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Configuration

Wrangler optionally uses a wrangler.json/wrangler.toml 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

# Top-level 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

The configuration for a Worker can become complex when you define different environments, and each environment has its own configuration. There is a default (top-level) environment and 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 metrics to Cloudflare for this project.

  • site object optional deprecated

    • See the Workers Sites section below for more information. Cloudflare Pages and Workers Assets is preferred over this approach.

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 test and deploy your Worker. If you have a Worker that is only for scheduled events, you can set this to false. Defaults to true.

  • 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

    • Path to a custom tsconfig.

  • 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.

  • build Build optional

    • Configures a custom build step to be run by Wrangler when building your Worker. Refer to Custom builds.

  • no_bundle boolean optional

    • Skip internal build steps and directly deploy your Worker script. You must have a plain JavaScript Worker with no dependencies.

  • 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).

  • 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.

  • 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.

  • minify boolean optional

    • Minify the Worker script before uploading.

  • node_compat boolean optional

    • Deprecated — Instead, enable the nodejs_compat_v2 compatibility flag, which enables both built-in Node.js APIs, and adds polyfills as necessary. Setting node_compat = true will add polyfills for Node.js built-in modules and globals to your Worker's code, when bundled with Wrangler. This is powered by @esbuild-plugins/node-globals-polyfill which in itself is powered by rollup-plugin-node-polyfills ↗.

  • 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.

Usage model

As of March 1, 2024 the usage model configured in your Worker's configuration file will be ignored. The Standard usage model applies.

Some Workers Enterprise customers maintain the ability to change usage models. Your usage model must be configured through the Cloudflare dashboard by going to Workers & Pages > select your Worker > Settings > Usage Model.

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

    • A map of values to substitute when deploying your Worker.

  • 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 # 10% of requests are logged

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 30,000 milliseconds (30 seconds).

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 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.

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's client 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 will use this ID. Otherwise, it will use database_id. This option is required when using wrangler dev --remote.

    • 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.

  • 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_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" # Should be unique for each entry
new_classes = ["DurableObjectExample"] # Array of new classes


[[migrations]]
tag = "v2"
renamed_classes = [{from = "DurableObjectExample", to = "UpdatedName" }] # Array of rename directives
deleted_classes = ["DeprecatedClass"] # Array of deleted class names

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.toml 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:

# required for database drivers to function
compatibility_flags = ["nodejs_compat_v2"]


[[hyperdrive]]
binding = "<BINDING_NAME>"
id = "<ID>"

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>"


[[kv_namespaces]]
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 # Delay messages by 60 seconds before they are delivered to a consumer

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 # Delay retried messages by 2 minutes before re-attempting delivery

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>"


[[r2_buckets]]
binding = "<BINDING_NAME2>"
bucket_name = "<BUCKET_NAME2>"

Vectorize indexes

A Vectorize index allows you to insert and query vector embeddings for semantic search, classification and other vector search use-cases.

To bind Vectorize indexes to your Worker, assign an array of the below object to the vectorize key.

  • binding string required

    • The binding name used to refer to the bound index from your Worker code.

  • index_name string required

    • The name of the index to bind.

Example:

[[vectorize]]
binding = "<BINDING_NAME>"
index_name = "<INDEX_NAME>"

Service bindings

A service binding allows you to send HTTP requests to another Worker without those requests going over the Internet. The request immediately invokes the downstream Worker, reducing latency as compared to a request to a third-party service. Refer to About Service Bindings.

To bind other Workers to your Worker, assign an array of the below object to the services key.

  • binding string required

    • The binding name used to refer to the bound Worker.

  • service string required

    • The name of the Worker.

  • entrypoint string optional

    • The name of the entrypoint to bind to. If you do not specify an entrypoint, the default export of the Worker will be used.

Example:

[[services]]
binding = "<BINDING_NAME>"
service = "<WORKER_NAME>"
entrypoint = "<ENTRYPOINT_NAME>"

Static assets

Refer to Assets.

Analytics Engine Datasets

Workers Analytics Engine provides analytics, observability and data logging from Workers. Write data points to your Worker binding then query the data using the SQL API.

To bind Analytics Engine datasets to your Worker, assign an array of the below object to the analytics_engine_datasets key.

  • binding string required

    • The binding name used to refer to the dataset.

  • dataset string optional

    • The dataset name to write to. This will default to the same name as the binding if it is not supplied.

Example:

[[analytics_engine_datasets]]
binding = "<BINDING_NAME>"
dataset = "<DATASET_NAME>"

mTLS Certificates

To communicate with origins that require client authentication, a Worker can present a certificate for mTLS in subrequests. Wrangler provides the mtls-certificate command to upload and manage these certificates.

