From JSON formatters and regex testers to SQL playgrounds and AST explorers - every tool a developer reaches for daily, running entirely in the browser with no account required.

Backend developers

Format and validate JSON from API responses, decode JWTs, generate HMACs, and debug SQL queries.

Frontend developers

Test regex patterns with match highlighting, beautify HTML/CSS/JS, and preview code as screenshots for documentation.

DevOps engineers

Build and validate cron expressions, decode Unix timestamps, and convert cURL commands to code in multiple languages.

Security engineers

Generate and verify HMAC signatures, decode JWTs to inspect claims, and analyse HAR files for network requests.

Developer tools are often paywalled or ad-heavy despite being straightforward browser operations. We keep them free and private - no tracking, no data retention.

About Code Tools

Free browser-based code tools for formatting, running, exploring, and transforming code - no IDE or server required. The SQL Playground runs full SQLite in your browser via sql.js (WebAssembly), letting you create tables, write queries, and explore data without a database server. The Python Runner executes Python 3 code using Pyodide - including NumPy, Pandas basics, and standard library modules. The JavaScript Sandbox runs ES2022 code in an isolated iframe with full console output. The Code Screenshot tool turns code snippets into shareable images with syntax highlighting and custom themes. The JS Obfuscator protects client-side code. The AST Explorer visualises how parsers interpret your code - essential for writing ESLint rules and Babel plugins.

When to use Code Tools

1Testing SQL queries: write and run SQLite queries in the SQL Playground before implementing them in your application - check logic, test JOINs, and verify results.
2Quick Python scripts: run data processing, string manipulation, or algorithm experiments in the Python Runner without setting up a local environment.
3Teaching and documentation: create clean code screenshots with syntax highlighting for blog posts, README files, presentations, and social media posts.
4Writing ESLint rules or Babel plugins: use the AST Explorer to inspect the parse tree for any JavaScript or TypeScript snippet and find the exact node types to target.
5Protecting client-side JavaScript: obfuscate proprietary browser logic before deploying - making reverse engineering significantly harder.

Frequently Asked Questions

Can the Python Runner install packages with pip?+

The Python Runner uses Pyodide, which includes a curated set of packages pre-compiled to WebAssembly: NumPy, Pandas (basic), Matplotlib, scikit-learn (limited), and all Python standard library modules. You cannot install arbitrary pip packages, but the pre-loaded scientific computing packages cover most data analysis and scripting use cases.

Is the SQL Playground connected to a real database?+

No. The SQL Playground uses sql.js, a pure-JavaScript port of SQLite compiled to WebAssembly. Your database exists in memory in your browser tab and is not connected to any server. Data is lost when you close the tab unless you export it. It is ideal for learning SQL, testing queries, and prototyping schemas.

How does the JS Sandbox differ from the browser console?+

The browser console has access to your current page's DOM, cookies, and global scope. The JS Sandbox runs in an isolated iframe with no access to any page context - making it a clean environment for testing pure logic. It also supports top-level await, making async code simpler to test.

What languages does the Code Screenshot tool support?+

Over 100 languages via Prism syntax highlighting: JavaScript, TypeScript, Python, Rust, Go, Java, C/C++, Ruby, PHP, SQL, Bash, YAML, JSON, HTML, CSS, and many more. Themes include Dracula, One Dark, Nord, GitHub Light, GitHub Dark, Monokai, and Solarized.

Free Developer Tools for Formatting, Testing and Debugging Code

From JSON formatters and regex testers to SQL playgrounds and AST explorers - every tool a developer reaches for daily, running entirely in the browser with no account required.

Backend developers

Format and validate JSON from API responses, decode JWTs, generate HMACs, and debug SQL queries.

Frontend developers

Test regex patterns with match highlighting, beautify HTML/CSS/JS, and preview code as screenshots for documentation.

DevOps engineers

Build and validate cron expressions, decode Unix timestamps, and convert cURL commands to code in multiple languages.

Security engineers

Generate and verify HMAC signatures, decode JWTs to inspect claims, and analyse HAR files for network requests.

Developer tools are often paywalled or ad-heavy despite being straightforward browser operations. We keep them free and private - no tracking, no data retention.

About Code Tools

When to use Code Tools

1Testing SQL queries: write and run SQLite queries in the SQL Playground before implementing them in your application - check logic, test JOINs, and verify results.

2Quick Python scripts: run data processing, string manipulation, or algorithm experiments in the Python Runner without setting up a local environment.

3Teaching and documentation: create clean code screenshots with syntax highlighting for blog posts, README files, presentations, and social media posts.

4Writing ESLint rules or Babel plugins: use the AST Explorer to inspect the parse tree for any JavaScript or TypeScript snippet and find the exact node types to target.

5Protecting client-side JavaScript: obfuscate proprietary browser logic before deploying - making reverse engineering significantly harder.

Frequently Asked Questions

Can the Python Runner install packages with pip?+

Is the SQL Playground connected to a real database?+

How does the JS Sandbox differ from the browser console?+

What languages does the Code Screenshot tool support?+