How to fix ERR wrong number of arguments in Redis

Look at your error message—it should specify the command name. For example, 'ERR wrong number of arguments for set command' tells you it's the SET command.

Use redis-cli to look up the correct syntax. You can use:

help <commandname>

For example, help set will show the exact format and required vs optional arguments.

Or use the COMMAND INFO subcommand:

COMMAND INFO set

Remember that in Redis command syntax:
- GET requires exactly 1 argument: GET key
- MGET accepts multiple arguments: MGET key1 [key2] [key3]...
- SET requires at least 2 arguments: SET key value [EX|PX|EXAT|PXAT] [NX|XX]

Note: Command arity counts include the command name itself in the specification.

Adjust your command to match the documented format. Common fixes:

Missing value in SET:

// Wrong
SET mykey

// Correct
SET mykey myvalue

Extra arguments in GET:

// Wrong
GET mykey extra_arg

// Correct
GET mykey

Wrong HSET format (if using older Redis):

// Redis 3.0.0+ (multiple field-value pairs)
HSET myhash field1 value1 field2 value2

// Redis < 3.0.0 (one field-value pair only)
HSET myhash field1 value1

If you're using a Redis client library (node-redis, redis-py, Predis, etc.), ensure it's up-to-date. Older versions may have different argument handling:

# Node.js
npm list redis

# Python
pip show redis

Upgrade if you're on a very old version, as newer versions handle commands more correctly.

If you're using a client library, test your exact command syntax in redis-cli first to isolate the issue:

redis-cli
127.0.0.1:6379> SET mykey myvalue
OK
127.0.0.1:6379> GET mykey
"myvalue"

Once it works in redis-cli, the syntax is correct and the issue is likely in how you're passing arguments from your code.