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Workers KV provides low-latency, high-throughput global storage to your Cloudflare Workers applications. Workers KV is ideal for storing user configuration data, routing data, A/B testing configurations and authentication tokens, and is well suited for read-heavy workloads.

This guide instructs you through:

• Creating a KV namespace.
• Writing key-value pairs to your KV namespace from a Cloudflare Worker.
• Reading key-value pairs from a KV namespace.

Prerequisites

1. Sign up for a Cloudflare account ↗.
2. Install Node.js ↗.

Node.js version manager

Use a Node version manager like Volta ↗ or nvm ↗ to avoid permission issues and change Node.js versions. Wrangler, discussed later in this guide, requires a Node version of 16.17.0 or later.

1. Create a Worker project

New to Workers?

Refer to How Workers works to learn about the Workers serverless execution model works. Go to the Workers Get started guide to set up your first Worker.

Create a new Worker to read and write to your KV namespace.

1. Create a new project named kv-tutorial by running:

   npm

   npm create cloudflare@latest -- kv-tutorial

   yarn

   yarn create cloudflare@latest kv-tutorial

   pnpm

   pnpm create cloudflare@latest kv-tutorial

   For setup, select the following options:

   • For What would you like to start with?, choose Hello World example.
   • For Which template would you like to use?, choose Hello World Worker.
   • For Which language do you want to use?, choose TypeScript.
   • For Do you want to use git for version control?, choose Yes.
   • For Do you want to deploy your application?, choose No (we will be making some changes before deploying).

   This creates a new kv-tutorial directory, illustrated below.

   • Directorykv-tutorial/

     • Directorynode_modules/

       • …
     • Directorytest/

       • …
     • Directorysrc

       • index.ts
     • package-lock.json
     • package.json
     • testconfig.json
     • vitest.config.mts
     • worker-configuration.d.ts
     • wrangler.toml

   Your new kv-tutorial directory includes:

   • A "Hello World" Worker in index.ts.
   • A wrangler.toml configuration file. wrangler.toml is how your kv-tutorial Worker accesses your kv database.

2. Change into the directory you just created for your Worker project:

   cd kv-tutorial

Note

If you are familiar with Cloudflare Workers, or initializing projects in a Continuous Integration (CI) environment, initialize a new project non-interactively by setting CI=true as an environmental variable when running create cloudflare@latest.

For example: CI=true npm create cloudflare@latest kv-tutorial --type=simple --git --ts --deploy=false creates a basic “Hello World” project ready to build on.

2. Create a KV namespace

A KV namespace is a key-value database replicated to Cloudflare’s global network.

You can create a KV namespace via Wrangler or the dashboard.

Create a KV namespace via Wrangler

Wrangler allows you to put, list, get, and delete entries within your KV namespace.

Note

KV operations are scoped to your account.

To create a KV namespace via Wrangler:

1. Open your terminal and run the following command:

   npx wrangler kv namespace create <YOUR_NAMESPACE>

   The npx wrangler kv namespace create <YOUR_NAMESPACE> subcommand takes a new binding name as its argument. A KV namespace is created using a concatenation of your Worker’s name (from your wrangler.toml file) and the binding name you provide. The id is randomly generated for you.

   npx wrangler kv namespace create <YOUR_NAMESPACE>

   🌀  Creating namespace with title <YOUR_WORKER-YOUR_NAMESPACE>
   ✨  Success!
   Add the following to your configuration file:
   kv_namespaces = [
     { binding = <YOUR_BINDING>, id = "e29b263ab50e42ce9b637fa8370175e8" }
   ]

2. In your wrangler.toml file, add the following with the values generated in your terminal:

   kv_namespaces = [
       { binding = "<YOUR_BINDING>", id = "<YOUR_ID>" }
   ]

   Binding names do not need to correspond to the namespace you created. Binding names are only a reference. Specifically:

   • The value (string) you set for <YOUR_BINDING> is used to reference this database in your Worker. In this tutorial, name your binding DB.
   • The binding must be a valid JavaScript variable name ↗. For example, binding = "MY_KV" or binding = "routingConfig" would both be valid names for the binding.
   • Your binding is available in your Worker at env.<YOUR_BINDING> from within your Worker.

Bindings

A binding is how your Worker interacts with external resources such as KV namespaces. A binding is a runtime variable that the Workers runtime provides to your code. You can declare a variable name in your wrangler.toml file that binds to these resources at runtime, and interact with them through this variable. Every binding’s variable name and behavior is determined by you when deploying the Worker.

Refer to Environment for more information.

Create a KV namespace via the dashboard

1. Log in to the Cloudflare dashboard ↗.

2. Select Workers & Pages > KV.

3. Select Create a namespace.

4. Enter a name for your namespace.

5. Select Add.

Note

KV namespaces prior to version 7 cannot be edited via the Cloudflare dashboard. To edit KV namespaces, use the KV API.

3. Interact with your KV namespace with Wrangler

You can interact with your KV namespace via Wrangler or directly from your Workers application.

