All Developer Tools

Browse all 50 free online tools. Every tool runs entirely in your browser with no sign-up required.

Hash Generators

Generate cryptographic hashes with SHA-256, MD5, Keccak256, and more. Batch hashing, event hashes, and function selectors.

Keccak256 Hash Generator

Generate Keccak256 hashes from text input. The hash function used by Ethereum and Solidity.

SHA-256 Hash Generator

Generate SHA-256 hashes from text or hex input using the Web Crypto API. Compare SHA-256 with Keccak256 for Ethereum development.

MD5 Hash Generator

Generate MD5 hashes from text input online. Pure JavaScript implementation with RFC 1321 test vectors. Note: MD5 is not cryptographically secure.

Batch Keccak256 Hasher

Hash multiple inputs at once with Keccak256. Get hashes and function selectors for multiple function signatures, storage keys, or arbitrary text.

Solidity Event Hash Calculator

Calculate keccak256 hashes for Solidity event signatures. Get topic 0 values for filtering Ethereum logs.

Function Selector Lookup

Calculate Solidity function selectors from signatures using keccak256. Browse a table of 30+ common ERC-20, ERC-721, and Ownable selectors.

EIP-712 Typed Data Hasher

Hash EIP-712 typed structured data online. Compute domain separator, struct hash, and final signing hash for permits and gasless transactions.

Merkle Proof Generator

Generate and verify Merkle proofs for whitelists and allowlists. Build Merkle trees with keccak256 hashing.

Text Tools

Count words and characters, convert text case, compare diffs, generate lorem ipsum, and preview markdown.

Word Counter

Count words, characters, sentences, and paragraphs instantly. Get reading time estimates, character counts, and word frequency analysis.

Character Counter

Count characters with and without spaces. Check text against Twitter, meta description, and other platform character limits in real time.

Text Case Converter

Convert text between camelCase, PascalCase, snake_case, kebab-case, UPPERCASE, lowercase, Title Case, CONSTANT_CASE, and more.

Diff Checker

Compare two texts and see the differences highlighted line by line. Online diff tool with added, removed, and unchanged line detection.

Lorem Ipsum Generator

Generate lorem ipsum placeholder text by paragraphs, sentences, or words. Free dummy text generator for design and development.

Markdown Preview

Write markdown and see a live rendered preview side by side. Supports headers, bold, italic, code blocks, lists, links, and more.

Converters

Convert between JSON, CSV, Base64, hex, color formats, number bases, and more.

JSON to CSV Converter

Convert JSON arrays to CSV and CSV to JSON online. Supports custom delimiters, proper escaping, nested objects, and file download.

JSON Formatter / Validator

Format, minify, and validate JSON data online. Pretty-print with configurable indentation and see detailed error positions for invalid JSON.

Base64 Encoder / Decoder

Encode and decode Base64 strings online. Supports text and hex input with URL-safe Base64 option for Ethereum development.

Hex / Decimal Converter

Convert between hexadecimal and decimal numbers. Useful for Ethereum block numbers, values, and calldata.

Color Picker / Converter

Pick colors and convert between HEX, RGB, and HSL formats. Check WCAG contrast ratios, generate shades, and get CSS values.

Number Base Converter

Convert numbers between binary, octal, decimal, and hexadecimal online. Supports arbitrarily large numbers with BigInt.

Image to Base64 Converter

Convert images to Base64 encoded strings online. Drag and drop PNG, JPG, GIF, SVG, or WebP files to get Data URIs for HTML, CSS, and JSON.

HTML Encoder / Decoder

Encode and decode HTML entities online. Convert special characters to HTML entities for safe display in web pages.

URL Encoder / Decoder

Encode and decode URL components online. Compare encodeURIComponent vs encodeURI with a common URL encodings reference table.

Encoding & Conversion

Encode and decode ABI data, RLP, UTF-8/hex, bytes32, and Unix timestamps for Ethereum development.

ABI Encoder / Decoder

Encode and decode Ethereum ABI data. Input function signatures and parameters to generate calldata.

UTF-8 / Hex / Bytes Converter

Convert between UTF-8 text, hexadecimal strings, and byte arrays. Essential for encoding and debugging Ethereum data.

RLP Encoder / Decoder

Encode and decode Recursive Length Prefix (RLP) data. The serialization format used by Ethereum transactions and blocks.

Unix Timestamp Converter

Convert between Unix timestamps and human-readable dates. Includes notable Ethereum timestamps and relative time display.

Bytes32 / String Converter

Convert between bytes32 hex, UTF-8 strings, numbers, and addresses. Visualize padding for Solidity bytes32 values.

Address & Keys

Validate addresses, convert checksums, generate mnemonics, derive keys, verify signatures, and calculate CREATE2 addresses.

Checksum Address Converter

Convert Ethereum addresses to EIP-55 checksummed format for safe usage in transactions.

Address Validator

Validate cryptocurrency wallet addresses for Ethereum, Bitcoin, and Solana.

Private Key to Address

Derive Ethereum public key and checksummed address from a private key. Shows uncompressed and compressed public keys.

BIP39 Mnemonic Generator

Generate secure BIP39 mnemonic seed phrases (12 or 24 words) for cryptocurrency wallets.

Signature Signer & Verifier

Sign messages with a private key and verify Ethereum EIP-191 signatures. Recover signer addresses from signed messages.

CREATE2 Address Calculator

Calculate deterministic smart contract addresses using CREATE2. Input deployer address, salt, and init code hash to predict deployment addresses.

Smart Contract Analysis

Decode calldata, analyze ERC-20 transfers, decode Solidity errors, calculate storage slots, and check contract sizes.

Calldata Decoder

Decode raw Ethereum calldata hex into human-readable function calls and parameters.

Storage Slot Calculator

Calculate Solidity storage slots for variables, mappings, and nested mappings using keccak256.

ERC-20 Token Info Decoder

Decode ERC-20 token function calls and event logs from raw transaction data.

Solidity Error Decoder

Decode Solidity revert data into human-readable error messages. Supports Error(string), Panic(uint256) codes, and custom errors.

Contract Size Calculator

Check if your Solidity contract bytecode fits within the 24KB EIP-170 limit. Paste bytecode to see size, percentage used, and optimization tips.

Gas & Units

Convert ETH units, calculate gas fees, convert token amounts, and look up beacon chain epochs and slots.

ETH Unit Converter

Convert between Ethereum units: Wei, Gwei, and ETH. Essential for gas and transaction calculations.

Gas Fee Calculator

Calculate Ethereum transaction costs from gas limit and gas price. Estimate fees in ETH and USD.

Token Unit Converter

Convert between human-readable token amounts and raw values for any ERC-20 token. Supports custom decimals for USDC, WBTC, ETH, and more.

Ethereum Epoch / Slot Calculator

Convert between Ethereum beacon chain epochs, slots, timestamps, and dates. Live current epoch and slot display with notable epoch references.

Developer Utilities

Decode JWTs, generate UUIDs, test regex patterns, parse cron expressions, generate slugs, QR codes, and passwords.