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Developer Tools

Best Free Online Tools for Developers

A curated list of the most useful free online tools for developers, covering JSON, API testing, code formatting, security, and network utilities.

Published September 25, 2024

Developers use dozens of small tools throughout the day. Having them available in the browser, without installing software, saves time and keeps your workflow smooth. This guide covers the most useful free online tools for developers, organized by category, with tips on when to use each one.

JSON tools

JSON is the most common data format in modern development, and working with it efficiently requires the right tools. A JSON formatter beautifies minified JSON for readability. A validator checks syntax and pinpoints errors. A tree viewer helps navigate large nested structures. A diff tool compares two JSON documents. A converter transforms JSON to CSV, YAML, or TypeScript types.

JSON Toolkit at json.explorme.com combines all of these functions in a single, browser-based workspace. It processes data client-side, which is important when working with sensitive API responses or configuration files that contain secrets.

API testing tools

An API tester lets you send HTTP requests and inspect responses without writing code or installing a desktop application. You can test GET, POST, PUT, PATCH, and DELETE requests, set custom headers, send request bodies, and view the response status, headers, and body. This is essential for debugging API integrations, testing webhook endpoints, and verifying request formats.

Look for a tool that supports all HTTP methods, lets you save common requests, and displays responses with syntax highlighting. ToolKit at toolkit.explorme.com includes an API tester alongside 53 other developer and productivity tools.

Code formatting and conversion

Code formatters clean up inconsistent indentation, spacing, and line breaks in code snippets. They are useful when you paste code from different sources or when you need to standardize formatting before sharing. Look for formatters that support multiple languages and let you configure the formatting style.

Conversion tools transform code between formats. A cURL-to-code converter takes a cURL command and generates equivalent code in JavaScript, Python, Go, and other languages. This saves time when integrating API calls into your application. A JSON-to-TypeScript converter generates type interfaces from JSON samples.

Security tools

Security tools help developers work with cryptographic operations and authentication tokens. A password generator creates strong, random passwords with configurable length and character sets. A hash calculator computes MD5, SHA-1, SHA-256, and other hashes from text input. A JWT decoder reads the header and payload of a JSON Web Token without the signature verification, which is useful for debugging authentication flows.

When using security tools, always verify that they process data client-side. Passwords, tokens, and sensitive text should never be transmitted to a server. ToolKit includes password generation, hash calculation, and JWT decoding, all running in the browser.

Network tools

Network tools help developers diagnose connectivity and DNS issues. A DNS lookup tool queries DNS records for a domain, including A, AAAA, MX, TXT, CNAME, and NS records. An IP information tool shows details about an IP address. An HTTP headers tool displays the response headers from a URL, which is useful for debugging CORS, caching, and security header issues.

These tools require external network requests by their nature, but the tool itself should not store your queries. ToolKit includes DNS and IP tools alongside its other utilities.

Text and encoding tools

Text tools handle common string operations: case conversion (camelCase, snake_case, kebab-case, title case), find and replace, slug generation, word and character counting, and text diffing. Encoding tools handle base64 encoding and decoding, URL encoding and decoding, and HTML entity encoding.

These tools are simple but frequently needed. Having them in one place saves the time of searching for a separate tool for each operation. ToolKit includes all of these text and encoding tools in its collection of 54 utilities.

How to choose the right tool

When choosing developer tools, prioritize three factors: privacy, speed, and integration. Privacy means the tool processes data client-side whenever possible, especially for sensitive input like API keys and tokens. Speed means the tool loads quickly and responds instantly. Integration means the tool is part of a collection so you do not need to switch between different sites for related tasks.

A command palette, favorites, and recently used features help you work faster by reducing the time spent navigating to the tool you need. ToolKit at toolkit.explorme.com offers all of these features in a single, fast interface.

Common mistakes to avoid

  • Using server-side tools for sensitive data. Always check whether a tool processes data client-side before pasting API keys, tokens, or production data.
  • Switching between many different tool sites. A collection of tools in one place saves time and reduces context switching.
  • Ignoring keyboard shortcuts. A command palette lets you jump to any tool instantly without navigating menus.
  • Using outdated tools that do not support modern formats like WebP or modern JSON features. Choose tools that are actively maintained.
  • Forgetting to verify tool results. Hash calculators, JWT decoders, and API testers should be cross-checked when the results matter.

FAQ

ToolKit

54 daily-use tools across 9 categories

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JSON Toolkit

Format, validate, diff, convert, and query JSON in the browser

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Explorme Tunnel

A self-hostable ngrok alternative for exposing localhost

Learn more

Looking for more tools? Explore our Developer Tools category.