DevLab Developer Tools Guide

15+ free browser-based developer utilities — JSON, JWT, regex, cron, Base64, UUID and more. No signup, no data sent to servers.

All Tools at a Glance

• JSON Formatter / Validator — Pretty-print and validate JSON. Shows errors with line numbers.
• JSON ↔ CSV Converter — Convert JSON arrays to CSV spreadsheet format and back.
• SQL Formatter — Formats and indents SQL queries for readability.
• JWT Decoder — Decodes and displays JWT header, payload and expiry. No signature verification.
• Cron Expression Builder — Build and explain cron schedules visually with a human-readable summary.
• Unix Timestamp / Epoch Converter — Convert between Unix timestamps and human-readable dates in any timezone.
• Base64 Encoder / Decoder — Encode and decode Base64 strings, including URL-safe Base64.
• Regex Tester — Test regular expressions with live match highlighting, group capture and flag support.
• Diff Checker — Compare two text blocks and highlight additions, deletions and changes line by line.
• UUID Generator — Generate v4 UUIDs in bulk. Copy one or all with a single click.
• Hash Generator — Compute MD5, SHA-1, SHA-256 and SHA-512 hashes of any text string.
• URL Encoder / Decoder — Encode special characters for safe use in URLs or decode encoded strings.
• HTML Entity Encoder — Convert characters like < > & to their HTML entity equivalents.
• Number Base Converter — Convert between decimal, binary, octal and hexadecimal.
• CSS Minifier / Formatter — Minify CSS for production or expand for readability.

How to Use DevLab

1. Open DevLab at nxtcraft.github.io/devlab — no login needed.
2. Select the tool from the left sidebar or tab bar.
3. Paste or type your input (JSON, JWT, regex pattern, SQL query, etc.) into the input panel.
4. The formatted or decoded output appears instantly in the right panel.
5. Click Copy to copy the result to clipboard.

JSON Formatter — Common Use Cases

Paste a minified JSON response from an API and DevLab formats it with proper indentation and colour coding. If your JSON has a syntax error — a missing comma, unclosed bracket or unquoted key — it shows the exact line and character where the error occurs, making debugging fast.

The JSON ↔ CSV tool is useful when you receive API data as a JSON array and need to open it in Excel or Google Sheets. It flattens the first level of keys into CSV columns.

JWT Decoder

A JWT (JSON Web Token) has three parts separated by dots: header.payload.signature. Each part is Base64URL-encoded. DevLab decodes the header (algorithm used) and payload (claims like user ID, expiry, roles) into readable JSON. It also shows the token's expiry time in a human-readable format. Note: DevLab does not verify the signature — use this for inspection only, not for security decisions.

Frequently Asked Questions