Top 10 Online Developer Tools Every Programmer Needs in 2025

Modern development requires constant data transformation, validation, and encoding. Instead of switching between dozens of websites and CLI tools, here are the 10 tools that cover 90% of daily developer tasks — all available free on ConvertTOON.

1. JSON Formatter & Validator

The most-used developer tool. Paste minified JSON, get beautifully formatted output with proper indentation. Catch syntax errors instantly with clear error messages.

→ Try JSON Formatter | → Try JSON Validator

2. JSON ↔ YAML Converter

Kubernetes configs, Docker Compose files, CI/CD pipelines — YAML is everywhere. Quickly convert between JSON and YAML without installing any CLI tools.

→ Try JSON to YAML

3. JWT Token Decoder

Debug authentication issues by inspecting JWT token headers and payloads. No need to use jwt.io — decode tokens right in your browser without sending them to any server.

→ Try JWT Decoder

4. Base64 Encoder/Decoder

Encode and decode Base64 strings instantly. Essential for working with APIs, image data, and encoded payloads.

→ Try Base64 Tool

5. Code Generator (JSON → TypeScript/Python/Java/Go/C#)

Paste a JSON API response and instantly get type definitions in your language of choice. Supports TypeScript interfaces, Python dataclasses, Java POJOs, Go structs, and C# classes.

→ Read the full guide

6. Cron Expression Parser

Stop guessing what 0 */4 * * 1-5 means. Paste any cron expression and get a human-readable description with next scheduled run times.

→ Try Cron Parser

7. SHA-256 Hash Generator

Generate cryptographic hashes for data integrity verification, checksums, and security purposes. Supports SHA-256 and SHA-1.

→ Try Hash Generator

8. UUID Generator

Generate random UUID v4 or timestamp-based UUIDs in bulk. Copy individual IDs or generate hundreds at once for testing.

→ Try UUID Generator

9. JSON Fixer

Got broken JSON from a log file or API response? The JSON Fixer automatically repairs common issues: trailing commas, missing quotes, single quotes, and more.

→ Try JSON Fixer

10. Data Format Optimizer (JSON → TOON)

The flagship tool. Convert JSON to TOON format for 30-50% size reduction. Perfect for optimizing LLM API costs, reducing bandwidth, and improving performance.

→ Try ConvertTOON

Why Browser-Based Tools Matter

• Privacy: Your data never leaves your device
• Speed: No server round-trips, instant results
• Accessibility: Works on any device with a browser
• No setup: No npm install, no pip install, no downloads