To create a binding to an mTLS certificate for your Worker, assign an array of objects with the following shape to the mtls_certificates key.

  • binding string required

    • The binding name used to refer to the certificate.

  • certificate_id string required

    • The ID of the certificate. Wrangler displays this via the mtls-certificate upload and mtls-certificate list commands.

Example of a Wrangler configuration file that includes an mTLS certificate binding:

[[mtls_certificates]]
binding = "<BINDING_NAME1>"
certificate_id = "<CERTIFICATE_ID1>"


[[mtls_certificates]]
binding = "<BINDING_NAME2>"
certificate_id = "<CERTIFICATE_ID2>"

mTLS certificate bindings can then be used at runtime to communicate with secured origins via their fetch method.

Workers AI

Workers AI allows you to run machine learning models, on the Cloudflare network, from your own code – whether that be from Workers, Pages, or anywhere via REST API.

Unlike other bindings, this binding is limited to one AI binding per Worker project.

  • binding string required

    • The binding name.

Example:

[ai]
binding = "AI" # available in your Worker code on `env.AI`

Assets

Static assets allows developers to run front-end websites on Workers. You can configure the directory of assets, an optional runtime binding, and routing configuration options.

You can only configure one collection of assets per Worker.

The following options are available under the assets key.

  • directory string required

    • Folder of static assets to be served.

  • binding string optional

    • The binding name used to refer to the assets. Optional, and only useful when a Worker script is set with main.

  • html_handling: "auto-trailing-slash" | "force-trailing-slash" | "drop-trailing-slash" | "none" optional, defaults to "auto-trailing-slash"

    • Determines the redirects and rewrites of requests for HTML content. Learn more about the various options in assets routing.

  • not_found_handling: "single-page-application" | "404-page" | "none" optional, defaults to "none"

    • Determines the handling of requests that do not map to an asset. Learn more about the various options in assets routing.

Example:

assets = { directory = "./public", binding = "ASSETS", html_handling = "force-trailing-slash", not_found_handling = "404-page" }

Bundling

Wrangler can operate in two modes: the default bundling mode and --no-bundle mode. In bundling mode, Wrangler will traverse all the imports of your code and generate a single JavaScript "entry-point" file. Imported source code is "inlined/bundled" into this entry-point file.

It is also possible to include additional modules into your Worker, which are uploaded alongside the entry-point. You specify which additional modules should be included into your Worker using the rules key, making these modules available to be imported when your Worker is invoked. The rules key will be an array of the below object.

  • type string required

    • The type of module. Must be one of: ESModule, CommonJS, CompiledWasm, Text or Data.

  • globs string[] required

    • An array of glob rules (for example, ["**/*.md"]). Refer to glob ↗.

  • fallthrough boolean optional

    • When set to true on a rule, this allows you to have multiple rules for the same Type.

Example:

rules = [
  { type = "Text", globs = ["**/*.md"], fallthrough = true }
]

Importing modules within a Worker

You can import and refer to these modules within your Worker, like so:

index.js
import markdown from "./example.md";


export default {
  async fetch() {
    return new Response(markdown);
  },
};

Find additional modules

Normally Wrangler will only include additional modules that are statically imported in your source code as in the example above. By setting find_additional_modules to true in your configuration file, Wrangler will traverse the file tree below base_dir. Any files that match rules will also be included as unbundled, external modules in the deployed Worker. base_dir defaults to the directory containing your main entrypoint.

See https://developers.cloudflare.com/workers/wrangler/bundling/ ↗ for more details and examples.

Local development settings

You can configure various aspects of local development, such as the local protocol or port.

  • ip string optional
  • IP address for the local dev server to listen on. Defaults to localhost.
  • port number optional
  • Port for the local dev server to listen on. Defaults to 8787.

  • local_protocol string optional

    • Protocol that local dev server listens to requests on. Defaults to http.

  • upstream_protocol string optional

    • Protocol that the local dev server forwards requests on. Defaults to https.

  • host string optional

    • Host to forward requests to, defaults to the host of the first route of the Worker.

Example:

[dev]
ip = "192.168.1.1"
port = 8080
local_protocol = "http"

Secrets

Secrets are a type of binding that allow you to attach encrypted text values to your Worker.

When developing your Worker or Pages Function, create a .dev.vars file in the root of your project to define secrets that will be used when running wrangler dev or wrangler pages dev, as opposed to using environment variables in wrangler.toml. This works both in local and remote development modes.

