Best tools
Best Free Developer Utilities
Last updated · Reviewed by Daniel Agrici
The best free developer utilities are small, focused tools — UUID generators, Base64 encoders, hash generators, JWT decoders, and more — that run locally in the browser so you never paste sensitive values into a server.
These are the everyday utilities you reach for between bigger tasks: generate an ID, encode a string, decode a token, or test a pattern. Each one runs entirely in your browser, which matters when you're handling tokens or secrets.
The tools
UUID Generator
Generate cryptographically secure UUIDs (v4) in bulk.
Base64 Encoder/Decoder
Encode and decode Base64 strings and files instantly.
Hash Generator
Generate SHA-1, SHA-256, SHA-512, and MD5 hashes from text.
JWT Decoder
Decode and inspect JWT tokens — header, payload, and expiry.
URL Encoder / Decoder
Encode and decode URL components and query strings.
Password Generator
Generate secure random passwords with custom rules.
Timestamp Converter
Convert Unix timestamps to readable dates and vice versa.
Regex Tester
Test and debug regular expressions with live match highlighting.
Quick comparison
| Tool | What it does | Open |
|---|---|---|
| UUID Generator | UUID v4 uses 122 bits of cryptographic randomness — the probability of a collision when generating 1 billion IDs is less than 0.00000001%. Generated using crypto.randomUUID() directly in your browser. | Open → |
| Base64 Encoder/Decoder | Base64 encoding converts binary data to ASCII text using 64 printable characters, adding ~33% size overhead. It is commonly used in data URIs, JWT tokens, HTTP Basic Auth headers, and email attachments. | Open → |
| Hash Generator | SHA-256 is the recommended algorithm for most hashing needs — it produces a 256-bit (64 hex character) digest and has no known practical attacks. MD5 and SHA-1 are deprecated for security use but remain common for checksums. | Open → |
| JWT Decoder | A JWT (JSON Web Token) has three Base64url-encoded parts separated by dots: header (algorithm), payload (claims), and signature. Decoding shows the algorithm used and all payload claims like sub, iat, exp, and any custom data — no secret key required to read them. | Open → |
| URL Encoder / Decoder | URL encoding (percent encoding) replaces characters that are not allowed in URLs with a % followed by two hex digits. For example, a space becomes %20 and & becomes %26. You need this when passing special characters in query parameters to avoid breaking the URL structure. | Open → |
| Password Generator | A strong password should be at least 16 characters long and include uppercase, lowercase, numbers, and symbols. This generator uses crypto.getRandomValues() — the same cryptographic source used by operating systems for key generation. | Open → |
| Timestamp Converter | A Unix timestamp is the number of seconds (or milliseconds) elapsed since January 1, 1970 00:00:00 UTC. This tool converts any timestamp to a human-readable local date, UTC date, and relative time like '3 hours ago'. | Open → |
| Regex Tester | A regular expression (regex) is a pattern used to match, search, or replace text. This tester highlights all matches in real-time and shows each capture group, making it easy to iterate on patterns before using them in production code. | Open → |
Best for
Unique identifiers
UUID GeneratorGenerates RFC-compliant UUIDs in bulk for seeds, keys, and test data.
Inspecting tokens
JWT DecoderDecodes JWT header and payload locally so claims never leave your machine.
Encoding data
Base64 Encoder/DecoderEncodes and decodes Base64 for data URIs, headers, and config values.
Frequently asked questions
Is it safe to decode a JWT in an online tool?
Only if it runs in your browser. This JWT decoder parses the token locally with JavaScript and never sends it anywhere, so claims and signatures stay on your device. Avoid server-based decoders for real tokens.
What is a UUID and when should I use one?
A UUID is a 128-bit identifier that's practically guaranteed to be unique without a central authority, which makes it ideal for database keys, distributed systems, and test fixtures where you need IDs that won't collide.
Should I generate passwords in the browser?
A browser-based password generator using the cryptographically secure Web Crypto API is safe because the password is created locally and never transmitted. Always store the result in a password manager rather than reusing it.