How to fix WRONGTYPE Operation against a key holding the wrong kind of value in Redis

Connect to Redis CLI and inspect what data type is actually stored at the problematic key:

redis-cli
> TYPE mykey
string

This tells you the current data type. Common outputs: string, list, set, zset (sorted set), hash, stream, none (key doesn't exist).

Match this type with the commands you are trying to run. For example, if TYPE returns "string" but you are running HGETALL, that's your mismatch.

If the key contains stale data and you want to use it as a different type, delete it first:

redis-cli
> DEL mykey
(integer) 1

After deletion, the key no longer exists and your next operation will create it fresh with the new type. Use DEL with caution in production to avoid data loss.

Ensure your code uses commands that match the actual data type at each key:

// If mykey stores a string
redis.get('mykey');  // Correct
redis.hgetall('mykey');  // Wrong - will cause WRONGTYPE

// If mykey stores a hash
redis.hgetall('mykey');  // Correct
redis.lpush('mykey', 'value');  // Wrong - will cause WRONGTYPE

// If mykey stores a list
redis.lpush('mykey', 'value');  // Correct
redis.sadd('mykey', 'member');  // Wrong - will cause WRONGTYPE

Be consistent about which data type each key holds throughout your application.

Instead of deleting the key, you can rename it to preserve the old data and free up the name for reuse:

redis-cli
> RENAME mykey mykey_old
OK

This allows you to migrate from one key to another without immediately losing data. You can later decide what to do with mykey_old (archive or delete).

To avoid future conflicts, adopt a naming convention that makes the data type explicit:

// Instead of: user:1
// Use:
redis.set('user:1:profile', jsonString);  // string type
redis.hset('user:1:hash', 'name', 'Alice');  // hash type
redis.lpush('user:1:logs', logEntry);  // list type

Prefixing or suffixing keys with their type makes it clear what operations are valid.

After deleting or renaming the problematic key, test your command again:

redis-cli
> HSET mykey field1 value1
(integer) 1

> HGETALL mykey
1) "field1"
2) "value1"

No WRONGTYPE error should appear if the key type now matches the command.