# Kafka producer CLI tutorial

*Learn how to produce messages to Kafka using kafka-console-producer*

The `kafka-console-producer` CLI reads data from standard input and publishes it to Kafka topics. It's essential for testing, debugging, and quick data injection.

**What you'll learn:**
- How to send messages to a Kafka topic
- How to produce messages with keys
- How to produce messages from a file
- Important producer options and settings

> Use CLI commands with appropriate extensions for your platform: for Windows - `kafka-console-producer.bat`, for Mac and Linux - `kafka-console-producer.sh`.

## How to produce a message into a Kafka topic using the CLI?

To produce to a Kafka topic, we need to provide the mandatory parameters:

*   Find your Kafka hostname and port e.g., `localhost:9092`
*   If Kafka v2.5+, use the `--bootstrap-server` option
*   If older version of Kafka, use the `--broker-list` option
*   Provide the mandatory parameters: topic name
*   Use the `kafka-console-producer.sh` CLI as outlined below

### Example

Make sure the topic first_topic is already created with 3 partitions and a replication factor of 1:

```
kafka-topics --bootstrap-server localhost:9092 --topic first_topic --create --partitions 3 --replication-factor 1
```

Start producing to the topic:

**Kafka v2.5+**:

```
kafka-console-producer --bootstrap-server localhost:9092 --topic first_topic
```

**Kafka v2.4 or less:**

```
kafka-console-producer --broker-list localhost:9092 --topic first_topic
```

To exit the Kafka console producer, use the keyboard combination `Ctrl+C`.

### Command output

```
>
```

After the producer is opened, you should see a `>` sign. Then any line of text you write afterwards will be sent to the Kafka topic (when pressing `Enter`)

```
$ kafka-console-producer --bootstrap-server localhost:9092 --topic first_topic
>Hello World
>My name is Conduktor
>I love Kafka
>^C  (<- Ctrl + C is used to exit the producer)
```

### Gotchas

Here are the common mistakes and caveats with the `kafka-console-producer.sh` command:

*   Messages are sent with the `null` key by default (see below for more options)

*   **If the topic does not exist, it can be auto-created by Kafka:**

A topic with the name provided should exist. If you specify a topic that does not exist yet, a new topic with the name provided will be created with the **default number of partitions and replication factor.**

These are controlled by the broker-side settings (in your `config/server.properties` file), with the following defaults:

```
auto.create.topics.enable=true
num.partitions=1
default.replication.factor=1
```

### Extra important options you can set (advanced)

`--compression-codec`

To enable message compression, default `gzip`, possible values `'none'`, `'gzip', 'snappy', 'lz4', or 'zstd'`

`--producer-property`

To pass in any producer property, such as the `acks=all` setting

`--request-required-acks`

An alternative to set the `acks` setting directly

## How to produce messages from a file with the Kafka console producer CLI?

Example file `topic-input.txt` (make sure each message is on a new line)

```
Hello World
My name is John
```

Produce messages to the topic from the file (see the end of the command)

```
kafka-console-producer --bootstrap-server localhost:9092 --topic first_topic < topic-input.txt
```

## How to produce messages with key in the Kafka console producer CLI?

By default messages sent to a Kafka topic will result in messages with `null` keys.

We have to use the properties `parse.key` and `key.separator` to send the key alongside messages.

In this example, the separator between the key and the value is: `:`

```
kafka-console-producer --bootstrap-server localhost:9092 --topic first_topic --property parse.key=true --property key.separator=:
```

Example input:

```
>example key:example value
>name:John
```

Do not forget to always include your key/value separator otherwise you will get an exception.

## Quick reference

| Operation | Command |
|-----------|---------|
| Basic produce | `kafka-console-producer --bootstrap-server localhost:9092 --topic NAME` |
| Produce with keys | `... --property parse.key=true --property key.separator=:` |
| With compression | `... --compression-codec snappy` |
| With acks=all | `... --producer-property acks=all` |
| From file | `... < filename.txt` |

> **See it in practice with Conduktor**
> [Conduktor Console](https://docs.conduktor.io/guide/manage-kafka/kafka-resources/topics) provides a visual interface for producing messages with full control over headers, keys, and serialization formats.

## Next steps

- [Consume messages](https://www.conduktor.io/kafka/kafka-consumer-cli-tutorial) you've just produced from the CLI
- [Understand producers](https://www.conduktor.io/kafka/kafka-producers) including message keys and partitioning