Random String Generator

Random String Generator takes every character from crypto.getRandomValues, the browser's route to the operating system's cryptographic random source, and picks it by rejection sampling: a 32-bit sample landing in the leftover tail above the last whole multiple of the alphabet size is thrown away and redrawn rather than folded in with a remainder. That is what keeps a 62-character alphabet evenly represented instead of tilting towards its first few letters. There is no fallback here — a browser that cannot offer crypto.getRandomValues gets an error rather than a lesser generator quietly standing in for it.

Eight character sets are on offer: alphanumeric, hex, base64url, lowercase with digits, letters only, digits only for a PIN, the one labelled printable ASCII, and a custom set you type yourself. Read that ASCII label loosely — the set holds 90 characters, not the 95 that are actually printable, because the space, the two quote marks, the backtick and the backslash are all left out as characters that need escaping somewhere sooner or later. Duplicates in a custom set are removed before anything is drawn, so ABCA counts as three characters and the reported entropy reflects three. The Output setting sits above all of that. Choose one of the three raw-byte modes and both the character set and whatever is in the template box are ignored outright, Length becomes a count of random bytes, and each byte is rendered as hex, base64 or base64url — so 32 there returns 32 bytes, which is 64 hex characters or 43 base64url ones, not a 32-character string.

The input box is optional, and it holds templates rather than data. Each line is a shape: {32} becomes thirty-two random characters, so sk_live_{32} produces a token with a readable prefix, and {8}-{4}-{4}-{12} produces a grouped identifier. Lines beginning with # are ignored, a single placeholder is capped at 1,024 characters, and templates are cycled — three templates with a count of ten give lines four to ten those same three shapes again, in order. A line containing no {n} anywhere has the Length setting's worth of random characters appended to the end, which is worth knowing before you paste in a line of literal text. Where the templates draw different amounts, the summary reports the range instead of pretending one figure covers every line.

The entropy figure counts only the random characters, and that is the honest way to read it. A prefix, and every literal character in a template, adds nothing to the work of guessing a value: sk_live_ is a label, not a secret, and eight digits carry 26.6 bits whatever they are wrapped in. Two further limits matter. Nothing is recorded — no list of issued values is kept, no batch is checked for duplicates, and there is no way to revoke anything, so uniqueness rests on the size of the random space and on your own records. The ceilings are worth knowing too: 500 lines to a run, a Length of at most 256, and 1,024 characters from any one {n} — a template adds its placeholders up, so a line can finish well past what Length alone would ever give you. All of it happens in this browser tab; nothing is uploaded, and the results exist only here until you copy them.

Runs on your device. Your file is processed directly in this browser.