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Configuration

Wrangler optionally uses a configuration file to customize the development and deployment setup for a Worker.

It is best practice to treat Wrangler's configuration file as the source of truth for configuring a Worker.

Sample Wrangler configuration

{
  "name": "my-worker",
  "main": "src/index.js",
  "compatibility_date": "2022-07-12",
  "workers_dev": false,
  "route": {
    "pattern": "example.org/*",
    "zone_name": "example.org"
  },
  "kv_namespaces": [
    {
      "binding": "<MY_NAMESPACE>",
      "id": "<KV_ID>"
    }
  ],
  "env": {
    "staging": {
      "name": "my-worker-staging",
      "route": {
        "pattern": "staging.example.org/*",
        "zone_name": "example.org"
      },
      "kv_namespaces": [
        {
          "binding": "<MY_NAMESPACE>",
          "id": "<STAGING_KV_ID>"
        }
      ]
    }
  }
}

Environments

You can define different configurations for a Worker using Wrangler environments. There is a default (top-level) environment and you can create named environments that provide environment-specific configuration.

These are defined under [env.<name>] keys, such as [env.staging] which you can then preview or deploy with the -e / --env flag in the wrangler commands like npx wrangler deploy --env staging.

The majority of keys are inheritable, meaning that top-level configuration can be used in environments. Bindings, such as vars or kv_namespaces, are not inheritable and need to be defined explicitly.

Further, there are a few keys that can only appear at the top-level.

Top-level only keys

Top-level keys apply to the Worker as a whole (and therefore all environments). They cannot be defined within named environments.

  • keep_vars boolean optional

    • Whether Wrangler should keep variables configured in the dashboard on deploy. Refer to source of truth.

  • migrations object[] optional

  • send_metrics boolean optional

    • Whether Wrangler should send usage data to Cloudflare for this project. Defaults to true. You can learn more about this in our data policy ↗.

  • site object optional deprecated

    • See the Workers Sites section below for more information. Cloudflare Pages and Workers Assets is preferred over this approach.
    • This is not supported by the Cloudflare Vite plugin.

Inheritable keys

Inheritable keys are configurable at the top-level, and can be inherited (or overridden) by environment-specific configuration.

  • name string required

    • The name of your Worker. Alphanumeric characters (a,b,c, etc.) and dashes (-) only. Do not use underscores (_).

  • main string required

    • The path to the entrypoint of your Worker that will be executed. For example: ./src/index.ts.

  • compatibility_date string required

    • A date in the form yyyy-mm-dd, which will be used to determine which version of the Workers runtime is used. Refer to Compatibility dates.

  • account_id string optional

    • This is the ID of the account associated with your zone. You might have more than one account, so make sure to use the ID of the account associated with the zone/route you provide, if you provide one. It can also be specified through the CLOUDFLARE_ACCOUNT_ID environment variable.

  • compatibility_flags string[] optional

    • A list of flags that enable features from upcoming features of the Workers runtime, usually used together with compatibility_date. Refer to compatibility dates.

  • workers_dev boolean optional

    • Enables use of *.workers.dev subdomain to deploy your Worker. If you have a Worker that is only for scheduled events, you can set this to false. Defaults to true. Refer to types of routes.

  • preview_urls boolean optional

    • Enables use of Preview URLs to test your Worker. Defaults to false. Refer to Preview URLs.

  • route Route optional

    • A route that your Worker should be deployed to. Only one of routes or route is required. Refer to types of routes.

  • routes Route[] optional

    • An array of routes that your Worker should be deployed to. Only one of routes or route is required. Refer to types of routes.

  • tsconfig string optional

  • triggers object optional

    • Cron definitions to trigger a Worker's scheduled function. Refer to triggers.

  • rules Rule optional

    • An ordered list of rules that define which modules to import, and what type to import them as. You will need to specify rules to use Text, Data and CompiledWasm modules, or when you wish to have a .js file be treated as an ESModule instead of CommonJS.
    • Not applicable if you're using the Cloudflare Vite plugin.

  • build Build optional

  • no_bundle boolean optional

    • Skip internal build steps and directly deploy your Worker script. You must have a plain JavaScript Worker with no dependencies.
    • Not applicable if you're using the Cloudflare Vite plugin.

