Write to the root service from a child component

In a hierarchical setup (provideChildTranslateService() for feature modules, provideTranslateService() for isolated subtrees), inject(TranslateService) returns the nearest service in the chain — not necessarily the root. v18 exposes getRoot() and getParent() for navigating the chain when needed.

When to use these

Need	API
Add a translation that all features can see	getRoot().setTranslation(...)
Read a translation that’s only on the root	getRoot().instant(...)
Walk the chain for debugging	getParent() in a loop until null
Check if you’re the root	service === service.getRoot()

getRoot() walks the parent chain until it hits an isolation boundary. For an isolated subtree (a provideTranslateService() nested inside another), it returns the subtree’s root — not the application-wide root. That’s by design: isolated subtrees should be independent.

Add a global translation from a feature module

import { Component, inject } from "@angular/core";
import { TranslateService } from "@ngx-translate/core";

@Component({
    selector: "app-feature-toolbar",
    template: `<button (click)="seedShared()">Seed shared keys</button>`,
})
export class FeatureToolbarComponent {
    private translate = inject(TranslateService);

    seedShared(): void {
        // Always lands on the root, regardless of where this component
        // sits in the service hierarchy.
        this.translate.getRoot().setTranslation(
            "en",
            { "shared.copyright": "© 2026 Acme" },
            true, // merge, don't replace
        );
    }
}

Walk the chain for debugging

import { inject } from "@angular/core";
import { TranslateService, ITranslateService } from "@ngx-translate/core";

let service: ITranslateService | null = inject(TranslateService);
while (service) {
    console.log(
        "layer:",
        service.currentLang(),
        service === service.getRoot() ? "(root)" : "",
    );
    service = service.getParent();
}

Notes

• getRoot() is cheap to call repeatedly (O(depth) walk, no caching needed in v18).
• getParent() returns null at an isolation boundary, even if there’s a provideTranslateService() further up the injector tree.
• If you find yourself reaching for getRoot() frequently in business logic, consider whether the data belongs on the root in the first place (provideTranslateService() at the app config) rather than being seeded from a child.