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Use SISMEMBER to check whether a value is a member of a set. The reply is 1 when it is and 0 when it is not or the key does not exist. The check is a constant-time lookup and transfers nothing but the answer, which is why sets are the right structure for membership questions such as permission or blocklist checks. Use SMISMEMBER to test several values in one call.

Syntax

Arguments

Response

The reply reports the result of the operation. Error replies have the same shape in RESP2 and RESP3 and are surfaced as exceptions by the SDKs below.
Client libraries often decode bulk strings, maps, sets, and numeric strings into language-native values. The table describes the Redis wire reply.

Examples

TCP examples use the TLS REDIS_URL from the Upstash console. REST examples use UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN.