Developer Utilities

1. Select the developer operation and paste its expected input.
2. Check the language, format or validation options.
3. Run the operation and review diagnostics or exported code.

Limits and requirements

Generated code and validation results still need review in your own environment.

Check each operation’s notes. Some workflows run on your device; others use the OneTabTool server or a named third-party service. Don’t assume every tool processes files in the same way.

Available operations

• URL parser & query inspector
• HTTP header parser
• ASCII / Unicode character table
• Unix permission calculator
• HTTP status code reference
• Email syntax & domain validator

  Optional DNS lookup sends only the domain to Google DNS. It cannot confirm mailbox existence or deliverability. Supports practical ASCII addresses and internationalized domains; quoted local parts are not supported.

• Placeholder text generator
• ULID generator
• Cron parser & next runs
• Cron expression builder
• Language detector

  Statistical language guesses, not confidence percentages.

• Markdown table generator
• HTML live preview

  Preview is sandboxed; scripts and external navigation are disabled.

• JavaScript minifier
• GraphQL formatter / syntax validator
• JSON Schema validator
• Mermaid diagram generator
• CSS selector specificity

  Supports selector lists, :is(), :where(), :not(), :has(), nth-child of selectors and shadow selectors. Expand & nesting with its parent before calculation.

• CSS → Tailwind arbitrary utilities

  Creates arbitrary-property utilities for Tailwind 4. Paste declarations only; selectors, at-rules and dynamic template fragments need manual handling.

• Regex structure explainer

  Token reference only; not a full semantic explanation of nested expressions.

• cURL → JavaScript / Python

  Parses common request/header/data flags. Never executes the request.

• GraphQL schema → TypeScript
• Phone number parser

  Format validation cannot confirm ownership or whether a number is active.

• Encryption key & parameter inspector

  Checks symmetric key length, encoding, obvious repetition and IV/nonce length. Cannot certify cryptographic strength or randomness from a pasted key.

• Random numeric OTP

  Random code only. Delivery, expiry, attempt limits and verification belong on your server.

Questions about Developer Utilities