Free Developer Tools Online — Complete Toolkit (2026)
TL;DR
UtilDaily bundles 40 free developer utilities — JSON formatter, Base64 encoder, UUID generator, regex tester, hash generator, JWT decoder, cron builder, and more — into one page that works fully in your browser. Nothing leaves your device, so it is safe to paste API tokens, JWTs, and private payloads. No sign-up, no install, no usage limits.
How do I format and validate code or data?
Reading a minified API response or a one-line JSON dump is painful — pretty-printing it makes structure, types, and missing fields obvious. Use the JSON formatter for object payloads, the markdown previewer for documentation drafts, the regex tester for pattern debugging, and the JS minifier when you need to ship the opposite direction.
JSON Formatter & Validator
Format, validate, and minify JSON data instantly.
Markdown Preview
Live Markdown editor with split-pane preview, GFM support, and HTML export.
Regex Tester
Test regular expressions in real-time with match highlighting and capture group display.
JavaScript Minifier
Minify JavaScript by removing whitespace, comments, and unnecessary characters. Shows original vs. minified size and reduction percentage.
How do I encode, decode, and hash data?
Working with HTTP, JWTs, signed URLs, and embedded images means encoding constantly: Base64 to embed binary in JSON, URL-encoding for query strings, JWT decoding to inspect claims, and hashing to checksum or fingerprint content. Every encoder runs locally so you can paste sensitive payloads safely.
Base64 Encoder & Decoder
Encode text to Base64, or decode Base64 back to plain text. Supports full UTF-8.
URL Encoder & Decoder
Encode or decode URL components and query strings.
JWT Decoder
Decode and inspect JSON Web Tokens — view header, payload, and expiry status instantly.
Hash Generator
Generate MD5, SHA-1, and SHA-256 hashes from any text using your browser's built-in crypto.
How do I generate UUIDs, random tokens, and test data?
From RFC 4122 v4 UUIDs for primary keys, to cryptographically random strings for API tokens, to placeholder text for layout work — use the right generator for the job. Every generator uses Crypto.getRandomValues() for entropy, not Math.random().
UUID v4 Generator
Generate random UUIDs (v4) in bulk with one click.
Random String Generator
Generate random strings with custom length and character sets.
Password Generator
Generate secure passwords with crypto.getRandomValues(). Length slider, character sets, entropy strength meter.
Lorem Ipsum Generator
Generate lorem ipsum placeholder text by paragraphs, sentences, or words.
How do I convert between data formats?
JSON ↔ CSV for spreadsheet imports, hex ↔ RGB for design handoffs, decimal ↔ binary or hexadecimal for low-level work, and Unix epoch ↔ ISO 8601 for log debugging. Every converter is bidirectional — paste either side and the other updates instantly.
JSON to CSV Converter
Convert JSON arrays to CSV format with one click. Supports nested objects.
CSV to JSON Converter
Convert CSV files or pasted data to JSON arrays. Auto-detects headers and types.
Hex to RGB Color Converter
Convert hex color codes to RGB and HSL values instantly. Includes color picker, CSS variable output, and example colors.
Number Base Converter
Convert numbers between binary, decimal, octal, and hexadecimal. Includes two's complement representation and ASCII character mapping for developer reference.
Unix Timestamp Converter
Convert Unix timestamps to human-readable dates and back. Auto-detects seconds vs milliseconds.
Plain Text Converter
Convert HTML to plain text, strip Markdown syntax, or extract text from RTF with 3 conversion modes.
How do I generate cron expressions and favicons?
Two niche-but-frequent dev needs: building a cron expression for a scheduled job (and reading one someone else wrote), and generating a multi-size favicon for a new site. Both are 30-second tasks with the right tool, 30-minute tasks without one.
