It depends on the implementation, e.g. Node has crypto.getRandomBytes()¹. If you mean the standard browser implementation, Crypto.getRandomValues()² may be wha

It depends on the implementation, e.g. Node has crypto.getRandomBytes()¹. If you mean the standard browser implementation, Crypto.getRandomValues()² may be what you're looking for. Note that the browser implementation of this is only a recommendation, so YMMV: > To guarantee enough performance, implementations are not using a truly random number generator, but they are using a pseudo-random number generator seeded with a value with enough entropy. The pseudo-random number generator algorithm (PRNG) may vary across user agents, but is suitable for cryptographic purposes. Implementations are required to use a seed with enough entropy, like a system-level entropy source. > [...] > There is no minimum degree of entropy mandated by the Web Cryptography specification. User agents are instead urged to provide the best entropy they can when generating random numbers, using a well-defined, efficient pseudorandom number generator built into the user agent itself, but seeded with values taken from an external source of pseudorandom numbers, such as a platform-specific random number function, the Unix /dev/urandom device, or other source of random or pseudorandom data. ¹ https://nodejs.org/api/crypto.html#crypto_crypto_randombytes_size_callback https://nodejs.org/api/crypto.html#crypto_crypto_randombytes... ² https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getR...