Best Free Developer Tools & Utilities Online (2025)
Format JSON, test regex, encode Base64, generate UUIDs and QR codes, and decode JWTs with free browser-based developer utilities.
Guide Overview
Every developer has a collection of bookmarked utilities for the small tasks that interrupt focus during coding. These browser-based tools handle formatting, encoding, testing, and generating so you can get back to the real work in seconds. No installation, no dependencies, no leaving the browser.
Focus: developer utilities, encoding, formatting, testing
JSON Formatting and Validation
Dealing with minified JSON from an API response or a collapsed config file is a constant developer annoyance. The JSON formatter prettifies, validates, and highlights syntax errors in real time as you paste or type. It handles deeply nested structures, arrays, and large payloads without freezing your browser tab. When you spot an error, the tool points to the exact line and character position, saving minutes of manual debugging.
Regular Expression Testing Without the Headache
Writing regex patterns is part art, part science, and mostly trial and error. The regex tester lets you write a pattern, paste test strings, and see matches highlighted in real time. It supports JavaScript regex syntax with flags for case-insensitive, multiline, and global matching. You can also see capture groups extracted and labeled, which is invaluable when building parsers or input validators. The visual feedback loop makes pattern development significantly faster than testing in code.
Encoding, Decoding, and Converting
Base64 encoding, URL encoding, and JWT decoding are tasks developers perform daily but rarely have memorized. The Base64 converter encodes and decodes strings and files instantly. The URL encoder handles special characters for query parameters and path segments. The JWT decoder splits a token into its header, payload, and signature sections with claim timestamps converted to readable dates. None of these tools transmit your data anywhere, which matters when working with authentication tokens.
Generating UUIDs, QR Codes, and Colors
The UUID generator creates v4 universally unique identifiers that you can copy with a single click, which is useful for database seeding, API testing, and configuration. The QR code generator converts any URL or text into a scannable code that you can download as an image. The color converter translates between HEX, RGB, HSL, and CMYK formats with a visual preview, essential when working on UI designs or theming systems.
Timestamps and Cron Expressions Demystified
Unix timestamps are efficient for databases but unreadable by humans. The timestamp converter translates between Unix epoch seconds and human-readable dates in any timezone, handling both directions instantly. The cron expression parser takes a scheduling expression and shows in plain English when it will fire, along with the next several execution times. This is invaluable when setting up scheduled tasks or debugging cron jobs that are not running when expected.
Tools in This Guide
Use these tools in sequence based on your workflow needs.
Color Converter
Convert colors between HEX, RGB, HSL, and CMYK formats. Includes a color picker and palette generator.
Use tool →Base64 Encoder / Decoder
Encode text to Base64 or decode Base64 strings instantly. Supports UTF-8 and file encoding.
Use tool →QR Code Generator
Generate QR codes for URLs, text, Wi-Fi, email, and more. Download as PNG or SVG.
Use tool →JSON Formatter
Format, validate, and minify JSON with syntax highlighting and instant error detection.
Use tool →Regex Tester
Test regular expressions in real time with match highlighting, flags, and capture group inspection.
Use tool →URL Encoder/Decoder
Encode and decode URL strings for safe query parameters, path segments, and web debugging.
Use tool →Unix Timestamp Converter
Convert Unix timestamps to human-readable date/time and convert dates back to epoch format.
Use tool →JWT Decoder
Decode JWT headers and payloads, inspect claims, and quickly check token expiry timestamps.
Use tool →UUID Generator
Generate secure UUID v4 values in bulk with formatting options for braces, hyphens, and uppercase output.
Use tool →Cron Expression Parser
Validate cron syntax and preview upcoming run times in UTC to debug schedules before deployment.
Use tool →Frequently Asked Questions
Is the JSON formatter safe for sensitive data?
Which regex flavor does the tester use?
Can I decode an expired JWT?
What UUID version does the generator create?
How do I read a cron expression?
Can I generate QR codes for Wi-Fi networks?
Last updated: June 1, 2025