EsyTool

Free Developer Tools Online

Browser-based utilities for everyday development tasks. No installs, no sign-up — open a tool and start working immediately.

JSON Formatter

Format, validate, and minify JSON data instantly.

UUID Generator

Generate random UUIDs (v4) quickly.

Base64 Encoder/Decoder

Encode or decode strings to Base64 format.

Hash Generator

Generate SHA-1, SHA-256, SHA-384, and SHA-512 hashes from any text.

URL Encoder/Decoder

Encode or decode URLs and query strings using percent-encoding.

Timestamp Converter

Convert Unix timestamps to human-readable dates and vice versa.

Number Base Converter

Convert numbers between decimal, binary, octal, and hexadecimal.

JWT Decoder

Decode and inspect JSON Web Tokens — header, payload, and expiry.

CSS Minifier

Remove comments and whitespace from CSS to reduce file size.

JS Minifier

Strip comments and collapse whitespace from JavaScript.

HTML Viewer

Preview and format HTML code live in a sandboxed browser.

Regex Tester

Test and debug regular expressions client-side.

SQL Formatter

Format and beautify SQL queries client-side.

JSON Validator

Validate and find errors in JSON files client-side.

Markdown Previewer

Write and preview Markdown formatting live.

XML Formatter

Format and indent XML files client-side.

YAML Formatter

Format and lint YAML files client-side.

Cron Expression Generator

Generate and explain cron job schedules client-side.

Diff Checker

Compare two text blocks and highlight differences.

Essential Browser-Based Developer Utilities for Everyday Engineering Tasks

Modern software development involves constant switching between data formats, encodings, tokens, and debugging utilities. Developers need to validate JSON from an API response, decode a JWT to check its expiry, generate a UUID for a database record, or minify CSS before a deploy — often multiple times per hour. Installing dedicated desktop apps for each of these tasks is impractical and adds unnecessary friction to workflows.

EsyTool's developer utilities run entirely in your browser. There is no installation, no account, and — critically — no data leaves your machine. This is especially important when working with JWTs that contain user claims, production API payloads, or hashed credentials. Everything stays local.

Why Client-Side Matters for Developer Tools

Many popular online developer utilities send your input to a backend for processing. For a JSON formatter, this may seem harmless. But consider these scenarios:

  • JWT tokens contain base64-encoded user data, session claims, and authentication information. Pasting a real JWT into a third-party service is a significant security risk.
  • Hash generators used with real passwords allow a malicious service to log plaintext-to-hash mappings for dictionary attacks.
  • API response bodies may contain PII, internal schema information, or business-sensitive data that should never leave your network.
  • SQL queries can reveal database structure, table names, and logic that constitute intellectual property.

Client-side processing eliminates all of these risks. The computation happens inside your browser's JavaScript engine — no server ever sees your input.

Overview of Developer Utilities

JSON Formatter & Validator

Beautify or minify JSON with syntax highlighting and precise error location reporting. Paste raw API responses to instantly identify malformed fields.

JWT Decoder

Decode the header, payload, and signature of any JSON Web Token. View claims, expiry time, and issuer without sending the token to any server.

Base64 Encoder / Decoder

Encode text or binary files to Base64, or decode Base64 strings back to readable text. Supports URL-safe Base64 variants.

Hash Generator

Generate MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes from any text input using the browser's native Web Crypto API.

CSS & JS Minifier

Strip comments, collapse whitespace, and minify CSS or JavaScript files before deployment. Reduce bundle sizes to improve page load performance.

Diff Checker

Compare two text blocks side by side with character-level and line-level diff highlighting. Essential for reviewing config changes, migration scripts, or code reviews.

Best Practices for Developer Workflows

  1. Always validate JSON before deploying: A single missing comma or mismatched bracket in a configuration file can cause production outages. Run JSON through the validator as a final check before deployment.
  2. Check JWT expiry before debugging auth issues: The most common cause of unexpected 401 errors is an expired JWT. Decode the token first to check the exp claim before diving deeper.
  3. Use SHA-256 or higher for security-sensitive hashing: MD5 and SHA-1 are cryptographically broken for security purposes. Use them only for checksums. For anything security-related, use SHA-256 or SHA-512.
  4. Minify CSS and JS in CI/CD, not manually: Manual minification is a last resort. Use the minifier to spot-check file size reductions, then integrate a proper bundler (Vite, webpack, esbuild) into your build pipeline.

Frequently Asked Questions

Is it safe to decode a production JWT in these tools?

Yes — EsyTool's JWT Decoder runs entirely in your browser. The token is decoded using JavaScript's built-in atob() and JSON parsing — no network request is made. Your token is never transmitted anywhere.

Which regex flavours does the Regex Tester support?

The Regex Tester uses JavaScript's native RegExp engine, which supports all standard ES2023 regex features including named capture groups, lookaheads, lookbehinds, Unicode property escapes, and the d flag for indices.

Can I format SQL from multiple database engines?

Yes. The SQL Formatter supports MySQL, PostgreSQL, Microsoft T-SQL, and SQLite dialects. Select the target dialect from the dropdown to apply engine-specific keyword formatting and indentation rules.