How to fix NOPROTO sorry, this protocol version is not supported in Redis

Connect to the Redis server and verify its version and protocol capabilities:

# Check Redis version
redis-cli INFO server | grep redis_version

# Test if HELLO command is supported
redis-cli HELLO 3

# Expected output if RESP3 is supported:
# 1) "server"
# 2) "redis"
# 3) "version"
# 4) "7.2.0"
# ...

# If RESP3 is not supported, you'll see:
# (error) NOPROTO sorry, this protocol version is not supported
# OR
# (error) ERR unknown command 'HELLO'

If the version is below 6.0, RESP3 is not available. If it's 7.2+ but returns NOPROTO, RESP3 may be disabled in configuration.

Most modern Redis clients support protocol version configuration. Set it to RESP2 to avoid the handshake error:

Node.js (node-redis v4+):

import { createClient } from 'redis';

const client = createClient({
  url: 'redis://localhost:6379',
  // Force RESP2
  RESP: 2
});

await client.connect();

Go (go-redis v9+):

import "github.com/redis/go-redis/v9"

client := redis.NewClient(&redis.Options{
    Addr:     "localhost:6379",
    Protocol: 2, // Force RESP2
})

Java (Lettuce 6+):

RedisURI redisUri = RedisURI.Builder
    .redis("localhost", 6379)
    .build();

RedisClient client = RedisClient.create(redisUri);
// Lettuce should auto-fallback on NOPROTO, but you can disable RESP3:
client.setOptions(ClientOptions.builder()
    .protocolVersion(ProtocolVersion.RESP2)
    .build());

Check your client library documentation for the exact option name (protocol, RESP, protocolVersion).

If your Redis version is 7.2+ and RESP3 is disabled, you can enable it via configuration or during database creation:

For Redis Enterprise/Cloud (upgraded databases):
RESP3 may be disabled by default on databases upgraded from earlier versions. Check with your provider or create a new database instance that has RESP3 enabled by default.

For self-hosted Redis 7.2+:
There is no explicit redis.conf setting to disable RESP3—it should be available by default. If HELLO 3 still fails, verify:

# Ensure no custom module or proxy is blocking HELLO
redis-cli COMMAND INFO HELLO

# Check for any custom command rename/disable in redis.conf
grep -i "rename-command" /etc/redis/redis.conf

If using a Redis cluster or proxy like Twemproxy, upgrade to versions that support RESP3 or continue using RESP2 on the client.

Older client versions may not implement automatic fallback from RESP3 to RESP2. Upgrade to the latest stable version:

# Node.js
npm install redis@latest

# Python
pip install --upgrade redis

# Go
go get github.com/redis/go-redis/v9@latest

# Java (Maven)
# Update pom.xml to Lettuce 6.3+ which includes better NOPROTO handling

Lettuce versions 6.3+ and go-redis v9.3+ implement automatic protocol downgrade when receiving NOPROTO, so the connection retries with RESP2 without user intervention. Check the release notes for your client library to confirm this feature is included.