Everything in this group produces something new rather than transforming what you paste: an identifier, a secret, a number, a test fixture, or a symbol a scanner can read. Two questions decide which tool to use — does the output need to be unpredictable, and does it need to sort? Where unpredictability matters, the tools draw from the browser's cryptographic generator, crypto.getRandomValues, and never from Math.random, which was not designed to resist guessing.
For identifiers, the UUID generator makes version 4 and version 7 UUIDs in bulk. Version 4 is fully random and the safe default. Version 7 starts with a millisecond timestamp, so new rows land at the end of a database index instead of at random positions, which keeps primary-key indexes compact — at the cost of revealing when each record was created. The ULID generator offers the same ordering in a shorter, case-insensitive 26-character string and decodes the timestamp from an existing ULID, which helps when an ID is all a log line gives you.
The password generator builds random passwords and passphrases and reports their entropy from the size of the space it actually drew from, not from a rule of thumb about symbols. The random number generator picks integers in a range without modulo bias, the small skew that random() % n introduces whenever the range does not divide evenly. The fake data generator produces mock rows as JSON, CSV or SQL from a seed, so a fixture can be regenerated exactly — and because a seed reproduces everything, its output must never stand in for a real secret.
The last three produce symbols for scanners. The QR code generator encodes links, text and Wi-Fi credentials; a higher error-correction level lets a code survive a logo or a scuff at the cost of a denser grid. The Code 128 barcode generator encodes any ASCII text and switches code sets to keep the symbol short, which matters on a narrow label. The EAN-13 barcode generator calculates the check digit for retail product numbers, but the number itself has to come from GS1: drawing a barcode does not register a product, and retailers check.