  • find_additional_modules boolean optional

    • If true then Wrangler will traverse the file tree below base_dir. Any files that match rules will be included in the deployed Worker. Defaults to true if no_bundle is true, otherwise false. Can only be used with Module format Workers (not Service Worker format).
    • Not applicable if you're using the Cloudflare Vite plugin.

  • base_dir string optional

    • The directory in which module "rules" should be evaluated when including additional files (via find_additional_modules) into a Worker deployment. Defaults to the directory containing the main entry point of the Worker if not specified.
    • Not applicable if you're using the Cloudflare Vite plugin.

  • preserve_file_names boolean optional

    • Determines whether Wrangler will preserve the file names of additional modules bundled with the Worker. The default is to prepend filenames with a content hash. For example, 34de60b44167af5c5a709e62a4e20c4f18c9e3b6-favicon.ico.
    • Not applicable if you're using the Cloudflare Vite plugin.

  • minify boolean optional

  • keep_names boolean optional

    • Wrangler uses esbuild to process the Worker code for development and deployment. This option allows you to specify whether esbuild should apply its keepNames ↗ logic to the code or not. Defaults to true.

  • logpush boolean optional

    • Enables Workers Trace Events Logpush for a Worker. Any scripts with this property will automatically get picked up by the Workers Logpush job configured for your account. Defaults to false. Refer to Workers Logpush.

  • limits Limits optional

    • Configures limits to be imposed on execution at runtime. Refer to Limits.

  • observability object optional

    • Configures automatic observability settings for telemetry data emitted from your Worker. Refer to Observability.

  • assets Assets optional

    • Configures static assets that will be served. Refer to Assets for more details.

  • migrations object optional

    • Maps a Durable Object from a class name to a runtime state. This communicates changes to the Durable Object (creation / deletion / rename / transfer) to the Workers runtime and provides the runtime with instructions on how to deal with those changes. Refer to Durable Objects migrations.

Non-inheritable keys

Non-inheritable keys are configurable at the top-level, but cannot be inherited by environments and must be specified for each environment.

  • define Record<string, string> optional

  • vars object optional

  • durable_objects object optional

    • A list of Durable Objects that your Worker should be bound to. Refer to Durable Objects.

  • kv_namespaces object optional

    • A list of KV namespaces that your Worker should be bound to. Refer to KV namespaces.

  • r2_buckets object optional

    • A list of R2 buckets that your Worker should be bound to. Refer to R2 buckets.

  • vectorize object optional

    • A list of Vectorize indexes that your Worker should be bound to. Refer to Vectorize indexes.

  • services object optional

    • A list of service bindings that your Worker should be bound to. Refer to service bindings.

  • tail_consumers object optional

    • A list of the Tail Workers your Worker sends data to. Refer to Tail Workers.

Types of routes

There are three types of routes: Custom Domains, routes, and workers.dev.

Custom Domains

Custom Domains allow you to connect your Worker to a domain or subdomain, without having to make changes to your DNS settings or perform any certificate management.

  • pattern string required

    • The pattern that your Worker should be run on, for example, "example.com".

  • custom_domain boolean optional

    • Whether the Worker should be on a Custom Domain as opposed to a route. Defaults to false.

Example:

{
  "routes": [
    {
      "pattern": "shop.example.com",
      "custom_domain": true
    }
  ]
}

Routes

Routes allow users to map a URL pattern to a Worker. A route can be configured as a zone ID route, a zone name route, or a simple route.

Zone ID route

  • pattern string required

    • The pattern that your Worker can be run on, for example,"example.com/*".

  • zone_id string required

Example:

{
  "routes": [
    {
      "pattern": "subdomain.example.com/*",
      "zone_id": "<YOUR_ZONE_ID>"
    }
  ]
}

Zone name route

  • pattern string required

    • The pattern that your Worker should be run on, for example, "example.com/*".

  • zone_name string required

    • The name of the zone that your pattern is associated with. If you are using API tokens, this will require the Account scope.

Example:

{
  "routes": [
    {
      "pattern": "subdomain.example.com/*",
      "zone_name": "example.com"
    }
  ]
}

Simple route

This is a simple route that only requires a pattern.

Example:

{
  "route": "example.com/*"
}

workers.dev

Cloudflare Workers accounts come with a workers.dev subdomain that is configurable in the Cloudflare dashboard.

