Best Free API Development Tools

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. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-15, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-15, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

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. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-02, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-02, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

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. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-02, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-02, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

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. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-10, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-10, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

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. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-13, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-13, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

Proxy your API, choose which endpoints to mock in the cloud and inspect traffic, for free. Speed up your development and integration tests. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-02, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-02, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

Create a fake REST API from a JSON object, and customize HTTP status codes, headers, and response bodies. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-02, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-02, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

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. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-02, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-02, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

Developer-focused PDF generation API designed with privacy in mind. It offers Stripe-inspired documentation and includes 500 free PDF conversions per month. We could not read the page we cite for this offer when we last looked, on 2026-09-12, so we cannot confirm these terms today.

• −1 stale_verification We cannot confirm this offer: 1 consecutive re-check attempt has failed (most recently 2026-09-12 — HTTP 403), never confirmed since it was indexed. This is our inability to verify, not a change by the vendor. (a limit of ours, not a change by the vendor)

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. We could not read the page we cite for this offer when we last looked, on 2026-09-10, so we cannot confirm these terms today.

• −1 stale_verification We cannot confirm this offer: 2 consecutive re-check attempts have failed (most recently 2026-09-10 — page content too short (likely JS-rendered SPA); the rendering client failed: the rendering client did not finish in time), never confirmed since it was indexed. This is our inability to verify, not a change by the vendor. (a limit of ours, not a change by the vendor)

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. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-02, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-02, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

Visually create Open API 3 definitions for free. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-02, so we cannot confirm these terms today.

• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-02, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

Proxy service for inspecting and debugging API calls. The free plan includes 10,000 requests per month. We could not read the page we cite for this offer when we last looked, on 2026-09-10, so we cannot confirm these terms today.

• −1 stale_verification We cannot confirm this offer: 2 consecutive re-check attempts have failed (most recently 2026-09-10 — page content too short (likely JS-rendered SPA); a rendering client read 476 characters), never confirmed since it was indexed. This is our inability to verify, not a change by the vendor. (a limit of ours, not a change by the vendor)

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. The page we cite for this offer states no amount, tier or rate we can read when we last looked, on 2026-09-02, so we cannot confirm these terms today. Note — 2026-10-31: Apiary reaches end of life on 2026-10-31, when Oracle stops the service and deletes remaining instances. Oracle announced it on 2025-10-28. The Free plan is the only one still open, so it ends with the product. Source ↗

• −3 free_tier_withdrawn Recorded product deprecation on 2026-10-31: Apiary reaches end of life on 2026-10-31, when Oracle stops the service and deletes remaining instances. Oracle announced it on 2025-10-28. The Free plan is the only one still open, so it ends with the product. Source: https://docs.oracle.com/en-us/iaas/Content/servicechanges.htm#oracle-apiary
• −1 stale_verification Our last read of the vendor's pricing page, on 2026-09-02, could read no amount, tier or rate on the page. This is our confidence in the record, not a change by the vendor. (a limit of ours, not a change by the vendor)

API design and documentation platform (SmartBear) — no permanent free tier. Swagger's own pricing FAQ, read 2026-09-05: "You can get started with Swagger with a free trial, no credit card required, then choose the plan that best fits your usage and requirements." The same FAQ puts the free Swagger tools on the open-source side — Swagger Editor, Swagger UI and Swagger Codegen, run locally — and SwaggerHub among the commercial products. Plan prices are client-rendered and were not read. Note — discovered 2026-04-13: Free community plan replaced by trial only Source ↗

• −3 free_tier_withdrawn Recorded free tier removal on 2026-04-13: Free community plan replaced by trial only Source: https://swagger.io/product/pricing/
• −2 time_limited_offer Tier "Trial" is a trial that expires, not an ongoing free tier.