API & Networking
Browse our free API & Networking collection for developers. Every tool works in your browser with no installation required.
29 tools
HTTP Header Parser
Parse HTTP headers
Swagger / OpenAPI Viewer
Visualize and explore OpenAPI 3.x and Swagger 2.0 specs instantly
Mini Postman (API Tester)
Test REST APIs directly in your browser — no install needed
Internet Speed Test
Check download speed, latency, jitter, and upload availability from your browser
Mixpanel Toolkit
Local Mixpanel event sandbox
cURL to Code Converter
Convert HTTP requests across cURL, code, HAR, and structured formats with local secret protection.
Local Port Scanner
Automatically find localhost development servers
Dev Service Status
Check GitHub, OpenAI, Claude, Vercel, Cloudflare, npm and other developer services in one place.
HAR to Markdown
Compile sanitized network logs for backend debugging and AI agents
HAR to OpenAPI
Generate a reviewable OpenAPI contract from sanitized browser traffic
User Agent Parser
Parse any User-Agent string into browser, OS, device, and bot details
Query Params ⇄ JSON Converter
Convert URL query strings to JSON and JSON back to query strings, with repeated keys and Unicode intact
HAR File Viewer
Inspect HAR network logs as a waterfall or table, with secrets masked
OpenAPI Diff & Breaking Change Checker
Compare two OpenAPI or Swagger specs and flag breaking API changes
CORS Tester & Policy Analyzer
Test CORS in your browser or simulate a preflight with any Origin
Cache-Control Analyzer & Builder
Explain Cache-Control headers for browsers and CDNs, then build one from TTLs
GraphQL API Tester
Send GraphQL queries and mutations, then inspect the response, errors and schema
WebSocket & SSE Tester
Connect to WebSocket and Server-Sent Events endpoints from your browser and inspect every message live.
API Mock Server
Mock REST API routes with rules, delays, scenarios and a temporary public endpoint
CIDR / Subnet Calculator
IPv4 and IPv6 subnet math, address types and subnet splitting
MIME Type Lookup
Find the MIME type for any file extension, with IANA status and Content-Type snippets
TCP / UDP Port Lookup
Look up any port for its official IANA assignment and common developer uses
IPv4 Address Converter
Convert IPv4 between dotted, integer, hex and binary forms
IPv4 Range & CIDR Calculator
Convert IPv4 ranges to the minimal CIDR list, list their addresses, or expand a CIDR block
IPv6 Parser
Expand, compress and inspect any IPv6 address
IPv6 ULA Generator
Random RFC 4193 unique local /48 prefixes with /64 subnets
MAC Address Vendor Lookup
Find the vendor behind a MAC address and decode its address bits
TLS Endpoint Inspector
Check TLS 1.0 to 1.3 support, cipher, ALPN and the served certificate for one public host
URL Parser
Inspect URL components and ordered query parameters locally.
