Online API Development and Testing Tools

Access 19 professional API tools for formatting, validating, and converting data. Process requests on our secure servers with automatic file deletion.

Streamline your development workflow with our suite of 19 API tools. These utilities allow you to format JSON, validate OpenAPI specifications, and convert data structures directly from your browser. All processing is handled on Elysia Tools servers, ensuring high performance without requiring local software installation.

19 Tools

Developer & Web
API Breaking Changes Detector & Migration Planner
Compare two OpenAPI 3.x schemas, identify breaking changes, grade client impact, and suggest migration or compatibility strategies
Developer & Web
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
Developer & Web
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
Developer & Web
API Doc Generator
Generate polished API documentation from OpenAPI or annotated comments
Developer & Web
API Mock Server
Generate a runnable Redis-backed mock API server with 1-hour TTL, hot updates, and dynamic templated responses
Developer & Web
API Request Code Snippet Generator
Generate cURL and common language code snippets from a request URL, method, headers, query parameters, and body
Developer & Web
API Response Contract Validator
Validate a real API response JSON against the response schema declared in an OpenAPI 3.x specification
Developer & Web
API Response Diff & Semantic Analyzer
Compare two API response payloads, highlight field-level diffs, and classify likely functional changes versus harmless runtime drift
Data & Tables
BOM Character 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
Documents & PDF
Doc Comment to PDF Docs
Generate API documentation PDF from code comments
Data & Tables
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
Data & Tables
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
Data & Tables
JSON Key Renamer
Batch rename JSON object keys with support for patterns, rules, and transformations. Perfect for API response formatting and data normalization.
Data & Tables
JSON Path Extractor
Query JSON with JSONPath or JMESPath-style expressions, inspect matched paths, and highlight extracted values in the original document
Developer & Web
JSON Schema Generator
Infer JSON Schema from sample JSON, optionally merge manual schema edits, and validate data against the active schema
Developer & Web
JSONPath Query Tool
Query arbitrary JSON with JSONPath expressions, preview matches, switch output modes, and save reusable query templates
Developer & Web
OpenAPI Diff Breach Detector
Compare OpenAPI or GraphQL schemas, flag breaking changes, and generate an impact-oriented change report for API teams
Developer & Web
OpenAPI to TypeScript Generator
Convert OpenAPI or Swagger JSON/YAML specs into TypeScript API types, request payloads, and response models with configurable output and naming styles
Conversion & Encoding
XLSX API To Sheet
Fetch JSON from REST or GraphQL API and write mapped records into an Excel sheet with automatic pagination

Related Tags

JSON

83 Tools

Access 83 online JSON tools for formatting, validating, and converting data. Process files securely on our servers with automatic deletion after 6 hours.

OpenAPI

7 Tools

Access 7 online OpenAPI tools to validate, format, and convert API specifications. Process files securely on our servers with automatic deletion after 6 hours.

Schema

17 Tools

Access 17 online schema tools to validate, convert, and generate data structures. Process files securely on our servers with automatic deletion after 6 hours.

Data Processing

125 Tools

Access 125 online data processing tools for formatting, converting, and cleaning data. Secure server-side processing with automatic file deletion after 6 hours.

SQL

35 Tools

Access 35 online SQL tools for database management, query formatting, and data conversion. Process files securely without software installation.

Contract Testing

3 Tools

Access 3 online tools for contract testing. Validate and manage API contracts in your browser with secure server-side processing and automatic file deletion.

FAQ

How do these API tools process my data?

When you use a tool, your data is sent to Elysia Tools servers for processing. Text inputs are never stored, and any uploaded files are automatically deleted after 6 hours to maintain privacy.

Do I need to install any software to use the API utilities?

No, all tools are accessible through your web browser. You can perform complex API operations, such as schema validation or data transformation, without installing any local packages or environments.

What types of API formats are supported?

The collection includes tools for common standards like JSON, OpenAPI, and various data serialization formats, helping you debug and refine your API integrations efficiently.