Smart Web Apps Guide
Developer tools

Developer tools guide

These tools help you convert, validate, and debug common formats quickly. They’re designed for real-world workflows: copy/paste a snippet, get a clear result, then copy the output back into your editor.

Before you start (important)
  • Everything runs locally in your browser (no account required). Still, avoid pasting secrets if you don’t trust your device or extensions.
  • Base64 is reversible (encoding), not encryption.
  • URL encoding is context-specific: encoding a full URL is different from encoding a query parameter.
  • Regex flags (g, i, m, etc.) can change results dramatically.

Quick workflows (copy/paste friendly)

Debug an API response
  1. Paste into JSON Formatter.
  2. Fix parse errors, then pretty-print.
  3. Copy formatted JSON back to your editor.
Fix a broken URL query
  1. Paste into URL Encoder/Decoder.
  2. Decode to inspect, adjust values, then encode again.
  3. Test in your browser or client.
Validate a snippet quickly
  1. Paste into JavaScript Syntax Validator.
  2. Get the exact line context for syntax errors.
  3. Copy the report into a bug ticket.
Convert timestamps for logs
  1. Use Unix Timestamp Converter.
  2. Compare UTC vs local time for incident timelines.
  3. Convert back to epoch for API requests.

What each tool is for (with practical examples)

JSON Formatter

Use this to validate, pretty print, and minify JSON. It’s especially useful when a config file or API response fails to parse and you need a readable error.

Example
{
  "user": {"id": 7, "name": "Noel",},
}
Trailing commas are valid in some JavaScript contexts, but not valid JSON. Formatters make these errors obvious.
Open JSON Formatter

Base64 Converter

Base64 converts binary data into text so it can be safely transported (for example in JSON, HTML, or email). It is not secure by itself.

Example
Input:  hello
Base64: aGVsbG8=
Round-trip check: encode → decode should return exactly the original text (including whitespace).
Open Base64 Converter

URL Encoder/Decoder

URLs use reserved characters. If you put raw text into a query string, it can break parsing. Encode parameters before sending them, and decode when debugging.

Example
Text:  fish & chips
Encoded: fish%20%26%20chips
Tip: prefer encoding the component value, not the entire URL, unless you know what you’re doing.
Open URL Encoder/Decoder

Regex Tester

Use this to test patterns, see matches, and verify flags. The two most common “why didn’t it match?” causes are missing flags and incorrect escaping.

Example
Pattern:  \\b\\d{4}-\\d{2}-\\d{2}\\b
Matches:  2026-03-19
Tip: if you’re copying from code, remember that many languages double-escape backslashes inside strings.
Open Regex Tester

JavaScript Syntax Validator

This tool checks whether code is syntactically valid JavaScript and returns a clear error report with line context. It performs a parse-only check and does not execute the code you paste.

Open JavaScript Syntax Validator

More developer utilities (when you need them)

UUID Generator

Generate UUID v4 values in bulk for test data and IDs.

Open UUID Generator
Number Base Converter

Convert between binary, decimal, hexadecimal, and more (helpful for debugging).

Open Base Converter
iFrame Generator

Generate embed code with sensible safety options (sandboxing, referrer policy).

Open iFrame Generator
Lorem Ipsum Generator

Generate placeholder text by words, sentences, or paragraphs.

Open Lorem Ipsum

Troubleshooting

  • “Valid” but still broken: a syntax check doesn’t catch runtime errors. Use your browser console and unit tests.
  • Different results than your app: environments differ (Node vs browser, locale/timezone, regex engine, etc.).
  • Copy/paste issues: invisible whitespace can change outputs. Try trimming or showing characters in your editor.
Related
Security tools guide Hash Generator