Write a value via Wrangler

To write a value to your empty KV namespace using Wrangler:

1. Run the wrangler kv key put subcommand in your terminal, and input your key and value respectively. <KEY> and <VALUE> are values of your choice.

   npx wrangler kv key put --binding=<YOUR_BINDING> "<KEY>" "<VALUE>"

   Writing the value "<VALUE>" to key "<KEY>" on namespace e29b263ab50e42ce9b637fa8370175e8.

Instead of using --binding, you can also use --namespace-id to specify which KV namespace should receive the operation:

npx wrangler kv key put --namespace-id=e29b263ab50e42ce9b637fa8370175e8 "<KEY>" "<VALUE>"

Writing the value "<VALUE>" to key "<KEY>" on namespace e29b263ab50e42ce9b637fa8370175e8.

To create a key and a value in local mode, add the --local flag at the end of the command:

npx wrangler kv key put --namespace-id=xxxxxxxxxxxxxxxx "<KEY>" "<VALUE>" --local

Get a value via Wrangler

To access the value using Wrangler:

1. Run the wrangler kv key get subcommand in your terminal, and input your key value:

   # Replace [OPTIONS] with --binding or --namespace-id
   npx wrangler kv key get [OPTIONS] "<KEY>"

   A KV namespace can be specified in two ways:

   With a --binding

   npx wrangler kv key get --binding=<YOUR_BINDING> "<KEY>"

   With a --namespace-id

   npx wrangler kv key get --namespace-id=<YOUR_ID> "<KEY>"

You can add a --preview flag to interact with a preview namespace instead of a production namespace.

Warning

Exactly one of --binding or --namespace-id is required.

Note

To view the value directly within the terminal, add --text

Refer to the kv bulk documentation to write a file of multiple key-value pairs to a given KV namespace.

4. Access your KV namespace from a Worker

You can access the binding from within your Worker.

Note

When using wrangler dev to develop locally, Wrangler defaults to using a local version of KV to avoid interfering with any of your live production data in KV. This means that reading keys that you have not written locally returns null.

To have wrangler dev connect to your Workers KV namespace running on Cloudflare’s global network, call wrangler dev --remote instead. This uses the preview_id of the KV binding configuration in the wrangler.toml file. See the KV binding docs for more information.

1. In your Worker script, add your KV namespace in the Env interface:

   interface Env {
     YOUR_KV_NAMESPACE: KVNamespace;
     // ... other binding types
   }

2. Use the put() method on YOUR_KV_NAMESPACE to create a new key-value pair, or to update the value for a particular key:

   let value = await env.YOUR_KV_NAMESPACE.put(key, value);

3. Use the KV get() method to fetch the data you stored in your KV database:

   let value = await env.YOUR_KV_NAMESPACE.get("KEY");

Your Worker code should look like this:

export interface Env {
  YOUR_KV_NAMESPACE: KVNamespace;
}

export default {
  async fetch(request, env, ctx): Promise<Response> {
    try {
      await env.YOUR_KV_NAMESPACE.put("KEY", "VALUE");
      const value = await env.YOUR_KV_NAMESPACE.get("KEY");
      if (value === null) {
        return new Response("Value not found", { status: 404 });
      }
      return new Response(value);
    } catch (err) {
      // In a production application, you could instead choose to retry your KV
      // read or fall back to a default code path.
      console.error(`KV returned error: ${err}`);
      return new Response(err, { status: 500 });
    }
  },
} satisfies ExportedHandler<Env>;

The code above:

1. Writes a key to YOUR_KV_NAMESPACE using KV’s put() method.
2. Reads the same key using KV’s get() method, and returns an error if the key is null (or in case the key is not set, or does not exist).
3. Uses JavaScript’s try...catch ↗ exception handling to catch potential errors. When writing or reading from any service, such as Workers KV or external APIs using fetch(), you should expect to handle exceptions explicitly.

To run your project locally, enter the following command within your project directory:

npx wrangler dev

When you run wrangler dev, Wrangler provides a URL (usually a localhost:8787) to review your Worker. The browser prints your value when you visit the URL provided by Wrangler.

5. Deploy your KV

1. Run the following command to deploy KV to Cloudflare’s global network:

   npx wrangler deploy

2. Visit the URL for your newly created Workers KV application.

   For example, if the URL of your new Worker is kv-tutorial.<YOUR_SUBDOMAIN>.workers.dev, accessing https://kv-tutorial.<YOUR_SUBDOMAIN>.workers.dev/ sends a request to your Worker that writes (and reads) from Workers KV.

Summary

By finishing this tutorial, you have:

1. Created a KV namespace
2. Created a Worker that writes and reads from that namespace
3. Deployed your project globally.

Next steps

If you have any feature requests or notice any bugs, share your feedback directly with the Cloudflare team by joining the Cloudflare Developers community on Discord ↗.

• Learn more about the KV API.
• Understand how to use Environments with Workers KV.
• Read the Wrangler kv command documentation.