Pick the right encoder / converter for the job
Encoding choices come up constantly and the differences matter. This table maps the question you have to the format and tool.
| Use case | Format | Tool |
|---|---|---|
| Embed binary in JSON / data URI | Base64 (RFC 4648) | Base64 Encoder & Decoder |
| Safely include data in URL query strings | Percent / URL encoding (RFC 3986) | URL Encoder & Decoder |
| Inspect a JWT's header & claims (decode only) | JWT (base64url-encoded) | JWT Decoder |
| Generate a database primary key | UUID v4 (RFC 4122) | UUID v4 Generator |
| Generate an API token / session ID | Cryptographically random string | Random String Generator |
| Generate a strong password | Random with character classes | Password Generator |
| Hash a file or string for checksum | SHA-256 / SHA-512 | Hash Generator |
| Convert API CSV export to JSON | JSON | CSV to JSON Converter |
| Convert JSON to spreadsheet-friendly | CSV | JSON to CSV Converter |
| Convert decimal to binary / hex | Number bases | Number Base Converter |
| Convert hex colour to RGB / HSL | CSS colour formats | Hex to RGB Color Converter |
| Read or write a Unix timestamp | Unix epoch ↔ ISO 8601 | Unix Timestamp Converter |
| Strip HTML tags from rich content | HTML → plain text | Plain Text Converter |
| Test a regex against sample text | Regex (PCRE-compatible) | Regex Tester |
| Build a cron expression | 5- or 6-field cron | Cron Expression Generator |
| Generate a favicon for a new site | ICO / PNG sizes | Favicon Generator |
All developer tools (40)
Every developer tool on UtilDaily, alphabetised. Each one runs in your browser, uses only Web APIs, and ships zero data to a server.
JSON Formatter & Validator
Format, validate, and minify JSON data instantly.
Base64 Encoder & Decoder
Encode text to Base64, or decode Base64 back to plain text. Supports full UTF-8.
UUID v4 Generator
Generate random UUIDs (v4) in bulk with one click.
URL Encoder & Decoder
Encode or decode URL components and query strings.
JSON to CSV Converter
Convert JSON arrays to CSV format with one click. Supports nested objects.
Random Wheel Spinner
Spin the wheel to pick random winners from your list. Three modes, CSV import, history tracking.
CSV to JSON Converter
Convert CSV files or pasted data to JSON arrays. Auto-detects headers and types.
Random Number & Dice
Generate random numbers, flip a coin, or roll dice — all in one place.
Random List Picker
Paste a list of items and pick random winners instantly. Also works as a list randomizer and shuffler.
Hash Generator
Generate MD5, SHA-1, and SHA-256 hashes from any text using your browser's built-in crypto.
Nickname Generator
Generate random nicknames, gamer tags, and fantasy names instantly.
Favicon Generator
Create favicons from images, text, or emoji. Generate multiple sizes with live preview.
Case Converter
Convert text between 7 case styles: sentence, lower, UPPER, Title, Capitalized, aLtErNaTiNg, InVeRsE.
Text Cleaner
Remove duplicate lines, extra whitespace, line breaks, and unwanted characters with 7 cleaning modes.
Text Transformer
Reverse text, repeat N times, sort lines alphabetically, and find/replace with 4 transformation modes.
Plain Text Converter
Convert HTML to plain text, strip Markdown syntax, or extract text from RTF with 3 conversion modes.
Word Cloud Generator
Generate beautiful word clouds from text with customizable colors, sizes, and layouts.
Roman Numeral Converter
Convert between numbers and Roman numerals (I, V, X, L, C, D, M) with validation and date formatting.
QR Code Generator
Generate QR codes from URLs, text, or email. Download as PNG.
Password Generator
Generate secure passwords with crypto.getRandomValues(). Length slider, character sets, entropy strength meter.
Temperature Converter
Convert temperatures between Celsius, Fahrenheit, Kelvin, and Rankine in real time.
Lorem Ipsum Generator
Generate lorem ipsum placeholder text by paragraphs, sentences, or words.
JWT Decoder
Decode and inspect JSON Web Tokens — view header, payload, and expiry status instantly.
Password Strength Checker
Check how strong your password is with realistic crack-time estimates and improvement suggestions.
Morse Code Converter
Translate text to Morse code and decode Morse to English instantly.
KM to Miles Converter
Convert kilometers to miles and miles to km with a simple calculator.
MM to Inches Converter
Convert millimeters to inches and inches to mm with precision.
Random String Generator
Generate random strings with custom length and character sets.
Barcode Generator
Generate Code 128 barcodes from any text and download as SVG. No sign-up required.
