# BIP39 Mnemonic Guide

Generate a BIP39 mnemonic phrase and derive its seed.

- Tool: https://ilham.dev/tools/bip39/
- Guide URL: https://ilham.dev/guides/bip39/
- Tool guides index: https://ilham.dev/guides/tools/
- Broader guide: Security and Cryptography Basics for Developers (https://ilham.dev/guides/security-cryptography-basics/)

## What it does

Generate a BIP-39 mnemonic phrase from a chosen word count and derive the seed from it, which is how a cryptocurrency wallet backs up a key as words. It also checks a phrase you were given for a valid checksum.

## Use the tool

Open https://ilham.dev/tools/bip39/, add the input the tool asks for, run it, and check the output before using it elsewhere.

## Input and output

- Input: text.
- Output: text.
- Category: Crypto.

## Privacy and processing
Processing happens locally in your browser. This tool does not upload the input to ilham.dev.

## Questions

### Is it safe to generate a wallet seed in a browser?

The entropy comes from crypto.getRandomValues, so the randomness is real. The risk is the page and the machine, not the maths. For anything holding real value, generate offline on a machine you control.

### Why does it reject my phrase?

The last word carries a checksum. If one word was mistyped the checksum fails and the phrase is rejected, which is the feature working as intended.