

Get instant access to over 120+ APIs for free, built with quality, consistency, and reliability in mind. The free plan covers up to 50 API Tokens per month. (Possibly taken down, 2025-06-25) Best for open source projects.

Suite of 15 REST APIs (IP geolocation, email validation, screenshots, exchange rates, phone validation, etc.) — free tier: 1,000 requests/month per API, 1 request/second rate limit. Non-commercial use only on free tier

Create a fake REST API from a JSON object, and customize HTTP status codes, headers, and response bodies.

No-code, cloud-based platform for mocking and debugging multi-protocol APIs (REST, SOAP, gRPC & GraphQL), providing instant servers with rules-based logic, CRUD & stateful mocking, proxying, and CORS management for faster integration and testing. The free plan includes 50 requests per day and provides a public dashboard/endpoint where anyone with the dashboard URL can view submitted requests and responses.

Create a free endpoint to which you can send HTTP requests. Any HTTP requests sent to that endpoint will be recorded with the associated payload and headers so you can observe recommendations from webhooks and other services.

GraphQL API for Amazon.com product, search, and category data. The free plan includes 100 calls per month.

Create secure RESTful APIs from CSV files. Upload a CSV file and instantly access the data via its API allowing faster application development. The free plan includes 2 APIs and 2,500 API calls per month. You don't need a credit card.

Free OSS (MIT). Git-based offline API client — REST, GraphQL, collections stored as files in your repo. No cloud, no accounts, no sync. Desktop app for Mac/Linux/Windows. The #1 open-source Postman alternative Best for open source projects.

Open-source API client for designing and testing REST, GraphQL, gRPC, WebSocket, and SSE APIs. Local-first with Git sync and optional cloud storage. No account required for local testing. Desktop app for Mac/Linux/Windows. Free tier includes unlimited projects and collection runner Best for unlimited usage needs.

Free gRPC GUI client to call and test gRPC APIs. Can import gRPC APIs via server reflection.