Random Number Generator
Generate cryptographically random numbers in any range — dice, lottery, statistics, or any custom min/max.
Random Word Generator
Generate random English words filtered by type (noun/verb/adjective/adverb), length, and starting letter.
Username Generator
Generate creative usernames for gaming, social media, or professional profiles in 5 styles.
Number to Words Converter
Convert numbers to English words in cardinal, ordinal, or check-writing format up to quadrillions.
KG to LBS Converter
Convert kilograms to pounds and back instantly. See results in lbs, oz, and stones with a quick-reference table.
JavaScript Minifier
Minify JavaScript by removing whitespace, comments, and unnecessary characters. Shows original vs. minified size and reduction percentage.
Cooking Converter
Convert between cooking measurements: oz to ml, cups to grams, teaspoons, tablespoons, pints, and liters. Includes ingredient density selector for accurate cup-to-gram conversion.
Speed Converter
Convert between speed units: knots, mph, km/h, meters per second, and feet per second. Includes Beaufort wind scale reference and common speed benchmarks.
Area Converter
Convert between area units: square feet, square meters, acres, hectares, square yards, square miles, and square kilometers. Includes real estate size reference table.
Liquid Volume Converter
Convert between liquid volume units: US/UK gallons, liters, fluid ounces, cups, pints, and quarts. Clearly distinguishes between US and Imperial measurements.
Number Base Converter
Convert numbers between binary, decimal, octal, and hexadecimal. Includes two's complement representation and ASCII character mapping for developer reference.
Frequently asked questions
Are these developer tools really free?
Yes. Every developer tool on UtilDaily is completely free with no usage limits, no sign-up, and no paid tiers. The site is supported by non-intrusive advertising.
Is it safe to paste API keys, JWTs or tokens into these tools?
Yes — every tool runs in your browser via JavaScript. Tokens, payloads, and configuration data never leave your device. You can verify this by opening DevTools' Network tab while using any tool: no outbound requests carry your data.
Do these tools work offline?
Most developer tools work offline after your first visit. JSON formatting, Base64 encoding, UUID generation, hashing, regex testing, and most converters require no external resources and continue working without a network connection.
What is the difference between encoding and encryption?
Encoding (Base64, URL-encoding, hex) is a public, reversible transformation that makes data safe to transmit — anyone can decode it. Encryption (AES, RSA) requires a key and prevents anyone without the key from reading the data. Base64 is encoding, not encryption — never use it to 'protect' secrets.
Which UUID version should I use?
UUID v4 (random) is the right default for almost every application — database primary keys, API request IDs, distributed system identifiers. Use v5 (name-based, SHA-1) when you need a deterministic ID derived from input. v1 (timestamp + MAC) leaks information and is rarely the right choice today. RFC 4122 defines all versions.
How do I format minified JSON?
Paste the minified JSON into our JSON formatter and click Format — it pretty-prints with 2- or 4-space indentation, validates the syntax, and highlights any errors with line numbers. The reverse (minify pretty-printed JSON) is one click away on the same tool.
Are these hashes cryptographically secure?
MD5 and SHA-1 are not — they are kept for legacy compatibility (file checksums, Git internals) but should never be used for password hashing or signatures. SHA-256 and SHA-512 are still cryptographically secure for general-purpose hashing. For password storage, use a dedicated KDF (Argon2, bcrypt, scrypt) — not a raw hash.
Why use a regex tester before deploying a regex?
Regular expressions can match unexpected inputs and silently fail on edge cases. The regex tester lets you paste real sample data, see exactly which substrings match, inspect capture groups, and verify behaviour with the same flags you will use in production — all without firing up a sandbox.
Which browsers are supported?
All evergreen browsers — Chrome, Firefox, Safari, and Edge. The tools use standard Web APIs including the Web Crypto API for hashing and encoding operations, available in every modern browser.
References
- 1.RFC 4648 — The Base16, Base32, and Base64 Data Encodings — IETF
- 2.RFC 4122 — A Universally Unique IDentifier (UUID) URN Namespace — IETF
- 3.RFC 3339 — Date and Time on the Internet: Timestamps — IETF
- 4.Web Crypto API — MDN Web Docs (Mozilla)
- 5.Regular expressions — MDN Web Docs (Mozilla)