  • workers_dev boolean optional
    • Whether the Worker runs on a custom workers.dev account subdomain. Defaults to true.
{
  "workers_dev": false
}

Triggers

Triggers allow you to define the cron expression to invoke your Worker's scheduled function. Refer to Supported cron expressions.

  • crons string[] required
    • An array of cron expressions.
    • To disable a Cron Trigger, set crons = []. Commenting out the crons key will not disable a Cron Trigger.

Example:

{
  "triggers": {
    "crons": [
      "* * * * *"
    ]
  }
}

Observability

The Observability setting allows you to automatically ingest, store, filter, and analyze logging data emitted from Cloudflare Workers directly from your Cloudflare Worker's dashboard.

  • enabled boolean required

    • When set to true on a Worker, logs for the Worker are persisted. Defaults to true for all new Workers.

  • head_sampling_rate number optional

    • A number between 0 and 1, where 0 indicates zero out of one hundred requests are logged, and 1 indicates every request is logged. If head_sampling_rate is unspecified, it is configured to a default value of 1 (100%). Read more about head-based sampling.

Example:

{
  "observability": {
    "enabled": true,
    "head_sampling_rate": 0.1
  }
}

Custom builds

You can configure a custom build step that will be run before your Worker is deployed. Refer to Custom builds.

  • command string optional

    • The command used to build your Worker. On Linux and macOS, the command is executed in the sh shell and the cmd shell for Windows. The && and || shell operators may be used.

  • cwd string optional

    • The directory in which the command is executed.

  • watch_dir string | string[] optional

    • The directory to watch for changes while using wrangler dev. Defaults to the current working directory.

Example:

{
  "build": {
    "command": "npm run build",
    "cwd": "build_cwd",
    "watch_dir": "build_watch_dir"
  }
}

Limits

You can impose limits on your Worker's behavior at runtime. Limits are only supported for the Standard Usage Model. Limits are only enforced when deployed to Cloudflare's network, not in local development. The CPU limit can be set to a maximum of 300,000 milliseconds (5 minutes).

Each isolate has some built-in flexibility to allow for cases where your Worker infrequently runs over the configured limit. If your Worker starts hitting the limit consistently, its execution will be terminated according to the limit configured.


  • cpu_ms number optional
    • The maximum CPU time allowed per invocation, in milliseconds.

Example:

{
  "limits": {
    "cpu_ms": 100
  }
}

Bindings

Browser Rendering

The Workers Browser Rendering API allows developers to programmatically control and interact with a headless browser instance and create automation flows for their applications and products.

A browser binding will provide your Worker with an authenticated endpoint to interact with a dedicated Chromium browser instance.

  • binding string required
    • The binding name used to refer to the browser binding. The value (string) you set will be used to reference this headless browser in your Worker. The binding must be a valid JavaScript variable name ↗. For example, binding = "HEAD_LESS" or binding = "simulatedBrowser" would both be valid names for the binding.

Example:

{
  "browser": {
    "binding": "<BINDING_NAME>"
  }
}

D1 databases

D1 is Cloudflare's serverless SQL database. A Worker can query a D1 database (or databases) by creating a binding to each database for D1 Workers Binding API.

To bind D1 databases to your Worker, assign an array of the below object to the [[d1_databases]] key.

  • binding string required

    • The binding name used to refer to the D1 database. The value (string) you set will be used to reference this database in your Worker. The binding must be a valid JavaScript variable name ↗. For example, binding = "MY_DB" or binding = "productionDB" would both be valid names for the binding.

  • database_name string required

    • The name of the database. This is a human-readable name that allows you to distinguish between different databases, and is set when you first create the database.

  • database_id string required

    • The ID of the database. The database ID is available when you first use wrangler d1 create or when you call wrangler d1 list, and uniquely identifies your database.

  • preview_database_id string optional

    • The preview ID of this D1 database. If provided, wrangler dev uses this ID. Otherwise, it uses database_id. This option is required when using wrangler dev --remote.

  • migrations_dir string optional

    • The migration directory containing the migration files. By default, wrangler d1 migrations create creates a folder named migrations. You can use migrations_dir to specify a different folder containing the migration files (for example, if you have a mono-repo setup, and want to use a single D1 instance across your apps/packages).
    • For more information, refer to D1 Wrangler migrations commands and D1 migrations.

