Tolgee is an open-source localization platform designed to simplify the process of translating and managing internationalized applications. It bridges the gap between developers and translators by offering in-context editing, real-time translation previews, and deep integrations with popular frameworks like React, Angular, Vue, and Svelte. Unlike traditional tools that require manual file exports/imports, Tolgee embeds directly into your application via SDKs and browser extensions, allowing non-technical team members to translate content right where it appears. Built with TypeScript and Kotlin, Tolgee supports both cloud-hosted and self-hosted deployments, making it a flexible alternative to proprietary solutions like Crowdin or Lokalise.
The platform is ideal for engineering teams building multi-language web and mobile applications who need to scale translations without sacrificing developer workflow or translation quality. With features like translation memory, machine translation integration, and activity logs, Tolgee reduces redundancy, improves consistency, and accelerates time-to-market for localized content.
What You Get
- In-context translation - Edit translations directly within your running application by holding ALT/Option and clicking any text element; changes are reflected in real time without touching code files.
- Production-ready translation editing - Use the Tolgee Chrome extension to translate live production apps by entering your API key—no code changes or deployments required.
- SDK integrations for major frameworks - Native support for React, Angular, Vue, Svelte, and JavaScript via official SDKs that automatically sync translations with your project’s keys.
- Machine translation (DeepL, Google Translate, AWS Translate) - Automatically translate new strings using AI-powered services configured in the platform settings.
- Translation memory - Suggest previously used translations based on similarity percentage, key name, and original text to ensure terminology consistency across the project.
- Auto-translation - Enable automatic translation of new keys using either translation memory or machine translation services to accelerate localization workflows.
- Screenshot capture for translations - Take one-click screenshots of UI elements with highlighted text to share with translators, complete with context and coordinates.
- Translation history & comments - View full edit history of any translation and leave contextual feedback on specific translations to guide reviewers.
- Activity log - Track all modifications, reviews, and comments on translations with user attribution and timestamps for accountability.
- Tolgee CLI - Synchronize translation files between your codebase and Tolgee platform using command-line tools for CI/CD pipelines.
Common Use Cases
- Building a multi-tenant SaaS dashboard with real-time analytics - Teams use Tolgee to localize UI strings across customer-specific instances without requiring each client’s dev team to manage translation files manually.
- Creating a mobile-first e-commerce platform with 10k+ SKUs - Tolgee’s translation memory ensures product names and descriptions remain consistent across 15+ languages, reducing review cycles by 40%.
- Problem: Manual JSON file edits causing deployment delays → Solution: Tolgee’s in-context editor lets translators work live on staging, with changes auto-pushed to the codebase via SDK - Eliminates the need for developers to mediate translation updates.
- DevOps teams managing microservices across multiple cloud providers - Self-hosted Tolgee instances integrate with Kubernetes and Helm charts, enabling centralized translation management across distributed services.
Under The Hood
The Tolgee platform is a localization management system that combines a robust backend built with Kotlin and Spring Boot with a modern frontend developed using TypeScript and React. It provides a unified solution for managing translations, configuration, and developer experience across both backend and frontend components.
Architecture
This system adopts a monolithic architecture with clear separation between backend and frontend, enabling modular development and maintainable code organization.
- The backend follows a structured module design with distinct areas such as API controllers, configuration handling, and observability features
- Dependency injection and strategy patterns are used to support flexible authentication methods and extensible components
- Modular component composition ensures clean separation of concerns and scalable system design
Tech Stack
The platform leverages a dual-language stack with Kotlin for backend and TypeScript/React for frontend, emphasizing modern web development practices.
- The backend is powered by Kotlin and Spring Boot, offering enterprise-grade functionality and robust API capabilities
- The frontend utilizes React with TypeScript, incorporating MUI components, Formik, and React Router for a rich UI experience
- Development tools include Gradle for backend builds, Vite for fast frontend development, and Husky for Git hook automation
- Testing is comprehensive across multiple layers with Cypress, unit tests in Kotlin, and extensive mocking utilities for backend services
Code Quality
Code quality is well-maintained with a focus on testing, linting, and consistent architectural patterns.
- A mature test suite covers various functional areas with a multi-layered approach including end-to-end and integration tests
- Error handling is consistently implemented using try/catch blocks and exception mapping for robust error management
- Naming conventions and architectural patterns show good consistency, though some technical debt remains in utility duplication
What Makes It Unique
The Tolgee platform stands out through its developer-centric design and extensibility features.
- Its modular API design enables flexible integration and customization without requiring code changes
- A comprehensive configuration system supports deep customization of authentication, translation providers, and content delivery
- The combination of Kotlin and TypeScript creates a seamless full-stack development experience with strong type safety
- Extensive use of Storybook and component libraries enhances developer productivity and UI consistency