Validate Seed Phrase Checksum

WHAT IT DOES

This tool validates the checksum of a BIP39 seed phrase, instantly determining whether a 12-word or 24-word mnemonic is cryptographically valid. The tool counts the words, verifies that each word exists in the BIP39 wordlist, and computes the embedded checksum to ensure the phrase was correctly generated. A valid checksum confirms that the phrase has not been mistyped and is structurally correct, while an invalid checksum indicates a transcription error, a missing word, or a phrase that was not properly generated.

The tool accepts both 12-word (128-bit entropy) and 24-word (256-bit entropy) BIP39 phrases, which are the two most common standards used by hardware wallets and software wallets. Validation is performed entirely in your browser using the ethers.js library. No data is ever transmitted to any server or stored anywhere — the phrase is processed locally and remains only in memory during the validation.

HOW TO USE

Enter your 12-word or 24-word seed phrase into the text area, separated by spaces or line breaks. The tool will automatically count the words and display the count. Click the "validate" button or simply wait for the auto-validation to trigger. The tool will instantly check the phrase and display one of three results: "valid checksum" (green) indicating the phrase is cryptographically correct, "invalid checksum" (red) indicating a problem with the phrase, or "invalid word count" (red) if the phrase does not contain 12 or 24 words.

For valid phrases, the tool also displays the entropy hex and checksum hex for advanced verification. The word count is clearly shown, and any invalid words are flagged. This helps you quickly identify whether a seed phrase you have written down was transcribed correctly before attempting to import it into a wallet.

TECHNICAL MECHANISM — BIP39 CHECKSUM VERIFICATION

The tool uses the ethers.js isValidMnemonic() function, which implements the complete BIP39 validation algorithm. This algorithm takes the mnemonic phrase, splits it into words, and checks each word against the BIP39 wordlist of 2048 words. It then reconstructs the original entropy by converting each word back to its 11-bit index, concatenating these bits, and extracting the entropy bits followed by the checksum bits.

The checksum is computed by taking the SHA-256 hash of the entropy bytes, and the first N bits of this hash (4 bits for 12-word phrases, 8 bits for 24-word phrases) must exactly match the checksum bits embedded in the mnemonic. If all words are in the wordlist and the checksum matches, the phrase is considered valid. The tool also uses mnemonicToEntropy() to extract the entropy and display it alongside the checksum for users who want to verify the validation process independently.

WHAT IT CANNOT SEE

This tool cannot verify whether the seed phrase corresponds to a real wallet address on any blockchain — it only validates the structural integrity and checksum of the phrase. It cannot display balances, transaction history, or any on-chain data associated with the wallet the phrase would generate. It cannot interact with non-EVM chains or validate phrases that use different wordlists or mnemonic standards. The tool cannot recover lost seed phrases, correct invalid ones, or suggest missing words. It also cannot ensure the security of the phrase if it has already been exposed or compromised. The tool does not check if the phrase is already associated with an existing wallet or if it has been used before.

PLEASE NOTE — EVM CHAINS ONLY

This tool validates BIP39 seed phrases that are compatible with Ethereum Virtual Machine (EVM) wallets and networks, including Ethereum, Polygon, Arbitrum, Optimism, Avalanche, BNB Smart Chain, and Base. However, a valid BIP39 phrase will generate a wallet address on any BIP39-compatible chain, including non-EVM chains. The tool does not validate phrases from other mnemonic standards such as SLIP-0039 or custom wordlists. It also does not verify derivation paths (BIP32, BIP44) — it only validates the BIP39 mnemonic itself. For full wallet verification, you must import the phrase into a compatible wallet application and check the derived address.