# API

Browse 35 online API tools for processing, converting, validating, and managing API data in your browser.

> Canonical page: https://elysiatools.com/en/tags/api

## Overview

Use this collection of 35 API tools to process, convert, validate, and manage API data through a browser-based interface. No software installation is needed.

## Frequently asked questions

### What can I do with API tools?

You can process, convert, validate, and manage API data using the tools in this collection.

### Do I need to install software to use these API tools?

No. You can operate the tools through your browser without installing software.

### How is my data handled?

Your requests are submitted from the browser and processed on Elysia Tools servers. Text inputs are not stored, and uploaded files are automatically deleted after 6 hours.

## Tools

- [API Breaking Changes Detector & Migration Planner](https://elysiatools.com/en/tools/api-breaking-changes-detector-migration-planner): Compare two OpenAPI 3.x schemas, identify breaking changes, grade client impact, and suggest migration or compatibility strategies
- [API Contract Mutation Tester](https://elysiatools.com/en/tools/api-contract-mutation-tester): Mutate OpenAPI request fields into semantically risky variants and optionally send them to a real backend to check defensive validation coverage
- [API Contract Stress Tester](https://elysiatools.com/en/tools/api-contract-stress-tester): Generate boundary-value test cases from an OpenAPI 3.x document and optionally send them to a real backend to spot contract mismatches
- [API Doc Generator](https://elysiatools.com/en/tools/api-doc-generator): Generate polished API documentation from OpenAPI or annotated comments
- [API Latency Budget Planner](https://elysiatools.com/en/tools/api-latency-budget-planner): Plan and visualise an API latency budget. Enter a P99 target (e.g. ≤ 300ms) and per-stage allocations (DNS, TCP, TLS, TTFB, Processing, Network) to see a live waterfall, budget utilisation, and over-budget warnings. Optionally paste an OpenTelemetry or Datadog trace to reverse-engineer a measured allocation.
- [API Mock Server](https://elysiatools.com/en/tools/api-mock-server): Generate a runnable Redis-backed mock API server with 1-hour TTL, hot updates, and dynamic templated responses
- [API Request Code Snippet Generator](https://elysiatools.com/en/tools/api-request-code-snippet-generator): Generate cURL and common language code snippets from a request URL, method, headers, query parameters, and body
- [API Response Contract Validator](https://elysiatools.com/en/tools/api-response-contract-validator): Validate a real API response JSON against the response schema declared in an OpenAPI 3.x specification
- [API Response Diff & Semantic Analyzer](https://elysiatools.com/en/tools/api-response-diff-semantic-analyzer): Compare two API response payloads, highlight field-level diffs, and classify likely functional changes versus harmless runtime drift
- [cURL to Go (net/http) Converter](https://elysiatools.com/en/tools/curl-to-go): Convert a cURL command into a Go net/http code snippet with http.NewRequest, headers, and body
- [cURL Command to HAR Converter](https://elysiatools.com/en/tools/curl-to-har-converter): Convert a cURL command into a portable HAR 1.2 request entry.
- [cURL to JavaScript (axios) Converter](https://elysiatools.com/en/tools/curl-to-js-axios): Convert a cURL command into a JavaScript axios code snippet with config object, headers, and data
- [cURL to JavaScript (fetch) Converter](https://elysiatools.com/en/tools/curl-to-js-fetch): Convert a cURL command into a JavaScript fetch() code snippet with headers, body, and method
- [cURL to PHP (cURL) Converter](https://elysiatools.com/en/tools/curl-to-php): Convert a cURL command into a PHP cURL code snippet with curl_setopt, headers, and post fields
- [cURL to Python (requests) Converter](https://elysiatools.com/en/tools/curl-to-python): Convert a cURL command into a Python requests code snippet with headers, data, and method
- [Currency Exchange Calculator](https://elysiatools.com/en/tools/currency-exchange): Convert an amount between currencies using live exchange rates from a free, no-key API (open.er-api.com). Supports 160+ world currencies. Shows the converted amount, the exchange rate used, a comparison table against popular currencies, and the rate update timestamp.
- [BOM Character Remover](https://elysiatools.com/en/tools/data-bom-remover): Remove BOM (Byte Order Mark) characters from text and file content. Perfect for cleaning up text files that have encoding issues, fixing CSV imports, and preparing data for processing. Features: - Detect and remove UTF-8 BOM (EF BB BF) - Detect and remove UTF-16 BOM (FE FF or FF FE) - Detect and remove UTF-32 BOM (00 00 FE FF or FF FE 00 00) - Support multiple input formats - Visual BOM character display - Detailed detection report - Support for batch text processing Common Use Cases: - Fix CSV file import errors - Clean up text file encoding issues - Prepare data for JSON parsing - Fix XML parsing problems - Resolve API data encoding conflicts - Standardize text data format
- [Doc Comment to PDF Docs](https://elysiatools.com/en/tools/doc-comment-to-pdf-docs): Generate API documentation PDF from code comments
- [Env File Secret Rotation Planner](https://elysiatools.com/en/tools/env-file-secret-rotation-planner): Paste a .env file and get a staged secret-rotation plan. Detects database URLs, API keys, auth tokens, private keys, cloud credentials, payment keys and encryption secrets, scores each by exposure and age, and schedules them across a 4-week rotation timeline with a dual-key checklist and a generated .env.example. Optional last-rotated dates and a configurable cadence (30/90/180/365 days) drive compliance scoring.
- [GraphQL Playground](https://elysiatools.com/en/tools/graphql-playground): An in-browser GraphQL client: write queries and variables, send them to any GraphQL endpoint, and inspect formatted JSON results or error arrays — perfect for iterating on schemas during development
- [Header Adder](https://elysiatools.com/en/tools/header-adder): Add headers to CSV data that lacks column names. Perfect for data import from databases, API responses, or numeric datasets that need proper column identification. Features: - Add custom headers to header-less data - Auto-generate intelligent headers - Support for various header naming conventions - Preview headers before applying - Multiple header format options - Support for existing data detection - Batch processing capabilities Common Use Cases: - Fix database exports without headers - Process API response data - Prepare numeric datasets for analysis - Standardize data column naming - Create proper CSV structures - Data format normalization
- [Header Remover](https://elysiatools.com/en/tools/header-remover): Remove headers from CSV data to create clean header-less files. Perfect for database imports, data processing pipelines, API integrations, and systems that require header-less CSV format. Features: - Remove first row (header) from CSV data - Remove multiple header rows - Skip empty lines before removing headers - Preserve data integrity - Support various CSV separators - Preview before removal - Data validation options - Batch processing capabilities Common Use Cases: - Prepare data for database imports - Clean up API response data - Remove metadata from exported files - Create header-less data for machine learning - Prepare data for systems that don't use headers - Extract pure data values from structured files
- [HMAC Generator & Verifier](https://elysiatools.com/en/tools/hmac-generator-verifier): Compute an HMAC message-authentication signature over a message + shared secret using SHA-1/SHA-2/SHA-3/BLAKE2, or verify an incoming signature against the secret — with webhook presets for Stripe / Slack / GitHub and constant-time comparison
- [HTTP Request Tester](https://elysiatools.com/en/tools/http-request-tester): A lightweight in-browser HTTP client (mini Postman): send GET/POST/PUT/DELETE requests with custom headers and body, inspect status, headers, timing, and formatted response — all from your browser

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