Opening a PDF on Android sometimes means accepting that the app has made a quiet pact with a remote server. The most popular file explorers ask for access to storage, network, even your contacts. What if a single 15 MB APK could read all your documents without ever touching the internet or requesting a single permission? That’s exactly the promise of Gander, a permission-free Android file viewer that’s already generating buzz in the open source community.
What is Gander?
Gander is a file viewer for Android developed by “mokshablr”, released under the MIT license. The project is hosted on GitHub and positions itself as a radical alternative to mainstream apps: one single tool, zero permissions, no network access.
The name comes from the English expression “take a gander”, meaning “to have a look”. And that’s precisely what the app does: it displays your files, period. No account to create, no cloud sync, no ads, no telemetry. The code is open, the APK weighs about 15 MB, and it runs on Android 8.0 and all later versions.
Launched in late July 2026 on Hacker News in a “Show HN” thread, the project found its audience immediately. A high score and dozens of technical comments confirmed the appetite among privacy-conscious users for tools that respect their privacy by design.
The zero-permission promise: how does it work?
On Android, an app that asks for nothing is rare. Most document viewers require at least storage access. Gander completely bypasses this logic thanks to two system-level mechanisms.
First, the app receives files through the Storage Access Framework (SAF) and “Open with” intents. In practice, Android itself hands Gander the document you selected, and only that one. The app never sees the rest of your file tree.
Second, for rendering office formats (Word, Excel, PowerPoint), Gander uses a sandboxed WebView. The necessary JavaScript libraries are bundled inside the APK, and the WebViewAssetLoader engine intercepts every request to serve it from local assets. Not a single byte goes over the network, and the INTERNET permission isn’t even declared in the manifest.
In plain terms: there’s nothing to audit, nothing to trust. The app can’t phone home because it simply lacks the technical ability to do so.
Supported formats
Gander covers a surprisingly wide range for such a lightweight app. Here’s what you can open:
Documents
- PDF (via Pdfium, native engine)
- Word .docx (offline rendering in WebView)
- Excel .xlsx, .xls, .xlsm, .csv, .ods (via SheetJS)
- PowerPoint .pptx (via PPTXjs)
Images
- JPEG, PNG, WebP, BMP, HEIC/HEIF
- Animated GIF, SVG, AVIF, ICO
- Deep zoom with tiled decoding for very large photos
Video and audio
- MP4, MKV, MOV, WebM, AVI, 3GP
- MP3, AAC, FLAC, WAV, OGG, Opus
- Playback via Media3 ExoPlayer, Android’s standard engine
Text and code
- Markdown with formatted HTML rendering
- Text files, JSON, XML, logs, source code
Legacy .doc and .ppt formats are not supported. The app states this clearly: no reliable offline rendering engine exists for these binary formats, and it suggests re-saving them as .docx or .pptx.
Installation and usage
Gander is not on the Play Store. That’s a deliberate choice: the app is distributed via GitHub releases, like many open source projects that take software sovereignty seriously.
The process is straightforward:
- Download the latest APK from the Releases page of the GitHub repository. The arm64 build fits nearly every phone made since 2017.
- Copy it to your phone, launch the installation, and allow unknown sources if you haven’t already.
- Play Protect may show an “unknown developer” warning. That’s normal for a sideloaded APK: just tap “Install anyway”.
For updates, you can install Obtainium and point it to the GitHub repository. The tool tracks tagged releases and updates Gander just like a store would.
Each release is signed with the same key. You can verify the certificate fingerprint before installing:
apksigner verify --print-certs Gander-x.y-arm64.apk
The official SHA-256 fingerprint is documented in the project’s README. If you care about mobile security, this step takes thirty seconds and guarantees the APK hasn’t been tampered with.
Folder browsing requires a one-time ACTION_OPEN_DOCUMENT_TREE authorization. Android refuses to grant the Downloads root to an app, so point it toward Documents, DCIM, or a subfolder inside Downloads instead.
Why Gander is a game changer for privacy
In an ecosystem where every app seems to want to vacuum up your data, Gander applies a simple principle: technical inability beats a promise. The absence of the INTERNET permission in the manifest isn’t a setting, it’s a structural guarantee.
The viewers built into phones often send your documents to cloud services for rendering. Gander does the opposite: the rendering libraries (Pdfium, SheetJS, docx-preview, PPTXjs, marked, DOMPurify) are all bundled locally. Sandboxing is handled by the built-in WebView browser, without ever hitting the network.
As a freelance security professional, this is exactly the kind of tool I recommend to my clients and use myself. No analytics, no accounts, no trackers. The code is auditable, the license is MIT, the dependencies are documented one by one with their respective licenses.
The developer has announced a roadmap that includes publishing on F-Droid and possibly an iOS version. For now, the Android version already does the job, and does it quite well.
Key takeaways
- Gander is an open source Android file viewer that reads PDF, Word, Excel, PowerPoint, photos, videos, audio, Markdown, and code in a single 15 MB app.
- It asks for strictly no permissions, including the INTERNET permission: it cannot communicate with the outside world by design.
- Document rendering is fully offline thanks to bundled JavaScript libraries and a sandboxed WebView.
- Installation is done via sideloaded APK from GitHub, with cryptographic signature verification available.
- It’s a young but already solid project, addressing a real need in the tech community: reading your files without compromising your privacy.
If you try Gander or have questions about mobile tools that genuinely respect confidentiality, feel free to reach out to me on the blog. I regularly share discoveries like this one.
Sources
- Official Gander GitHub repository: source code, documentation, releases, and detailed project architecture.