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Code Viewer

.js, .ts, .jsx, .tsx, .py, .html, .css, .json, .xml, .yaml, .sh•100% Private (No Upload)

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v1.5.0Free · Syntax EngineDocument Tools

Free Online Code Viewer & Syntax Highlighter — JS, TS, Python, JSON

Inspect & Highlight Source Code with Line Numbers. Inspect source code files with line numbers and syntax coloring for JS, TS, Python, HTML, CSS, JSON, YAML, and Shell scripts.

What is Code Viewer and what does it do?

The Code Syntax Highlighter is a free online code viewer that opens source files with line numbers and accurate syntax coloring for JavaScript, TypeScript, Python, HTML, CSS, JSON, XML, YAML, and Shell scripts. It makes unfamiliar code fast to scan, share, and understand.

Files are parsed and highlighted locally in the browser — your proprietary scripts and configuration files never leave your machine, so it is safe even for confidential code.

  • Open .js, .ts, .jsx, .tsx, .py, .html, .css, .json, .xml, .yaml, and .sh files.
  • Detect the programming language automatically and apply the correct color theme.
  • Show line numbers for easy navigation and referencing.
  • Format and indent structured data like JSON with clean token colors.
  • Copy any file's full source to the clipboard with one click.

How does Code Viewer work?

The viewer reads the file text locally and runs a language-detection pass based on the file extension and code patterns. A syntax tokenizer then splits the source into keywords, strings, comments, and operators, painting each token with its theme color.

Line numbers are generated alongside the highlighted markup, and everything is rendered in the DOM without uploading your code anywhere. Large files stream in smoothly with virtualized rendering.

100% private: all processing happens locally in your browser using client-side WebAssembly, WebCrypto, WebAudio, and HTML5 Canvas. Your files are never uploaded to any server.

Who needs Code Viewer?

Developers reviewing code

Inspect unfamiliar scripts, config files, and diffs quickly without launching a full IDE.

Students learning to code

Read Python, JavaScript, and HTML examples with clear color coding that makes structure obvious.

DevOps & QA engineers

View YAML pipelines, shell scripts, and JSON payloads safely on any machine.

Security-conscious teams

Review private source code without pasting it into third-party web tools that store content.

Supported file formats

Code Syntax Highlighter opens and processes the following file extensions directly in your browser:

.js.ts.jsx.tsx.py.html.css.json.xml.yaml.sh

How to use Code Viewer — step by step

  1. 1

    Select Code File

    Drop any programming or data file (.js, .py, .json, .ts, etc.).

  2. 2

    Automatic Language Detection

    The syntax engine automatically detects the language and applies coloration.

  3. 3

    Inspect & Copy

    Review lines of code with numbered margins and one-click copy.

Frequently asked questions

Which programming languages are supported?

JavaScript, TypeScript, Python, HTML, CSS, JSON, XML, YAML, Shell scripts (.sh), and more.

Does it format JSON files automatically?

Yes, JSON and structured data files are formatted with clean indentation and token colors.

Is my code secure and confidential?

100% confidential. Your code never leaves your local browser memory.

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