---
title: "Instant synchronization in Flutter | Authentication guide | Nutrient"
canonical_url: "https://www.nutrient.io/guides/flutter/instant-synchronization/authentication/"
md_url: "https://www.nutrient.io/guides/flutter/instant-synchronization/authentication.md"
last_updated: "2026-05-15T09:08:03.624Z"
description: "Authenticate your Flutter client with Nutrient Instant by generating a JSON Web Token (JWT). Access authorized data securely through Document Engine."
---

# Client authentication in Nutrient Instant

To use Nutrient Instant for Flutter, you have to authenticate your client with your running Document Engine instance. This can be done by [generating a JSON Web Token (JWT)](https://www.nutrient.io/guides/document-engine/viewer/client-authentication/generate-a-jwt.md) and sending it to the client. In most cases, your backend application will generate and send the JWT to the client. The client can then use the JWT to authenticate itself with Document Engine, which will return only the data that the user is authorized to view.

A JWT typically grants access to a specific document and [Instant layer](https://www.nutrient.io/api/reference/document-engine/upstream/#tag/Layers) combination. If you’re having difficulty generating valid JWTs, you can use the [Document Engine dashboard](https://www.nutrient.io/guides/document-engine/management/dashboard.md) to [validate](https://www.nutrient.io/guides/document-engine/viewer/client-authentication/validate-a-jwt.md) them.
---

## Related pages

- [Sync PDF annotations in Flutter apps](/guides/flutter/instant-synchronization/annotation-sync.md)
- [Adding Instant comments to PDFs in Flutter](/guides/flutter/instant-synchronization/comments.md)
- [PDF collaboration library for Flutter](/guides/flutter/instant-synchronization.md)
- [Instant sync and document state in Flutter](/guides/flutter/instant-synchronization/document-state.md)
- [NutrientInstantView widget](/guides/flutter/instant-synchronization/instant-view.md)
- [Integrating real-time collaboration into your Flutter application](/guides/flutter/instant-synchronization/get-started.md)
- [Create PDF annotation layers in Flutter](/guides/flutter/instant-synchronization/instant-layers.md)
- [Nutrient Instant usage](/guides/flutter/instant-synchronization/usage.md)
- [Offline PDF annotations with automatic sync](/guides/flutter/instant-synchronization/offline-support.md)