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Environment Variables and Contexts

deploy/reference/env_vars_and_contexts.md

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Environment variables in Deno Deploy allow you to configure your application with static values such as API keys or database connection strings.

Types of environment variables

Environment variables can be stored as:

  • Plain text: Visible in the UI and suitable for non-sensitive values like feature flags
  • Secrets: Never visible in the UI after creation, only readable from application code, suitable for sensitive values like API keys

Variables can be set at:

  • Application level: Specific to a single application
  • Organization level: Applied to all applications in the organization, but can be overridden by application-level variables

Contexts

Each environment variable applies to one or more contexts. Contexts represent the logical "environments" in which your code runs, each with its own set of variables and secrets.

By default, there are two contexts:

  • Production: Used for the production timeline serving production traffic
  • Development: Used for development timelines serving non-production traffic (preview URLs and branch URLs)

:::info

Need additional contexts? Please contact support.

:::

Additionally, there is a Build context used during the build process. Environment variables in the Build context are only available during builds and aren't accessible in Production or Development contexts (and vice versa). This separation enables different configuration for build-time vs. runtime.

Within a single application or organization, you cannot have multiple environment variables with the same name in the same context. You can, however, have variables with the same name in different non-overlapping contexts.

Adding, editing and removing environment variables

You can manage environment variables from several locations:

  • On the "New App" page while creating an application
  • In the application settings under the "Environment Variables" section
  • In the organization settings under the "Environment Variables" section

In each location, click the relevant edit button to open the environment variables drawer. Changes only apply when you click "Save." Clicking "Cancel" discards your changes.

To add a variable:

  1. Click "Add Environment Variable"
  2. Enter the name and value
  3. Specify whether it's a secret
  4. Select the contexts where it should apply

You can also bulk import variables from a .env file:

  1. Click "+ Add from .env file"
  2. Paste the contents of your .env file
  3. Click "Import variables"

Note that lines starting with # are treated as comments.

To remove a variable, click the "Remove" button next to it.

To edit a variable, click the "Edit" button next to it to modify its name, value, secret status, or applicable contexts.

Using environment variables in your code

Access environment variables using the Deno.env.get API:

ts
const myEnvVar = Deno.env.get("MY_ENV_VAR");
<!-- ## Exposing an environment variable as a file Environment variables can be exposed as a file instead of a regular environment variable by toggling the "Expose as file" option. When this option is enabled, the environment variable's value is stored in a temporary file in the application's file system. The environment variable then contains the file path to this temporary file instead of the value itself. To read the value, you can use the `Deno.readTextFile` API in combination with `Deno.env.get`: ```ts // Assuming MY_ENV_VAR is set to expose as a file const value = await Deno.readTextFile(Deno.env.get("MY_ENV_VAR")); ``` This is useful for values that are too large for environment variables or when you want to avoid exposing sensitive data in the environment variable list. Additionally it is useful for preexisting applications that expect certain environment variables to point to files, such as `PGSSLROOTCERT` for Postgres CA certificates. -->

Limits

Environment variables have the following limits:

  • Environment variable keys can be at most 128 bytes long.
  • Environment variable keys can not start with:
    • DENO_, except for DENO_AUTH_TOKENS, DENO_COMPAT, DENO_CONDITIONS, DENO_DEPLOY_ENDPOINT, or DENO_DEPLOY_TOKEN
    • LD_
    • OTEL_
  • Environment variable values can be at most 16 KB (16,384 bytes) long.
  • Environment variable keys can not be any of these keys. Instead, use Cloud Connections
    • AWS_ROLE_ARN
    • AWS_WEB_IDENTITY_TOKEN_FILE
    • GCP_WORKLOAD_PROVIDER_ID
    • GCP_SERVICE_ACCOUNT_EMAIL
    • GCP_PROJECT_ID
    • AZURE_CLIENT_ID
    • AZURE_TENANT_ID
    • AZURE_FEDERATED_TOKEN_FILE

Predefined environment variables

Deno Deploy provides these predefined environment variables in all contexts:

  • DENO_DEPLOY: true - Indicates that the code is running in Deno Deploy.
  • DENO_DEPLOY_ORGANIZATION_ID: The ID of the organization that owns the application. This is a UUID.
  • DENO_DEPLOY_ORGANIZATION_SLUG: The slug of the organization that owns the application. This is the human-readable identifier used in URLs that was set when creating the organization.
  • DENO_DEPLOY_APPLICATION_ID: The ID of the application. This is a UUID.
  • DENO_DEPLOY_APPLICATION_SLUG: The slug of the application. This is the human-readable identifier used in URLs that was set when creating the application, or changed later in the application settings.
  • DENO_DEPLOY_BUILD_ID: The ID of the currently running build.
  • DENO_DEPLOYMENT_ID: A unique identifier representing the entire configuration set (application ID, build ID, context, environment variables, cloud connections, database). Changes if any of these components change.
  • DENO_DEPLOY_BUILD_ID: The ID of the currently running revision.
  • DENO_TIMELINE: The timeline the application is currently running in. Possible values are production, git-branch/<branch-name>, and preview/<revision-id>. This is not set during builds, as builds are not specific to any timeline.

During builds, the environment variable CI=1 is additionally set.