The .dev.vars file should be formatted like a dotenv file, such as KEY="VALUE":

.dev.vars
SECRET_KEY="value"
API_TOKEN="eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9"

You can set secrets per environment by creating additional files with the naming convention .dev.vars.<environment-name>. Like other environment variables, secrets are non-inheritable and must be defined per environment.

Module Aliasing

You can configure Wrangler to replace all calls to import a particular package with a module of your choice, by configuring the alias field:

[alias]
"foo" = "./replacement-module-filepath"
replacement-module-filepath.js
export const bar = "baz";

With the configuration above, any calls to import or require() the module foo will be aliased to point to your replacement module:

import { bar } from "foo";


console.log(bar); // returns "baz"

Example: Aliasing dependencies from NPM

You can use module aliasing to provide an implementation of an NPM package that does not work on Workers — even if you only rely on that NPM package indirectly, as a dependency of one of your Worker's dependencies.

For example, some NPM packages depend on node-fetch ↗, a package that provided a polyfill of the fetch() API, before it was built into Node.js.

node-fetch isn't needed in Workers, because the fetch() API is provided by the Workers runtime. And node-fetch doesn't work on Workers, because it relies on currently unsupported Node.js APIs from the http/https modules.

You can alias all imports of node-fetch to instead point directly to the fetch() API that is built into the Workers runtime:

[alias]
"node-fetch" = "./fetch-nolyfill"
./fetch-nolyfill
export default fetch;

Example: Aliasing Node.js APIs

You can use module aliasing to provide your own polyfill implementation of a Node.js API that is not yet available in the Workers runtime.

For example, let’s say the NPM package you rely on calls fs.readFile ↗. You can alias the fs module by adding the following to your Worker’s wrangler.toml:

[alias]
"fs" = "./fs-polyfill"
./fs-polyfill
export function readFile() {
  // ...
}

In many cases, this allows you to work provide just enough of an API to make a dependency work. You can learn more about Cloudflare Workers' support for Node.js APIs on the Cloudflare Workers Node.js API documentation page.

Source maps

Source maps translate compiled and minified code back to the original code that you wrote. Source maps are combined with the stack trace returned by the JavaScript runtime to present you with a stack trace.

Example:

upload_source_maps = true

Workers Sites

Workers Sites allows you to host static websites, or dynamic websites using frameworks like Vue or React, on Workers.

  • bucket string required

    • The directory containing your static assets. It must be a path relative to your Wrangler configuration file.

  • include string[] optional

    • An exclusive list of .gitignore-style patterns that match file or directory names from your bucket location. Only matched items will be uploaded.

  • exclude string[] optional

    • A list of .gitignore-style patterns that match files or directories in your bucket that should be excluded from uploads.

Example:

[site]
bucket = "./public"
include = ["upload_dir"]
exclude = ["ignore_dir"]

Proxy support

Corporate networks will often have proxies on their networks and this can sometimes cause connectivity issues. To configure Wrangler with the appropriate proxy details, use the below environmental variables:

  • https_proxy
  • HTTPS_PROXY
  • http_proxy
  • HTTP_PROXY

To configure this on macOS, add HTTP_PROXY=http://<YOUR_PROXY_HOST>:<YOUR_PROXY_PORT> before your Wrangler commands.

Example:

Terminal window
$ HTTP_PROXY=http://localhost:8080 wrangler dev

If your IT team has configured your computer's proxy settings, be aware that the first non-empty environment variable in this list will be used when Wrangler makes outgoing requests.

For example, if both https_proxy and http_proxy are set, Wrangler will only use https_proxy for outgoing requests.

Source of truth

We recommend treating your Wrangler configuration file as the source of truth for your Worker configuration, and to avoid making changes to your Worker via the Cloudflare dashboard if you are using Wrangler.

If you need to make changes to your Worker from the Cloudflare dashboard, the dashboard will generate a TOML snippet for you to copy into your Wrangler configuration file, which will help ensure your Wrangler configuration file is always up to date.

If you change your environment variables in the Cloudflare dashboard, Wrangler will override them the next time you deploy. If you want to disable this behavior, add keep_vars = true to your Wrangler configuration file.

If you change your routes in the dashboard, Wrangler will override them in the next deploy with the routes you have set in your Wrangler configuration file. To manage routes via the Cloudflare dashboard only, remove any route and routes keys from your Wrangler configuration file. Then add workers_dev = false to your Wrangler configuration file. For more information, refer to Deprecations.

Wrangler will not delete your secrets (encrypted environment variables) unless you run wrangler secret delete <key>.

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