Gander: Zero-Permission, Offline File Viewer for Android
The open-source app renders diverse file formats locally without requesting system permissions or internet access.
Developer mokshablr has released Gander, an open-source Android application that allows users to view a wide variety of file formats without requiring any system permissions. The app is designed to operate entirely offline, providing a privacy-centric alternative to traditional document viewers.
Distributed as a small APK of approximately 15 MB, Gander supports a broad spectrum of content, including PDFs, Word (.docx), Excel (.xlsx), PowerPoint (.pptx), Markdown, plain text, code, and standard photo, video, and audio files. To ensure data privacy, the app does not declare the INTERNET permission, which prevents it from making direct network connections or exfiltrating data to external servers. The developer notes that the app cannot "phone home" because it lacks the necessary network permissions.
The Privacy Architecture
Android users typically face a choice between resource-heavy office suites that require accounts or lightweight third-party viewers that often request broad storage permissions. Some of these lightweight tools may process files in the cloud, creating potential privacy risks. Gander addresses this by utilizing the Android Storage Access Framework (SAF) and "Open with" intents. This architecture ensures the app only accesses specific documents that the user explicitly chooses to open, rather than requesting access to the entire device storage.
To handle complex Office formats without a network connection, Gander employs a sandboxed WebView. It uses WebViewAssetLoader to intercept requests and load bundled JavaScript libraries directly from the app's own assets, allowing for local rendering of spreadsheets and presentations. The application is compatible with Android 8.0 (API 26) and above.
Industry Implications
Gander demonstrates a "private by construction" approach to app design. By removing the network stack entirely and leveraging modern Android APIs, it provides a verifiable guarantee that user documents cannot be uploaded to a remote server. This is particularly significant for security-conscious users who frequently open files from untrusted sources and wish to avoid the risks associated with cloud-based rendering.
Future Outlook
As a project hosted on GitHub, Gander's open-source nature allows the community to verify its permission-less claims. The developer has noted on Hacker News that many other free viewers request broad storage access to upload files for rendering; Gander's local-first model serves as a proof of concept for more secure utility apps. Future updates may expand the list of supported formats or further optimize the sandboxed rendering engine.