Example:

{
  "d1_databases": [
    {
      "binding": "<BINDING_NAME>",
      "database_name": "<DATABASE_NAME>",
      "database_id": "<DATABASE_ID>"
    }
  ]
}

Dispatch namespace bindings (Workers for Platforms)

Dispatch namespace bindings allow for communication between a dynamic dispatch Worker and a dispatch namespace. Dispatch namespace bindings are used in Workers for Platforms. Workers for Platforms helps you deploy serverless functions programmatically on behalf of your customers.

  • binding string required

    • The binding name. The value (string) you set will be used to reference this database in your Worker. The binding must be a valid JavaScript variable name ↗. For example, binding = "MY_NAMESPACE" or binding = "productionNamespace" would both be valid names for the binding.

  • namespace string required

  • outbound object optional

{
  "dispatch_namespaces": [
    {
      "binding": "<BINDING_NAME>",
      "namespace": "<NAMESPACE_NAME>",
      "outbound": {
        "service": "<WORKER_NAME>",
        "parameters": [
          "params_object"
        ]
      }
    }
  ]
}

Durable Objects

Durable Objects provide low-latency coordination and consistent storage for the Workers platform.

To bind Durable Objects to your Worker, assign an array of the below object to the durable_objects.bindings key.

  • name string required

    • The name of the binding used to refer to the Durable Object.

  • class_name string required

    • The exported class name of the Durable Object.

  • script_name string optional

    • The name of the Worker where the Durable Object is defined, if it is external to this Worker. This option can be used both in local and remote development. In local development, you must run the external Worker in a separate process (via wrangler dev). In remote development, the appropriate remote binding must be used.

  • environment string optional

    • The environment of the script_name to bind to.

Example:

{
  "durable_objects": {
    "bindings": [
      {
        "name": "<BINDING_NAME>",
        "class_name": "<CLASS_NAME>"
      }
    ]
  }
}

Migrations

When making changes to your Durable Object classes, you must perform a migration. Refer to Durable Object migrations.

  • tag string required

    • A unique identifier for this migration.

  • new_sqlite_classes string[] optional

    • The new Durable Objects being defined.

  • renamed_classes {from: string, to: string}[] optional

    • The Durable Objects being renamed.

  • deleted_classes string[] optional

    • The Durable Objects being removed.

Example:

{
  "migrations": [
    {
      "tag": "v1",
      "new_sqlite_classes": [
        "DurableObjectExample"
      ]
    },
    {
      "tag": "v2",
      "renamed_classes": [
        {
          "from": "DurableObjectExample",
          "to": "UpdatedName"
        }
      ],
      "deleted_classes": [
        "DeprecatedClass"
      ]
    }
  ]
}

Email bindings

You can send an email about your Worker's activity from your Worker to an email address verified on Email Routing. This is useful for when you want to know about certain types of events being triggered, for example.

Before you can bind an email address to your Worker, you need to enable Email Routing and have at least one verified email address. Then, assign an array to the object (send_email) with the type of email binding you need.

You can add one or more types of bindings to your Wrangler file. However, each attribute must be on its own line:

{
  "send_email": [
    {
      "name": "<NAME_FOR_BINDING1>"
    },
    {
      "name": "<NAME_FOR_BINDING2>",
      "destination_address": "<YOUR_EMAIL>@example.com"
    },
    {
      "name": "<NAME_FOR_BINDING3>",
      "allowed_destination_addresses": [
        "<YOUR_EMAIL>@example.com",
        "<YOUR_EMAIL2>@example.com"
      ]
    }
  ]
}

Environment variables

Environment variables are a type of binding that allow you to attach text strings or JSON values to your Worker.

Example:

{
  "name": "my-worker-dev",
  "vars": {
    "API_HOST": "example.com",
    "API_ACCOUNT_ID": "example_user",
    "SERVICE_X_DATA": {
      "URL": "service-x-api.dev.example",
      "MY_ID": 123
    }
  }
}

Hyperdrive

Hyperdrive bindings allow you to interact with and query any Postgres database from within a Worker.

  • binding string required

    • The binding name.

  • id string required

    • The ID of the Hyperdrive configuration.

Example:

{
  "compatibility_flags": [
    "nodejs_compat_v2"
  ],
  "hyperdrive": [
    {
      "binding": "<BINDING_NAME>",
      "id": "<ID>"
    }
  ]
}

Images

Cloudflare Images lets you make transformation requests to optimize, resize, and manipulate images stored in remote sources.

