Remote Config parameters and conditions

Firebase Remote Config lets you dynamically control the behavior and appearance of your applications without requiring users to download an app update or requiring backend redeployments.

To configure your applications, you define parameters (key-value pairs) in Remote Config and consume them in your app or backend code. You can also define conditions (targeting rules) to assign conditional values that override default values for specific audiences, environments, or custom criteria.

Remote Config organizes parameters and conditions into templates. Depending on your architecture, you can use client templates, server templates, or both:

  • Parameters and conditions in client templates: Serve configurations to client app instances across Apple, Android, Web, Flutter, Unity, and C++ platforms. Target app instances using Google Analytics audiences, app versions, platform, device language, country, user percentiles, and client-side custom signals.

  • Parameters and conditions in server templates: Serve configurations to backend environments such as Cloud Run, Cloud Functions for Firebase, or containerized servers using the Firebase Admin SDK for Node.js, Python, Go, and Java. Evaluate parameters server-side with near-zero latency using server custom signals and random percentage rollouts.

Compare client and server templates

Client and server templates serve different architectures and support distinct SDKs and targeting rules. Use the following table to understand which template type fits your use case:

Feature Client templates Server templates
Target environments Client apps (Apple, Android, Web, Flutter, Unity, C++) Server environments (Cloud Run, Cloud Functions for Firebase, GKE, backend services)
Supported SDKs Firebase client SDKs Firebase Admin SDK (Node.js, Python, Go, Java)
Evaluation model Fetched and cached on client devices; activated by app code Loaded into server memory; evaluated per request with near-zero latency
Condition rules App version, OS/platform, device language, country/region, Analytics audiences and user properties, user in random percentile, first app open, client custom signals User in random percentage, server custom signals
Common use cases Feature rollouts, seasonal promotions, UI themes, A/B Testing, Personalization AI prompt and model selection, server-side feature flags, backend rate-limiting, dynamic routing
Detailed guide Parameters in client templates Parameters in server templates

Core concepts

Whether you work with client templates or server templates, Remote Config shares fundamental concepts:

Parameters

Parameters are key-value pairs that you define in the Firebase console or using the Remote Config backend APIs.

  • Parameter keys: String identifiers for your parameters. Keys can be up to 256 characters long, must start with an underscore or English letter character (A-Z, a-z), and can include numbers.
  • Parameter values: The values assigned to your parameters. Values are stored as strings, but you can select data types in the console to validate values against formats like String, Boolean, Number, or JSON.
  • Default values: The baseline value assigned when no condition rules apply. You can define in-app default values in your code, as well as template default values in the Remote Config backend.

Conditions, rules, and conditional values

Conditions let you target specific segments of app users or server requests with customized parameter values:

  • Rules: Individual criteria evaluated against client metadata or request contexts (such as a version number, country, or custom signal).
  • Conditions: Named sets of one or more rules. All rules within a condition must evaluate to true for the condition to evaluate to true.
  • Conditional values: Alternative values assigned to a parameter when a condition evaluates to true. If multiple conditions evaluate to true, the condition with the highest priority in the Firebase console takes precedence.

Parameter groups

To organize configurations with dozens or hundreds of parameters, you can use parameter groups. Groups provide visual organization in the Firebase console and logical grouping in the REST API.

  • A parameter can belong to only one group at a time.
  • Parameter keys remain globally unique across your project regardless of grouping.
  • Grouping doesn't change how parameter values are referenced in your SDK code.

For instructions on creating and managing groups, see the detailed client or server parameters guides.

Template versioning and rollbacks

Every time you update and publish parameters or conditions in Remote Config, Firebase creates and stores a new version of your template. You can view version history, compare changes between versions, and roll back to a previous version whenever necessary.

To learn more about template version management, see Manage Remote Config template versions.

Quotas and limits

Within a Firebase project, Remote Config enforces the following limits:

  • Parameters: Up to 3,000 parameters per project.
  • Conditions: Up to 2,000 conditions per project.
  • Parameter key length: Up to 256 characters.
  • Total value string length: Up to 1,000,000 characters across all parameter values within a project.

For a full list of limits, see Quotas and limits.

Next steps