Developer Tools
Encode, decode, hash and test — with the browser's own engines, so results match your code exactly. Tokens, payloads and secrets are exactly what shouldn't touch third-party servers: here they never do.
- Base64 Encoder / Decoder Base64 turns any bytes into 64 safe characters
- URL Encoder / Decoder Spaces become %20, & becomes %26
- HTML Entities Encoder / Decoder Turn < into < so it displays instead of rendering
- SHA Hash Generator One input, four hashes
- JWT Decoder Paste a JWT and read its header and payload instantly
- Regex Tester Type a pattern, paste test text, see every match with its position and capture groups
- Number Base Converter 255 = 0xff = 0o377 = 0b11111111
- LLM Token Counter & Cost Calculator Paste a prompt, count its tokens, see the cost per model
- Ethereum Unit Converter (Wei, Gwei, Ether) Convert between Ethereum units
- Keccak-256 / SHA-3 Hash & Function Selector Hash text with Keccak-256 (the hash Ethereum actually uses) or NIST SHA3-256
- EIP-55 Ethereum Address Checksum Check whether an Ethereum address has a valid EIP-55 checksum, and convert any address to its correct mixed-case form
- Query String Parser Paste a URL or query string to see its parameters as clean JSON
- HTTP Status Code Lookup Enter one or more HTTP status codes to see their names, meanings and class (2xx success, 4xx client error, and so on).
- JSON String Escaper / Unescaper Turn raw text into a safe JSON string value
- Unicode Escape Converter Turn accented letters, emoji and other non-ASCII characters into \uXXXX escapes
- Text to Hex Converter Turn any text into its UTF-8 hex bytes
Developer utilities that keep secrets local
These are the small, sharp tools you reach for a dozen times a day: Base64 and URL encoding, JSON and other formatters, hashes (SHA family via the browser's Web Crypto), JWT decoding, regex testing, an exact LLM token counter, and Ethereum helpers (BigInt-exact wei⇄ether, Keccak-256, EIP-55 checksums). Each does one job cleanly and shows its working.
Crucially, they run entirely in your browser — so pasting an API key, a private JWT, a config file or a wallet address never sends it to a server. That's the difference between a convenient tool and a liability: your secrets stay on your machine, and the tools keep working offline.
Frequently asked questions
Why does client-side matter especially for developer tools?
Because the inputs are secrets: JWTs are live credentials, Base64 blobs are often API payloads, and hashed strings can be keys. Pasting those into a server-backed tool hands them to that server. Every tool here runs locally — verify with the network tab or by going offline.
Do these tools match what my code does?
Yes, by construction: the regex tester runs the browser's actual RegExp engine, hashing uses the native Web Crypto implementation, and Base64/URL encoding use the platform functions with correct UTF-8 handling.
Why is there no MD5?
The Web Crypto API excludes it deliberately — MD5 collisions are practical, so it fails as a security primitive. SHA-256 is the modern default for everything MD5 used to do.