To bind Images to your Worker, assign an array of the below object to the images key.

binding (required). The name of the binding used to refer to the Images API.

{
  "images": {
    "binding": "IMAGES", // i.e. available in your Worker on env.IMAGES
  },
}

KV namespaces

Workers KV is a global, low-latency, key-value data store. It stores data in a small number of centralized data centers, then caches that data in Cloudflare’s data centers after access.

To bind KV namespaces to your Worker, assign an array of the below object to the kv_namespaces key.

  • binding string required

    • The binding name used to refer to the KV namespace.

  • id string required

    • The ID of the KV namespace.

  • preview_id string optional

    • The preview ID of this KV namespace. This option is required when using wrangler dev --remote to develop against remote resources. If developing locally (without --remote), this is an optional field. wrangler dev will use this ID for the KV namespace. Otherwise, wrangler dev will use id.

Example:

{
  "kv_namespaces": [
    {
      "binding": "<BINDING_NAME1>",
      "id": "<NAMESPACE_ID1>"
    },
    {
      "binding": "<BINDING_NAME2>",
      "id": "<NAMESPACE_ID2>"
    }
  ]
}

Queues

Queues is Cloudflare's global message queueing service, providing guaranteed delivery and message batching. To interact with a queue with Workers, you need a producer Worker to send messages to the queue and a consumer Worker to pull batches of messages out of the Queue. A single Worker can produce to and consume from multiple Queues.

To bind Queues to your producer Worker, assign an array of the below object to the [[queues.producers]] key.

  • queue string required

    • The name of the queue, used on the Cloudflare dashboard.

  • binding string required

    • The binding name used to refer to the queue in your Worker. The binding must be a valid JavaScript variable name ↗. For example, binding = "MY_QUEUE" or binding = "productionQueue" would both be valid names for the binding.

  • delivery_delay number optional

Example:

{
  "queues": {
    "producers": [
      {
        "binding": "<BINDING_NAME>",
        "queue": "<QUEUE_NAME>",
        "delivery_delay": 60
      }
    ]
  }
}

To bind Queues to your consumer Worker, assign an array of the below object to the [[queues.consumers]] key.

  • queue string required

    • The name of the queue, used on the Cloudflare dashboard.

  • max_batch_size number optional

    • The maximum number of messages allowed in each batch.

  • max_batch_timeout number optional

    • The maximum number of seconds to wait for messages to fill a batch before the batch is sent to the consumer Worker.

  • max_retries number optional

    • The maximum number of retries for a message, if it fails or retryAll() is invoked.

  • dead_letter_queue string optional

    • The name of another queue to send a message if it fails processing at least max_retries times.
    • If a dead_letter_queue is not defined, messages that repeatedly fail processing will be discarded.
    • If there is no queue with the specified name, it will be created automatically.

  • max_concurrency number optional

    • The maximum number of concurrent consumers allowed to run at once. Leaving this unset will mean that the number of invocations will scale to the currently supported maximum.
    • Refer to Consumer concurrency for more information on how consumers autoscale, particularly when messages are retried.

  • retry_delay number optional

Example:

{
  "queues": {
    "consumers": [
      {
        "queue": "my-queue",
        "max_batch_size": 10,
        "max_batch_timeout": 30,
        "max_retries": 10,
        "dead_letter_queue": "my-queue-dlq",
        "max_concurrency": 5,
        "retry_delay": 120
      }
    ]
  }
}

R2 buckets

Cloudflare R2 Storage allows developers to store large amounts of unstructured data without the costly egress bandwidth fees associated with typical cloud storage services.

To bind R2 buckets to your Worker, assign an array of the below object to the r2_buckets key.

  • binding string required

    • The binding name used to refer to the R2 bucket.

  • bucket_name string required

    • The name of this R2 bucket.

  • jurisdiction string optional

  • preview_bucket_name string optional

    • The preview name of this R2 bucket. If provided, wrangler dev will use this name for the R2 bucket. Otherwise, it will use bucket_name. This option is required when using wrangler dev --remote.

Example:

{
  "r2_buckets": [
    {
      "binding": "<BINDING_NAME1>",
      "bucket_name": "<BUCKET_NAME1>"
    },
    {
      "binding": "<BINDING_NAME2>",
      "bucket_name": "<BUCKET_NAME2>"
    }
  ]
}

Vectorize indexes