> ## Documentation Index > Fetch the complete documentation index at: https://upstash.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # SET > Set string value. Use `SET` to store a string value at a key, replacing whatever was there before, whatever its type. By default the value is written unconditionally and the key's previous time to live is discarded. `KEEPTTL` preserves it, while `EX`, `PX`, `EXAT`, and `PXAT` attach a new lifetime in seconds or milliseconds, or an absolute deadline as a Unix timestamp. Setting the value and its expiration in one command is what keeps a key from ever existing without one. The condition decides whether the write happens at all. `NX` writes only when the key does not exist, which combined with an expiration is the standard way to acquire a lock, and `XX` writes only when it already exists, which refreshes a value without creating it. `IFEQ` and `IFNE` compare the current value with the one you supply, and `IFDEQ` and `IFDNE` compare its digest as returned by [`DIGEST`](/docs/redis/commands/string/digest), so a large value can be checked without sending it; these conditional forms are implemented by this Upstash deployment and give you compare-and-set semantics in a single command. `IFEQ` and `IFDEQ` require the key to exist, while `IFNE` and `IFDNE` also write when it does not. `GET` makes the reply the previous value instead of `OK`, which is how you swap a value and read what it replaced in one atomic step. When a condition prevents the write, the reply is null. ## Syntax ```redis theme={"system"} SET [NX | XX | IFEQ | IFNE | IFDEQ | IFDNE ] [GET] [EX | PX | EXAT | PXAT | KEEPTTL] ``` ## Arguments | Argument | Required | Repeatable | Description | | - | - | - | - | | `` | Yes | No | Redis key targeted by the command. | | `` | Yes | No | String value to store. | | `(NX \| XX \| IFEQ \| IFNE \| IFDEQ \| IFDNE )` | No | No | Choose one form: `NX` (only when the key does not exist); `XX` (only when it already exists); `IFEQ` (only when the current value equals ``); `IFNE` (only when it differs); `IFDEQ` (only when the current value's digest equals ``); `IFDNE` (only when it differs). | | `GET` | No | No | Also return the previous value. | | `(EX \| PX \| EXAT \| PXAT \| KEEPTTL)` | No | No | Choose one form: `EX` (set a lifetime in seconds); `PX` (set a lifetime in milliseconds); `EXAT` (expire at a Unix timestamp in seconds); `PXAT` (expire at a Unix timestamp in milliseconds); `KEEPTTL` (preserve the existing key lifetime). | ## Important points * `NX` and `XX` are mutually exclusive. * Choose at most one expiration form and at most one condition. `GET` changes a successful reply from `OK` to the previous value. * `IFEQ`/`IFNE` compare the current value; `IFDEQ`/`IFDNE` compare its digest. These conditional forms are implemented by this Upstash deployment. ## 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 | Simple string `OK`; with `GET`, the previous value as a bulk string, or Null bulk string or null array when the key did not exist or a condition failed | | RESP3 | Simple string `OK`; with `GET`, the previous value as a bulk string, or Null when the key did not exist or a condition failed | > [!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** > > ```bash theme={"system"} > SET my-key value > ``` > **@upstash/redis** > > ```ts theme={"system"} > import { Redis } from "@upstash/redis"; > > const redis = Redis.fromEnv(); > > await redis.set("my-key", {my: "value"}); > ``` > **upstash\_redis** > > ```python theme={"system"} > from upstash_redis import Redis > > redis = Redis.from_env() > result = redis.set("my-key", "value") > print(result) > ``` > **ioredis** > > ```ts theme={"system"} > import Redis from "ioredis"; > > const redis = new Redis(process.env.REDIS_URL!); > const result = await redis.set("my-key", "value"); > console.log(result); > ``` > **node-redis** > > ```ts theme={"system"} > import { createClient } from "redis"; > > const client = await createClient({ url: process.env.REDIS_URL }) > .on("error", console.error) > .connect(); > const result = await client.set("my-key", "value"); > console.log(result); > ``` > **redis-py** > > ```python theme={"system"} > import os > import redis > > client = redis.from_url(os.environ["REDIS_URL"]) > result = client.set("my-key", "value") > print(result) > ``` > **go-redis** > > ```go theme={"system"} > package main > > import ( > "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.Set(context.Background(), "my-key", "value", 0).Result() > if err != nil { > panic(err) > } > fmt.Println(result) > } > ``` > **jedis** > > ```java theme={"system"} > import java.net.URI; > > import redis.clients.jedis.Jedis; > > try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) { > Object result = jedis.set("my-key", "value"); > System.out.println(result); > } > ``` > **redis-rs** > > ```rust theme={"system"} > 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.set("my-key", "value")?; > println!("{result:?}"); > Ok(()) > } > ``` ## Related topics - [SET](/docs/redis/sdks/ts/commands/string/set.md) - [Set commands](/docs/redis/commands/set/overview.md) - [JSON.SET](/docs/redis/commands/json/json-set.md) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.