APPEND - Upstash Documentation

Use APPEND to add a value to the end of the string stored at a key.

If the key does not exist it is created with the given value, so the command behaves like SET on a fresh key. The reply is the length of the string after the append. Redis grows the underlying buffer with room to spare, so repeated appends stay cheap, which makes this a reasonable way to accumulate log lines or serialized events into one value; GETRANGE can then read back a slice without transferring the whole thing.

Syntax#

APPEND <key> <value>

Arguments#

Argument	Required	Repeatable	Description
`<key>`	Yes	No	Redis key targeted by the command.
`<value>`	Yes	No	String appended to the current value.

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.

Protocol	Reply
RESP2	Integer
RESP3	Integer

Note

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.

Redis CLI

APPEND my-key value

@upstash/redis

import { Redis } from "@upstash/redis";const redis = Redis.fromEnv();await redis.append(key, "Hello");// returns 5

upstash_redis

from upstash_redis import Redisredis = Redis.from_env()result = redis.append("my-key", "value")print(result)

ioredis

import Redis from "ioredis";const redis = new Redis(process.env.REDIS_URL!);const result = await redis.append("my-key", "value");console.log(result);

node-redis

import { createClient } from "redis";const client = await createClient({ url: process.env.REDIS_URL })  .on("error", console.error)  .connect();const result = await client.append("my-key", "value");console.log(result);

redis-py

import osimport redisclient = redis.from_url(os.environ["REDIS_URL"])result = client.append("my-key", "value")print(result)

go-redis

package mainimport (    "context"    "fmt"    "os"    "github.com/redis/go-redis/v9")func main() {    opts, err := redis.ParseURL(os.Getenv("REDIS_URL"))    if err != nil {        panic(err)    }    client := redis.NewClient(opts)    result, err := client.Append(context.Background(), "my-key", "value").Result()    if err != nil {        panic(err)    }    fmt.Println(result)}

jedis

import java.net.URI;import redis.clients.jedis.Jedis;try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) {  Object result = jedis.append("my-key", "value");  System.out.println(result);}

redis-rs

use redis::TypedCommands;fn main() -> redis::RedisResult<()> {    let url = std::env::var("REDIS_URL").expect("REDIS_URL is not set");    let client = redis::Client::open(url)?;    let mut connection = client.get_connection()?;    let result = connection.append("my-key", "value")?;    println!("{result:?}");    Ok(())}